SBMP/ CHEMISTRY DEPT.
Chapter 1
ATOMIC STRUCTURE
Define Atom : Atom is defined as the smallest particle of an element having all the properties of that
element.
Q1.) Describe Bohr’s Atomic theory.
State Bohr’s Postulates of Atomic Theory.
Write any 4 assumptions of Bohr’s Atomic Theory.
a) An Atom consists of a dense positively charged central part called nucleus and it is at rest.
b) The electrons revolve around the nucleus in fixed circular path
called orbit or shells. The
electrostatic force of attraction between the nucleus and electron is balanced by the centrifugal
force.
c) Out of the number of possible circular orbits around the nucleus the electrons revolve only in
certain permitted orbits called stationary states.
d) Each stationary state is associated with a definite amount of energy hence they are called energy
levels.
e) Electrons in energy level nearest to the nucleus have lower energy while those at a greater
distance from the nucleus have higher energy.
f) As long as the electron stays in same energy level the energy remains constant
g) An excited electron jumps from lower to higher level by absorbing energy and higher to lower
energy level by emitting energy.
h) The angular momentum of electron (mvr) must be an integral multiple of h/2π
mvr=nh/2π
where m -> mass of the electron v -> tangential velocity of the electron
r -> radius of the orbit h -> Plank’s constant n -> Principal quantum number
Q2.) Write a note on structure of a modern atom ?
Ans. Atom consists of subatomic particles i.e., electrons, protons , neutrons.
Protons and neutrons are present in nucleus and are called nucleons.
Protons are positively charged and neutrons are neutral.
Electrons revolve around the nucleus in circular path called orbits or shells.
electrons are negatively charged.
Atom as a whole is electrically neutral if an atom losses certain number of electrons then it becomes
positively charged. If an atom gains electrons then it becomes negatively charged.
Q3.) Why is atom electrically neutral ?
Ans.) Atom is electrically neutral because it contains equal number of positively charged protons and
negatively charged electrons.
Applied Chemistry / STRUCTURE of ATOM
Page No. 1
SBMP/ CHEMISTRY DEPT.
Q4.) Name the subatomic particles of an atom?
Ans.) Protons , neutrons and electrons are the subatomic or fundamental particles of an atom.
Q5.) State the characteristics of the following :Characteristics
Electron
proton
Neutron
Discoverer
Symbol
Nature
Location in an atom
Relative charge
Mass in a.m.u
J.JTHOMSAN
eNegatively
Extra nuclear part
-1
Appox . negligible
GOLDSTIEN
P
positively
nucleus
1
=1
CHADWICK
n
Neutral
Nucleus
0
=1
Q6.) Define
a) Atomic number (Z) :- Atomic number of an element is defined as the number of protons or
number of electrons present in an atom of that element.
Denoted as Z
Atomic no. (Z) =number or protons =number of electrons
Z= P = E
b.) Atomic mass number :- Atomic mass number of an element is defined as the sum of the
number of protons and neutrons present in an atom of that element .
atomic mass number =no . of protons + no . of neutrons
A=p+n
But number of protons = atomic number
p=Z
then A=z+n and n = A – Z
Q7.) Distinguish between atomic number and atomic mass number
ATOMIC NUMBER (Z)
ATOMIC MASS NUMBER (A)
THE NUMBER OF PROTONS OR
ELECTRONS PRESENT IN AN ATOM IS
CALLED ATOMIC NUMBER
THE SUM OF NUMBER OF PROTONS
AND NEUTRONS PRESENT IN AN ATOM
IS CALLED ATOMIC MASS NUMBER
DENOTED AS (Z) .
DENOTED AS (A)
IT FIXES THE POSITION OF AN
ELEMENT IN THE PERIODIC TABLE
IT DOES NOT FIX THE POSITION OF AN
ELEMENT IN THE PERIODIC TABLE
IT DOES NOT INDICATE THE MASS OF
AN ATOM
IT INDICATES THE MASS OF AN ATOM
Applied Chemistry / STRUCTURE of ATOM
Page No. 2
SBMP/ CHEMISTRY DEPT.
Q8.) State the number of electrons in the K,l,M,N shells of an atomic mass number and
neutrons?
Atomic number Z Atomic Mass Number A, Neutrons n
A= Z +n
n= A-Z
Q9) Why is the nucleus of an atom Positively charged?
Nucleus of an atom consists of neutrons and protons Neutrons are neutral in charge
where as protons are positively charged Hence nucleus of an atom is
Positively charged.
Q10) Why is the radius of a cation always smaller than its parent atom?
Cation is formed when an atom losses electrons the cation lasses
The valence electrons hence it loses the last orbit thus the size of the cation is reduced.
Therefore the radius of a cation is always smaller than its parent atom.
Q11). Solve the following
a).The nucleus consists of a Protons and 10 neutrons what should be its atomic weight and
electrochemical a nature.
No of Protons 9
No of neutrons 10
Atomic weight i.e. Atomic mass number = P+N
= 9+10
19
The atom is electronegative
b). For an element having atomic number 9 & mass number 19 write the number of protons
and neutrons in it ?
Atomic number Z = no of protons
Z=9 ; p=9
No of Neutrons (n)= A-Z
19-9
10
No of Protons=9, No of neutrons = 10
c) Calculate the atomic number and atomic mass number of an atom containing 19 electrons
and 20 neutrons
No. of electrons e =19
No. of neutrons n =20
Applied Chemistry / STRUCTURE of ATOM
Page No. 3
SBMP/ CHEMISTRY DEPT.
Atomic number (Z) number (Z)= No of electrons (e)
Z=19
Atomic mass number (a)=No of Protons + No of neutrons
A=P +N
But p=e, therefore p =19 ,A = 19+20 = 39
Q12). Which type of particles are responsible for the presence of Isotopes?
The neutral neutrons present in the nucleus of an atom are responsible for the presence of Isotopes
Q13). Distinguish Between Energy level & Sub energy level
Energy level
Bohr’s stationery orbits with definite amount
of energy is called as energy levels.
Sub energy level
The close grouping of a number of energy
levels in the main energy level are called sub
energy level.
They are denoted as K,L,M,N.
They are denoted as s,p,d,f.
Maximum number of electrons in the energy
Maximum number of electrons in sub energy
level “n” is given by 2n²
levels s=2,p=6,d=10,f=14
Energy levels are circular or elliptical in shape Sub energy level consists of orbitals having
different geometrical shapes
Q14). Define orbital
Orbital is defined as three dimensional region in space around the nucleus where the probability of
finding the electron is maximum,
Q15) Distinguish Between orbit & Orbital
Orbit
Orbit is fixed circular path around the nucleus
in which the electrons revolve.
They are designated as K,L,M,N.
Maximum number of electrons in an orbit is
given by 2n²
Orbits are circular an elliptical in shape.
Orbitals
Orbital is a three dimensional region in space
where the probability of finding an electron is
maximum.
They are designated as s,p,d,f.
Maximum number of electron in an orbital is
2.
Orbitals have different geometrical shapes.
Q16).state the maximum number of orbitals in the K,L,M,N shells of an atom .
Shell/energy level
Sub shells
No of orbitals
K
1s
1
L
2s2p
4
M
3s3p3d
9
N
4s4p4d4f
16
Applied Chemistry / STRUCTURE of ATOM
Page No. 4
SBMP/ CHEMISTRY DEPT.
Filling up of orbitals by electrons are guided by two rules.
Q17). State Hund’s rule of maximum multiplicity?
Ans). Hund’s rule of maximum multiplicity states that when several orbitals of same type are
available the electrons first fill all the orbitals with parallel spin before pairing in any one orbital.
Eg). ₆C
1s²,2s²,2p²
Eg). ₇N
1s²,2s²,2p³
Q18). Arrange the orbitals in the increasing order of energy
1s,2s,3s,4s,5s,6s,4f,3p,2p,3d,4d,5p,5d.
Ans). Arrangement of orbital sin the increasing order of energy are
1s<2s<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d.
Q19). State Aufbau’s Principle?
Aufbau’s principle states that electrons enter the orbital in the increasing order of energy. Hence
lower energy orbitals are filled first.
Q20). State Pauli’s Exclusion Principle.
Pauli’s exclusion principle states that no two electron in an atom can have all the four set of quantum
numbers same.
Q21.) Write a note on QUANTUM NUMBERS?
A complete representation of location and energy of an electron in an atom is given by a set of four quantum
numbers.
1 PRINCIPAL QUANTUM NUMBER
2 AZIMUTHAL QUANTUM NUMBER
3 MAGNETIC QUANTUM NUMBER
4 SPIN QUANTUM NUMBER
PRINCIPAL QUANTUM NUMBER (n) : describes the average distance of an electron cloud from the
nucleus. It is represented by n
Where n= 1,2,3,4,5,6 etc
i.e. shell K,L,M,N,O,P
AZIMUTHAL QUANTUM NUMBER(l) : describe the shape of electron cloud . its value depends upon the
value of (n) principal quantum number. It has all whole number values from 0 to n-1
i.e. l = 0,1,2,3,4…(n-1)
if n=1 then l=0 ( l= n-1= 1-1=0)
n=2 then l=0,1 (l = o,n-1= 2-1=1)
n=3 then =0,1 (l=0,n-1,2-1=1)
n=4 then l=0,1,2,3 (l=0,1,2,n-1 i.e. 4-1=3)
Each value of l represents a different subenergy level .the value of l is designated by the letters s,p,d,f
respectively.
i.e.
l= 0 , 1 , 2 , 3.
Applied Chemistry / STRUCTURE of ATOM
Page No. 5
SBMP/ CHEMISTRY DEPT.
Subenergy level
s , p , d , f.
MAGNETIC QUANTUM NUMBER (m) :-It describes orientation of electron cloud in space .
The values of m varies from -l to +l
i.e. m = 2l+1,
if l=0 then m=1
i.e. s-subenergy level ( 1 orbital).
If l=1 then m=3
i.e. p-subenergy level ( 3 orbitals).
If l=2 then m=5
i.e. d-subenergy level(5 orbitals).
If l=3 then m=7
i.e. f subenergy level (7 orbitals).
SPIN QUANTUM NUMBER(s) :-It describes the direction of spin of electron around its axis, i.e. clockwise (
) or anticlockwise( ).
It has only 2 values +1/2 and -1/2.
i.e. Only two electrons can be accommodated in an orbital with opposite spin ( ).
NUCLEAR STABILITY :-
Q22). What is Binding Energy?
Write a note on MASS DEFECT AND BINDING ENERGY:
Binding energy : Protons and neutrons are closely packed in nucleus .The protons present repel each other by
the electrostatic force of repulsion .Hence there must be extra energy supplied to bind the nucleons together in
the nucleus.
Definition : The energy required to bind the nucleons together in the nucleus is called as binding energy.
Mass defect: It is defined as the difference between the relative isotopic mass and the calculated mass of an
atom of an element.
Mass defect = Calculated mass - Relative isotopic mass .
Let 'A' be atomic mass number , 'Z' be atomic number and 'n' be number of neutrons .
Therefore, n=A-Z., mp, mn and me be masses of protons , neutrons and electrons respectively.
Calculated mass of atom = Z×mp+(A-Z)×mn+Z×me.
Let m be actual theoretical mass of an atom of an element then mass defect ( m).
( m) = [ Zmp+(A-Z)mn+Zme]-m.
= [Z(mp+me)+(A-Z)mn]-m. But mp+me=mH.
Therefore m= [ZmH+(A-Z)mn]-m.
Hence mass defect is the loss of mass which is given out in the form of energy called binding energy.When
there is a loss of 1 a.m.u then energy released is 931 m.e.v, Therefore
B.E= mass defect ×931. i.e. B.E= m×931.
Average B.E per nucleon = m*931/A m.e.v .
Applied Chemistry / STRUCTURE of ATOM
Page No. 6
SBMP/ CHEMISTRY DEPT.
Q23). State HEISENBERG'S UNCERTAINTY PRINCIPLE?
It States that it is not possible to determine simultaneously the position and momentum of a moving
microscopic particle with absolute accuracy.
Q24.) Write a note on Inert Gases?
 There are same elements which are not reactive at all they are called inert or noble element Eg. Helium
(He) ,Neon (Ne),Argon (Ar), Krypton (Kr), Xenon(Xe) , Radon (Rn),they have valency zero hence placed in
the zero group in the periodic table.
They have no tendency to lose or gain electrons as they have complete octet or duplet.
They do not undergo chemical reactions under normal conditions.
Q.25) Inert gas elements are also called zero group elements explain.
 Inert gas elements do not have the tendency to lose or gain electrons as their octet is
Complete hence they have valency zero. Thus they are called zero group elements.
Q.26) What is molecule ?
 Molecule is the smallest particle of a compound having all the properties of the compound.
Q.27) What is atomicity of a molecule ? State its types ?
Atomicity is the number of atoms in a molecule?
Atomicity
Monoatomic
Only 1 atom in the molecule
Diatomic
Two atoms in the molecule
Eg. Ar, Kr
Triatomic
Three atoms in the molecule
Eg. O2,Cl2
Eg. H2O,CO2
Q.28) Define a) Valence electrons b) Valency of element
 a) Valence electrons : the electrons present in the outermost orbit of an atom are called valence electrons or
valency electrons.
b) Valency of an element : The number of electrons an atoms can lose or gain or share so as to complete
its octet or duplet and become stable is called valency of an element.
Q.29) What is a chemical bond and state the type of chemical bond ?
 Chemical bond is the force of attraction between the atoms to hold them together as a stable molecule.
There are 3 type of chemical bonds.
1) Electrovalent bond
2) Covalent bond
3) Co-ordinate bond
Applied Chemistry / STRUCTURE of ATOM
Page No. 7
SBMP/ CHEMISTRY DEPT.
Q.30) State octet rule ?
 Law of octet or octet rule states that all elements have a tendency to acquire eight electrons I.e. octet in
their outer most orbit and become stable.
Q.31) State duplet rule ?
 Duplet rule state that an atom with only one orbit has a tendency to acquire 2 electrons i.e. duplet in that
orbit.
Q.32) Distinguish between Atom & Ion.
Atom
Atom is electrically neutral e.g. Na ,Cl.
Atom may or may not have free existence.
Atom may react with solvent .
Atom has incomplete outer most orbit. Except
inert gases.
Atom takes part in molecular reaction.
Ion
Ion has either positive or negative charge e.g.
Na+, Cl-.
Ions exist in pairs in solids & in solution they
are free.
Ions do not react with solvent.
Ions have complete outer most orbit.
Ions take part in ionic reaction.
Q.33) What is electro valency & explain its types ?
 Electro valency : The number of electrons that an atoms of an element gains or loses to complete its last
orbit is called electro valency .
Type of electro valency :
Positive electro valency :The valency obtained by loss of electrons from an atom to complete its outer most
orbit is called positive electro valency .
E.g.
Na+ + le-
Na
(2,8,1)
(2,8)
Mg++ + 2e-
Mg
(2,8,2)
(2,8)
Negative electro valency : The valency obtained by the gain of electrons by an atom to complete its outer
most orbit is called negative electro valency .
Eg. Cl
(2,8,7)
S
le-
+
(2,8,8)
+ 2e-
(2,8,6)
 Cl(2,8,8)

S-(2,8,8)
Q.34) Explain the formation of magnesium oxide.
 Magnesium oxide has molecular formula MgO ( 1 Mg atom & 1 oxygen atom)
Oxygen atom has atomic number 8 & electronic configuration (2,6)
Applied Chemistry / STRUCTURE of ATOM
Page No. 8
SBMP/ CHEMISTRY DEPT.
Number of valency electrons  6
Oxygen gains 2 electrons to complete its outer most orbit and attain stable electronic configuration of (2,8).
 O--
O + 2e(2,6)
(2,8)
Magnesium has atomic number 12 electronic configuration ( 2,8,2) no .of valence electrons 2
Magnesium loses two electrons to complete its outer most orbit and attain stable electronic configuration of
(2,8).
 Mg++ + 2e-
Mg
(2,8,2)
(2,8)
Mg
+
(2,8,2)

O
(2,6)
Mg++ + [ O ]- -  MgO
(2,8)
(2,8)
Magnesium oxide
The ions formed are held together by electrostatic force of attraction forming a electrovalent bond .
Q.35) Explain formation of aluminum chloride?
 Aluminum chloride has molecular formula AlCl3.
Aluminum
13Al
(2,8,3)
No. of valence electrons = 3
Aluminum loses 3 electrons to complete its outermost orbit & attain stable electronic configuration (2,8) &
form Al+++ ions.

Al
(2,8,3)
Al+++ + 3e(2,8)
The three electrons are received by three different chlorine atoms
Chlorine
17Cl
(2,8,7).
No. of valence electrons = 7
Chlorine gains 1 electrons to complete its outermost orbit & attain stable electronic configuration (2,8,8) &
form Chlorine ions ( Cl- ).
Hence 3 chlorine atoms are required to accept 3 electrons .
Cl
(2,8,7)
+ le-

Cl(2,8,8)
Applied Chemistry / STRUCTURE of ATOM
Page No. 9
SBMP/ CHEMISTRY DEPT.
Thus the 3 chlorine ions & one aluminum ion are held together by electrostatic force of attraction forming 3
electrovalent bonds .
[ Cl ]-
Cl
Al
Cl 
+
[ Al ]+++ + [
Cl
]-
Cl
 Al
Cl
Cl

[ Cl ]-
Cl
AlCl 3
Q.36) Explain the formation of calcium chloride ?
 Calcium chloride molecular formula CaCl2 it has 1 calcium atoms & 2 chlorine atoms .
Calcium
2OCa
 (2,8,8,2) .
No. of valance electrons 2
Calcium loses two electrons to become stable and attain electronic conflagration (2,8,8) and form Ca++ ions.

Ca
(2,8,8,2)
Ca ++ + 2e(2,8,8)
Two chlorine atoms gain one electron each in order to complete the outermost orbit and attain stable
electronic configuration (2,8,8) and form Cl- ions .
Cl
+
le-  Cl-
(2,8,7)
(2,8,8)
Cl
Ca
+ Cl
 Ca++ +
[ Cl
]-
[
]- 
Cl
Cl
Ca
Cl

CaCl2
Thus two chlorine ions (Cl-) and one calcium ion (Ca++) are held together by electro static force of attraction
forming 2 electrovalent bond.
Q.37) State the properties of a electrovalent compounds ?
 Electrovalent compound are soluble in water & they ionize in fused as well as solution state and conduct
electricity .
They have high melting and boiling points they are mostly inorganic compounds .
Q.38) What is covalency ?
Applied Chemistry / STRUCTURE of ATOM
Page No. 10
SBMP/ CHEMISTRY DEPT.
 The number of electrons pairs which an atom of an element shares with another similar or dissimilar atom
is called as covalency .
Q.39) Explain formation of chlorine molecule .
 Chlorine molecule consists of 2 chlorine atoms
 (2,8,7) No. of valence electrons 7 Chlorine requires 1 electron to complete its octet each chlorine
atom shares 1 electron with another chlorine atom and completes its octet .
17Cl
Cl + Cl 
 Cl – Cl  Cl2
Single covalent bond is formed between two chlorine atoms.
Q.40) Explain formation of methane molecule.
 Molecule of methone ( CH4 ) Consiste of 1 carbon atoms & 4 Hydrogen atoms.
Carbon atomic no. 6 ,electonic confligation (2,4)
No . of valence eletronce  4
Carbon requires 4 electrons to complete its octet hence it shares its 4 electrons with 4 different hydrogen
atoms.
Each hydrogen requires 1 electron to complete its duplet each hydrogen shares its 1 electron with the carbon
atom and completes its duplet thus forming 4 single covalent bonds.
Q.41) Explain the formation of Oxygen molecule ?
 Oxygen molecule consists of two oxygen atoms
Oxygen
8O
 (2,6) No. of valence electrons  6
Each oxygen atom requires 2 electrons to complete its octet.
Thus each oxygen shares its two electrons with another Oxygen atom thus 4 electrons are shared and a double
covalent bond is formed .
Applied Chemistry / STRUCTURE of ATOM
Page No. 11
SBMP/ CHEMISTRY DEPT.
Q.42) Explain formation of Nitrogen molecule ?
 Nitrogen molecule (N2) consists of 2 nitrogen atoms 7N (2,5) No. of valence electrons  5.
Each nitrogen atoms requires 3 electrons to complete its octet this N2 molecule is formed by sharing of 3 pair
of electrons between two nitrogen atoms.
Thus 3 pair of electrons (6e-s) shared forms a triple covalent bond .
Q43.) Explain the formation of ammonia molecule?
Ammonia molecule consists of a nitrogen atom and 3 hydrogen atoms.
N (2,5) No of valence electrons are 5.
H (1) No of valence electron is 1
Nitrogen requires 3 electrons to complete its octet hence it shares its 3 electrons with 3 different Hydrogen
atoms. And each Hydrogen atom shares 1 electron with the nitrogen atom. Thus 3 pairs of electrons i.e. 6
electrons are shared forming 3 covalent bonds.
Q.44) Explain the formation of water molecule?
(Self Study)
Q.45) State the properties of covalent compound ?
 Covalent compound are insoluble in water but soluble in organic solvents like benzene.
They do not ions in water and do not conduct electricity they have low melting & boiling point
mostly organic compounds.
they are
Q.46) Distinguish between electrovalent & covalent compound ?
Electro compound
They are formed by loss and gain of electrons
of an atom.
They are soluble in water.
They have high melting & boiling points .
Covalent compound
They are formed by sharing of electrons between
the atoms.
They are insoluble in water but soluble in organic
solvents.
They do not ionise in water & do not conduct
electricity.
They have low melting and boiling points.
They are mostly inorganic compounds .
They are mostly or genie compounds.
They ionise in water and conduct electricity.
Applied Chemistry / STRUCTURE of ATOM
Page No. 12
SBMP/ CHEMISTRY DEPT.
Chapter 2
ELECTROCHEMISTRY
Q.1)
Define Electrochemistry.
Electrochemistry is a branch of chemistry which deals with the study of chemical changes
produced by the passage of electric current and the production of electricity from chemical
changes.
Q.2)
Define: a) Conductors
b) Non conductors
a) Conductor:-it is a substance which allows the electric current to pass through it.
Eg:- Metals, aqueous solutions of acids or bases.
b) Non conductor :- it is a substance which do not allow the electric current to pass through it.
Eg:- Paper, Wood.
Q.3) Name the types of conductors.
There are two types of conductors; metallic conductors and electrolytic conductors.
Q.4) Distinguish between Metallic conductors and Electrolytic conductor.
Metallic Conductors
Electrolytic Conductors
1) Free electrons carry electric current.
1) Ions in the solution carry electric current.
2) No chemical reaction takes place.
2) Chemical reaction takes place.
3) No transfer of matter takes place
3) Matter is transferred in the form of ions.
4) If temperature increases conduction
decreases.
4) If temperature increases conduction
increases.
Q.5) Define a} Ionisation
b} Electrolytic dissociation
a} Ionisation: - The process of breaking up of a substance into charged atom (ions) or radicals
is known as ionisation.
b} Electrolytic Dissociation: - the process of splitting up of an electrovalent compound into
ions when dissolved in solvent like water is called electrolytic dissociation.
Q.6) Explain Arrhenius Theory of electrolytic dissociation/ ionization. OR Write any 4
assumption or postulates of Arrhenius theory.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 1
SBMP/ CHEMISTRY DEPT.
ANS:-A molecule of an electrovalent compound when dissolved in solvent splits into
positively charged cations and negatively charged anions.
Cations are generally metallic radicals obtained by loss of electrons by the metallic atoms.
Anions are generally non metallic radicals obtained by gain of electrons by non metallic
atoms.
The number of positive charges on cation and negative charges on anion are equal hence the
solution is electrically neutral .The number of positive and negative charges on the cation or
anion corresponds to the valency of the element from which the ions is derived.
The ions present in solution are constantly reuniting to form undissociated molecules.
E.g. HCl ⇌ H+ + Cl-
Q.7) Define degree of ionization/ dissociation and explain the factor affecting it.
ANS:- Degree of ionisation/dissociation:- the fraction of total number of molecules of an
electrolyte that ionises in solution is called degree of ionization/dissociation.
Degree of ionization =
Number of molecules ionised
Total number of molecules dissolved
Factors affecting the degree of ionisation.
1.Nature of solute:- Salts of strong acids like HCL, H2SO4 and strong bases like NaOH ,
KOH have high degree of ionisation salts of weak acids like CH3COOH and weak base
NH4OH have low degree of ionization.
2.Nature of solvent:- In polar solvents like water and ammonia degree of ionization is more.
In non polar solvents like chloroform degree of ionization is less.
3.Concentration of solution:- If concentration of solution is more degree of ionisation is less.
4.Temperaure:- If temperature increases degree of ionisation increases.
Q.8) Define a} Electrolyte,
b}Non electrolyte.
a} Electrolyte:- The substance which in fused state or in solution liberates ions and allows the
electric current to flow through it is called electrolyte.
b} Non electrolyte :- The substance which in fused state or in solution does not conduct
electric current is called non electrolyte.
Q.9) Name and define the types of electrolyte.
ANS:- There are two types of electrolytes a} Strong electrolytes b} Weak electrolytes.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 2
SBMP/ CHEMISTRY DEPT.
Strong electrolytes:- Electrolytes having high degree of ionisation are called strong
electrolytes.
Eg:- HCl, NaOH.
Weak electrolytes :- Electrolytes having low degree of ionisation are called weak electrolytes.
Eg:- CH3COOH , NH4OH.
Q.10) Define a} Electrolysis b} Electrode
c} Electrode potential
a} Electrolysis:- The process of chemical decomposition of an electrolyte by the passage of
electric current through it is called electrolysis.
b} Electrode :- These are metallic or non metallic plates or rods immersed in the electrolyte
and they conduct electricity in and out of solution.
c} Electrode potential :- When a metal rod is dipped in its salt solution de-electronation and
electronation reaction takes place hence an electrical double layer is formed at the junction of
the solution and the electrode hence the potential developed is called as electrode potential.
Q.11) Define a} Anode
b} Cathode.
Anode :- Anode is the electrode connected to the positive terminal of the battery.
Cathode :- Cathode is the electrode connected to the negative terminal of the battery.
Q.12) Explain electrolysis of copper sulphate using platinum electrode.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 3
SBMP/ CHEMISTRY DEPT.
Electrolysis of copper sulphate is carried out in glass container. Electrolyte is aqueous
sulphate(CuSO4). Electrodes: Two platinum electrodes (rods) one acts as anode and another
act as cathode.
As electric current is passed through the electrodes into the electrolyte dissociation of copper
sulphate takes place: CuSO4 ⇌ Cu++ + SO4- Water also dissociates under the influence of electric current:
H2O ⇌ H+ + OH-
At cathode :- both positively charged Cu++ and H+ ions migrate towards cathode and Cu++
ions accept electrons and settle at the cathode as Cu metal.
Reaction at cathode :- Reduction (Gain of electrons)
Cu++ + 2e-
→
(solution)
Cu↓
(cathode)
At anode:- Both negatively charged ions SO4- - And –OH migrate towards anode and (-OH)
liberates electrons and gets discharged.
Reaction at anode :- Oxidation ( Loss of electrons)
OH4OH
→
OH + 1e-
→ 2H2O + O2↑
Net result :- Copper is deposited at the cathode and oxygen is liberated at anode in the
solution the number of Cu++ ions goes on reducing and thus the solution slowly turn blue to
colourless.
Q.13) Explain the electrolysis of copper Sulphate using copper electrodes.
Electrolysis of copper sulphate is carried out in iron crucible, electrolyte is aqueous copper
sulphate (CuSO4)
Electrodes : Two copper electrodes(rods) one acts as cathode and another acts as anode.
As the electric current is passed through the electrodes into the electrolyte dissociation of
copper sulphate and water takes place.
CuSO4 →
H2O →
Cu++ + SO4- H+ + OH -
Cu++ and H+ migrate towards the cathode (Reduction)
At cathode :- Cu++ accepts electrons and deposits as Cu atom thus reduction takes place.
Cu++ + 2e-
→
Cu↓
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 4
SBMP/ CHEMISTRY DEPT.
(solution)
(at cathode)
SO4- - and OH- Migrate towards the anode.
At anode :- (Oxidation) Copper atoms present at the anode lose two electrons and come into
solution as copper ions
Cu
→
(Anode)
Cu++ + 2e(solution)
Net result :- Copper is deposited at the cathode hence size of the cathode increases.
copper ions enter the solution from the anode hence size of the anode decreases.
Since copper ions enter the solution continuously the solution remains unchanged.
Q.14) Define
a} Coulomb b} ampere c} faraday.
a}Coulomb : - It is the quantity of electricity that passes through a circuit when a current of
one ampere is passed through the circuit for one second.
Coulomb =Ampere × Second.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 5
SBMP/ CHEMISTRY DEPT.
b}Ampere :- It is the current which when passed through a circuit for one second liberates
0.0000104g of hydrogen.
c} Faraday :- It is the quantity of electricity required to liberate or deposit one gram
equivalent of a substance from its solution.
Q.15 ) State Faraday’s first law of Electrolysis.
ANS:- Faraday’s first law of electrolysis states that the weight of a substance liberated or
deposited at an electrode during electrolysis is directly proportional to the quantity of
electricity passed through the electrolyte.
WαQ
But Q =
Where
Q= number of coulombs(quantity of electricity)
c×t
c = current in amperes
Wαc×t
t = time in seconds, W= weight of substance
W= zct
z = constant i.e. : electrochemical equivalent
Q.16) Define electrochemical equivalent (ECE).
ANS :- Electrochemical equivalent of a substance is defined as the weight of a substance
liberated or deposited when 1 ampere current is passed through the circuit for 1 second.
We know W = zct
Where c = 1A , t = 1 sec then W = z.
Q.17) State Faraday’s second Law.
ANS:- Faraday’s second law state that when same quantity of electricity is passed through
different electrolytes arranged is series the weight of the substance liberated at the respective
electrodes are directly proportional to their chemical equivalent.
Weight of Ag deposited(W1 )
Chemical equivalent of Ag (E1 )
=
Weight of Cu deposited(W2 ) Chemical equivalent of Cu (E 2 )
W1
W2
=
E1
E2
Q.18) State the relation between electrochemical equivalent and chemical equivalent.
ANS:- Chemical equivalent (CE) = 96500 × ECE (electrochemical equivalent)
CE = 96500 ECE.
Q.19) State the relation between Faraday and coulomb.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 6
SBMP/ CHEMISTRY DEPT.
ANS:- Faraday and coulomb both are unit of charge .
1 Faraday = 96500 Coulomb.
IMPORTANT FORMULAE
1} W = zct
2}
W1 E 1
=
W2 E 2
3} Equivalent weight of metal =
Atomic wt.
Valency
4} CE = 96500 × ECE
5} 96500 coulombs of electricity liberates 1 gram equivalent weight of a substance.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 7
SBMP/ CHEMISTRY DEPT.
Applications of Electrolysis
Q.1) Explain the process of electroplating with an example.
ANS: - The process of coating an article with a metal with the help of electric current is
called electroplating.
Purpose of electroplating is:1) To protect active metal from corrosion
2) For decorative purpose
E.g.:- electroplating of an iron article with silver.
Procedure: - The article to be coated i.e. iron spoon is cleaned with water and is connected to
the negative terminal of the battery i.e. it acts as cathode.
The metal to be deposited i.e. Ag block acts as the anode.
Both the electrodes are dipped in the electrolyte i.e. a salt solution of the anodic metal i.e.
[KAg(CN)2]
On passing electric current Ag+ ions from solution get deposited at the cathode.
At Cathode:
Ag+ + 1e-
→
Ag↓
And at anode Ag atoms lose electrons and come in solution as Ag+ ions.
At Anode:
Ag↓
→
Ag+ + 1e-
Thus silver gets deposited on the cathode i.e. the article to be coated.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 8
SBMP/ CHEMISTRY DEPT.
Q.2) Explain the process of electrorefining of copper.
ANS: - The process of purification of a metal into its most purest form by passage of electric
current is called electrorefining.
Procedure: - In electrorefining of copper, impure copper plate is taken as anode. Pure copper
plate is taken as cathode. Copper sulphate is used as electrolyte both the electrode are dipped
in CuSO4 On passing electricity copper sulphate dissociates to form Cu++ ions and SO4- ions.
→
CuSO4
Cu++ + SO4- -
Copper ions formed moves towards cathode and gets discharged by accepting 2 electrons
hence pure copper gets deposited at the cathode.
Cu++ + 2e-
→
Cu↓
At the Anode: Copper atoms from the anode dissolve in solution by losing two electrons.
Cu
→
Cu++ + 2e-
Hence copper atoms from anode dissolve in solution and get deposited at the cathode.
Impurities present in the anode crumbles down as anode mud.
Thus 99.99% pure copper is obtained at the cathode.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 9
SBMP/ CHEMISTRY DEPT.
Q.3) Explain the process of electrotyping.
ANS: - The process of printing letters on an article by the passage of electric current is called
as electrotyping.
Example: - electrotyping of copper letters on a wooden block. For this CuSO4 acts as an
electrolyte.
→
CuSO4
Cu++ + SO4- -
First the wooden block is covered with wax and impressions of the letters are made. To make
it a good conductor of electricity graphite powder is sprinkled on it. And it acts as cathode.
Where as pure copper plate act as anode. Both the electrodes are dipped in the electrolyte on
passing electric current.
Pure copper anode dissolves to form copper ions.
Cu
→
Cu++ + 2e-
The copper ions form accepts electrons from the cathode and gets discharged at the cathode.
Cu++ + 2e-
→
Cu↓
Thus a uniform coating of copper is obtained on the impression. Then wooden block is heated
to remove wax and washed.
Applied Chemistry/ ELECTROCHEMISTRY
Page No. 10
SBMP/ CHEMISTRY DEPT.
Chapter 3
METALS & ALLOYS
DEFINITIONS





Mineral: A mineral is defined as a naturally occurring substance
present in earth’s crust which contains metal in free or combined
state.
Ore: A mineral from which metal can be extracted economically is
known as an ore. E.g. Bauxite Al2O3.2H2O, Zinc Blende ZnS, Cuprite
CuO, Galena PbS.
Gangue or Matrix: The unwanted impurities like sand, clay, rocks, etc
associated with the ores are known as gangue or matrix.
Flux: A substance which is used to remove the gangue is known as flux.
Slag: A fusible chemical compound formed by combination of added
flux and gangue is known as slag.
QUESTIONS
1. Draw a flow chart showing the different process used for the extraction
of metals from their ores. Give the different process involved in
extraction of metals from its ores?
Applied Chemistry/ METALS and ALLOYS
Page No. 1
SBMP/ CHEMISTRY DEPT.
ORE
Gravity Separation
CRUSHING
Physical process
CONCENTRATION
Magnetic Separation
Froth Flotation
Chemical process
Calcination
Smelting
REDUCTION
Roasting
Alumino thermic process
Roasting
REFINING
Poling
Liquation
Distillation
METAL
2.
Electrolytic refining
Define concentration of ore? Name the various methods of
concentration of ore?
ANS. The process of removal of unwanted impurities from the ore is called as
concentration of ore. Different methods of concentration of ore are gravity
separation, magnetic separation, froth flotation, calcinations, roasting.
3. Explain the gravity separation process for concentration of iron ores?
ANS. Principle of the process is the difference in the densities of ore and gangue,
i.e. it is based on gravity.
Oxide ore like hematite (ore of Fe), Tinstone (ore of Sn) are concentrated by
this method.
Applied Chemistry/ METALS and ALLOYS
Page No. 2
SBMP/ CHEMISTRY DEPT.
Finely powdered ore is placed on a sloping platform and washed. The
powdered ore is allowed to flow with water.
The platform has depressions, the heavier ore particles settle in the depression.
Where as gangue or impurities are washed away.
4. Explain electromagnetic separation for concentration of ore? Explain
the process for concentration of tinstone ore?
In this process powdered ore is allowed to fall on a non magnetic leather belt
placed over an electromagnet. The magnetic impurities fall from the belt in a
heap near the magnet while the non magnetic ore falls in a separate heap.
E.g. Tinstone ore is concentrated by this method where the tin ore is non
magnetic containing iron
impurities.
Applied Chemistry/ METALS and ALLOYS
Page No. 3
SBMP/ CHEMISTRY DEPT.
5. How sulphide ores are concentrated?
Or
Explain froth flotation process?
ANS. The process is used for concentration of sulphide ores .Ore and gangue
ANS. The process is used for concentration of sulphide ores .Ore and gangue
particles have different wetting pattern with water and oil. In this process
powdered ore is mixed with water and oil. Compressed air is passed through the
mixture. Oil forms froth with air bubbles and ore particles get attached to it.
Impurities are wetted by water and sink to the bottom. Froth formed floats on the
surface and is then collected into settling basins from which concentrated ore is
obtained.
6. Define a) calcination b) roasting
ANS.
a) Calcination: Calcination is the process of heating ore strongly in absence of air
to a temperature insufficient to melt it.
b) Roasting: Roasting is the process of heating ore strongly in excess of air to a
temperature insufficient to melt it.
Applied Chemistry/ METALS and ALLOYS
Page No. 4
SBMP/ CHEMISTRY DEPT.
7. Distinguish between calcination and roasting.
CALCINATION
ROASTING
1. Ore is heated in absence of air.
1. Ore is heated in presence of air.
2. This process is for carbonate and
hydroxide ores.
2. This process is used for sulphide
ores.
3. The mass becomes more porous.
3. The mass becomes less porous.
4. It is carried out to remove volatile
impurities and moisture from the ore.
4. It is carried out to remove moisture
and oxidize the ore.
5. Doors of the furnace are closed.
5. Doors of the furnace are open.
8. Explain the smelting of hematite ore?
ANS.
In smelting, ore is mixed with coke, reducing agent and flux and heated in a blast
furnace.
Coke (carbon) converts ore into a molten metal.
Fe2O3
+
3C
Hematite
coke (carbon)
2Fe
+
Iron
3CO
Carbon monoxide
Flux removes impurities in the form of fusible mass (slag)
CaO
Flux
+
SiO 2
Gangue
Applied Chemistry/ METALS and ALLOYS
CaSiO3
Slag
Page No. 5
SBMP/ CHEMISTRY DEPT.
9. Explain Alumino Thermic process (Thermite process)
ANS.
This process is used for oxide ores. At high temperatures, aluminium acts as a
reducing agent and reduces metal oxides. Mixture of aluminium and ore is called
thermite and is heated at high temperature. Aluminium reacts with oxygen to
form aluminium oxide and reduces the metal.
Fe 2O3 + 2Al
Al2O3
+
2Fe
Cr2O3 + 2Al
Cr2O3
+
2Fe
10. Define refining. Name the methods of refining metals.
ANS.
The process of purification of metal to get extra pure metal is called refining.
The methods of refining are Poling, Liquation, Distillation, Electro refining.
Applied Chemistry/ METALS and ALLOYS
Page No. 6
SBMP/ CHEMISTRY DEPT.
Metals and Metalloids
Metals and their alloys are the backbone of all engineering projects and products.
The uses we make of metals are related to their properties:

Car bodies are made from steel, which is mostly iron, because it is a very strong material
that is easy to press into the required shape.

Electrical wiring is made from copper because it is a very good conductor of electricity.

The filament of a light bulb is made from tungsten because this metal does not melt at the
very high temperature needed to make it white hot.
Metals have their characteristic properties because of their giant structure (large atomic radii). In
a metal crystal, the atoms are in a regular arrangement and strongly bonded together. Strong
metallic bonding makes metals hard, but allows layers of atoms to slide so that the metal is
malleable. The layers of atoms also allow an electric current to pass through.
Metal structure
We can explain the properties of metals by taking a more detailed look at their structure. Metal
crystals are made up of positive metal ions surrounded by a sea of negative electrons.
Atomic structure of a metal
The strong electrostatic attraction between positive ions and negative electrons means that a lot
of energy is needed to separate these particles from the crystal lattice. This means that metals are
strong and have high melting and boiling points.
Much less energy is needed to slide one layer of positive metal ions over another layer. This
means that metals are easy to beat or press into shape.
Applied Chemistry/ METALS and ALLOYS
Page No. 7
SBMP/ CHEMISTRY DEPT.
The sea of electrons in a metal crystal is mobile. If a potential difference is applied across a piece
of metal, the electrons will move, carrying an electrical current. This means that metals are good
conductors of electricity.
Definition of properties of metals:
The description about the important mechanical properties of the metals is given below:
1. Hardness: Hardness is the ability of the metal to resist wear or abrasion and resist
penetration. For example, tungsten metal is found to be the hardest and potassium is
found to be the softest among the metals.
2. Ductility: It is the property of the metal by which it can be stretched in length without
breaking. Metals like copper, silver, gold and platinum having this property they can be
easily drawn into wires.
3. Malleability: It is the property by virtue of which a metal can be hammered into shapes
without cracking or rolled into thin sheets without tearing or breaking e. g. gold, silver,
platinum, aluminium, copper etc., are most malleable.
4. Toughness: The property of a metal to resist repeated shocks or vibrations without
breaking is called as toughness. It is a highly desirable property, of any metal. For
example, gold and silver are tough metals.
5. Brittleness: It is just opposite to toughness. It is the property of a material (like glass)
which does not permit permanent deformation without breakage. Dropping a brittle
material from a certain height on a hard floor causes it to break into pieces. Brittleness is
an undesirable property of an engineering material.
6. Tenacity: Tenacity of a metal is measured by the weight which its wire (1 sq. inch crosssection) can support.
7. Tensile strength: The strength of a metal is the ability to carry a load without breaking.
A tensile strength of a metal is its ability to resist pull without breaking.
8. Weldability: It is the process of uniting two pieces of metal by means of heat, by
bringing their ends in the molten state.
9. Machinability: It is the property due to which a material can be easily cut by cutting
tools to produce a desired shape and surface finish on its surface.
10. Casting: "The process of pouring molten metal into a mould and allowing it to solidify is
known as casting."
11. Forging: "The process of giving pre-determined shape to a piece of metal at sufficiently
high temperature when metal is in the plastic state is known as forging."
12. Extrusion: "The process by which a piece of metal is reduced in cross-section by forcing it to
flow through a die orifice under high pressure is known as extrusion process."
13. Brazing: "A method of joining metal surfaces by introducing molten non-ferrous alloy with
melting point above 400°C between them, is known as brazing."
14. Soldering: "A method of joining the metal surfaces by introducing a molten non-ferrous with
melting point below 400°C between them, is known as soldering."
Applied Chemistry/ METALS and ALLOYS
Page No. 8
SBMP/ CHEMISTRY DEPT.
Physical properties and applications of some commonly used metals and metalloids:
Iron (Fe)
Iron is the most commonly used metal in the world, and probably one the most abundant in the
earth's crust. Some of its most important properties are ductility, malleability and thermal
conductivity. It is known to be a ferromagnetic material. Iron is well known for its even-heating
property. Iron has tensile strength, which provides structural solidity to any structure.




Steel is essential in construction work and machine parts because it can withstand high
pressure and temperature.
Uniform heating quality of cast iron makes it ideal for kitchen utensils like skillet.
Metallic iron is used for making permanent and electromagnets because of its magnetic
properties.
Iron chloride is used for making dyes, pigments and paints.
Aluminum (Al)
Aluminum is abundant in the earth's crust. It has low density. It also has a thin layer of oxide on
its surface, which stops air and water getting to the metal making it corrosion resistant.





Heavy industrial and manufacturing applications, such as automobiles and aircraft
industry and in construction such as window frames, roofing etc.
Good electrical conductivity coupled with ductility and corrosion resistance makes it a
perfect choice for long-distance electricity distribution.
It is used in household items such as saucepans and cooking foils.
High reflectivity makes it ideal for mirrors, reflectors and heat resistant clothing for firefighting.
It is also used in solid rocket fuel and thermite.
Copper (Cu)
Copper is one of the earliest metals to be used for making tools and even coinage. This is
because it is ductile and easy to work with. It is a good conductor of heat and electricity. Copper
is mostly used in the form of alloys because it is too soft to be used in its pure form. Copper is
mixed with zinc to make brass and with tin to make bronze.






About 65% of copper that is produced is used for electrical applications like power
transmission, motors and in wiring and contacts for PC, TV, mobile phones and various
other electric circuitry due to its ductility and excellent electrical conductivity.
It is mostly used in piping because of its malleability.
It is used in heat exchangers and heat sinks due to its superior heat dissipation capacity.
Copper has been used in roofing since ancient times because it is waterproof and has
recently replaced lead for plumbing in houses.
It is used to make electromagnets required for locks and electric bells.
Due to its antimicrobial properties it is used in providing hygienic surfaces in hospitals.
Applied Chemistry/ METALS and ALLOYS
Page No. 9
SBMP/ CHEMISTRY DEPT.
Titanium (Ti)
Titanium is found to be stronger, durable and corrosion resistive in comparison to steel but it is
expensive and difficult to mine. It has the highest strength to weight ratio of all the metals. All
these properties, along with its light weight, make it an ideal metal for




spacecrafts and military jets
artificial hip joints
pipes in nuclear power stations
water-resistant diving watches.
Zinc (Zn)
Zinc is hard and brittle.





It is primarily used in galvanization, for example coating of iron and steel because of its
corrosion resistance.
It is also used in batteries as the negative electrode.
Zinc alloys are used in die-casting in the automobile industry.
Zinc oxide is a white pigment used in paints, plastics, rubber.
Zinc sulphide is used in making luminous dials and fluorescent lights.
Chromium (Cr)
Chromium is a lustrous, brittle, hard metal. Its colour is silver-gray and it can be highly polished.







Due to its hardness and resistance to corrosion it is mainly used in the manufacture of
stainless steel.
It is extensively used as an electroplated protective coating because of its resistance to
ordinary corrosive reagents. For example chromium plating on cars and bicycles, produces
a smooth, silver finish that is highly resistant to corrosion.
High melting point and resistance to heat makes it an ideal refractory material used in
blast furnaces, cement kilns and metal casting.
It is also known for its remarkable magnetic property. Chromium (IV) oxide is used to
produce magnetic tapes, which are used in audio tapes and cassettes.
It is used as a catalyst in dyeing and in the tanning of leather.
Salts of chromium are used for their toxic properties in preserving wood from decay and
damage caused by fungi, insects, termites, etc.
Chromium compounds are valued as pigments for their vivid colours.
Applied Chemistry/ METALS and ALLOYS
Page No. 10
SBMP/ CHEMISTRY DEPT.
Nickel (Ni)
Nickel is a hard, silvery-white metal, which is malleable and ductile. The metal can take on a
high polish and it resists tarnishing in air. It is a fair conductor of heat and electricity.

Nickel is used primarily for its alloys that are characterized by strength, ductility, and
resistance to corrosion and heat. It is mainly used for making stainless steel.

Copper-nickel alloy tubing is used in desalination plants. This alloy is also resistant to
seawater and therefore used for propeller shaft in boats.

Nickel plating is applied to other metals to provide a protective coating.

Finely divided nickel is used as a catalyst for hydrogenating vegetable oils.

Nickel is also used in rechargeable batteries, catalysts and other chemicals, coinage.
Tin (Sn)
Tin is a soft, malleable, silvery-white metal which takes a high polish. It possesses a highly
crystalline structure and is moderately ductile. Tin has a highly crystalline structure and when a
bar of tin is bent, the crystals break, producing a characteristic 'tin cry'. Two or three allotropic
forms of tin exist. When tin is cooled below 13.2°C, it slowly changes from the white form to the
gray form (has non metallic properties). Commercial tin is protected from this problem by the
addition of small amounts of bismuth or antimony. Tin is not easily oxidized and resists
corrosion because it is protected by an oxide film. Tin resists corrosion from distilled sea and
soft tap water, but it will corrode in strong acids, alkalis and acid salts.






Due to the ease with which tin mixes with most metals and low melting point it is used as
solder for joining pipes or electric circuits.
It is not toxic and corrosion resistant making it ideal coating for steel for canning food.
The very high boiling point allows it to be used as a smooth molten surface to make 'float'
glass (gives a flat surface on which to make glass).
Crystalline niobium-tin alloy is used for superconducting magnets.
Tin oxide is used for ceramics and in gas sensors (as it absorbs a gas its electrical
conductivity increases and this can be monitored).
Tin chloride (stannous chloride, SnCl2) is used as a reducing agent and mordant in dyeing
textiles.
Lead (Pb)
Lead is a bluish-white lustrous metal. It is very soft, highly malleable, ductile, and a relatively
poor conductor of electricity. It is very resistant to corrosion but tarnishes upon exposure to air to
form a dull gray coating.


Lead is mainly used in lead-acid battery (e.g. car batteries).
It is used in the glass of computer and television screens and in x-ray rooms and nuclear
reactors to protect the user from radiation.
Applied Chemistry/ METALS and ALLOYS
Page No. 11
SBMP/ CHEMISTRY DEPT.






Historically, lead was used in plumbing.
It is used to store corrosive liquids due to its corrosion resistance.
Lead oxide is used in the production of fine crystal glass.
Tetraethyl lead is used as an anti-knock agent in petrol. The use of lead in plumbing,
petrol and paints has been reduced in the past few years because of environmental
concern, as lead is a cumulative poison.
Lead is also used in cable covering, as ammunition, as electrodes, in solder and as roofing
material. Lead oxide is also used in the manufacture of fine crystal glass.
It is used as a coloring element in ceramic glazes.
Silver (Ag)
Silver is a soft, ductile, malleable, lustrous metal. It has the best electrical and thermal
conductivity of all metals. It is stable in oxygen and water, but tarnishes when exposed to sulphur
compounds in air or water to form a black sulphide layer.







Silver is a precious metal used to make jewelry, coins and cutlery.
About 30% of silver produced is used as silver nitrate in photography.
It is used in Dental alloys.
It is used in the electronics. Printed circuits are made using silver paints, and computer
keyboards use silver electrical contacts.
It is used in high-capacity silver zinc and silver cadmium long-life batteries.
Silver iodide is used in cloud seeding to produce rain artificially.
Silver chloride is used as cement for glass.
Silicon (Si)
Silicon is a hard, relatively inert metalloid. It like water expands when it freezes.







Silicon is most commonly used for in the production of electronics because of its
semiconductor property– solar panels, computer chips, electrical circuits.Silica (SiO2) is
widely used in construction.
It is a constituent of clay, concrete, brick, sand, and cement.
It is used to make glass.Silicon is an important constituent of steel.
It is important in the automotive casting industry to improve the strength of iron.
Silicones are important silicon based polymers and have many useful properties,
including use as adhesives, sealants, and insulators.
Pure crystalline silicon dioxide (quartz) resonates at a very precise frequency and is used
in high-precision clocks.
Silicon carbide (carborundum) is extremely hard and used in abrasives. It is used in
lasers.
Applied Chemistry/ METALS and ALLOYS
Page No. 12
SBMP/ CHEMISTRY DEPT.
ALLOYS
Composition, Properties & Uses of Alloys:
Sr.
No.
Alloy
Composition
Properties
Uses
1. They have low M.P. than
Cu and Zn.
1.
Brass
Cu = 60 – 90%
Zn = 40 – 10%
2. They
possess
greater
In utensils, condenser
strength, durability and
tubes,
sheets
and
machinability than pure
cartridges.
copper.
3. They are good corrosion
resistant against water.
2.
3.
4.
Bronze
Gun metal
Monel
metal
Cu = 75 – 90%
Sn = 25 – 10%
Generally harder, stronger and
tough alloys, resistant to In utensils, statues, coins
corrosion and wear, can be and bells etc.
easily casted and machined.
Cu = 88%
Sn = 10%
Zn = 2%
For making gun-barrels.
It is hard, tough and strong to
In hydraulic and boiler
resist the force of explosion. It
fittings foundry works
is resistant to corrosion by
and heavy load bearings
water and atmosphere.
etc.
Cu = 30%
Ni = 67%
Fe
Mn = 3%
1. It has bright attractive
appearance, strong, tough,
high tensile strength (5500
For making turbine blades
kg/cm2) after annealing.
and automobile engine
kitchen
sinks,
2. It is very much resistant to parts,
chemical and sea water valves, pumps, resistance
corrosion.
wires
and
transistor
capsules etc.
3. It has good mechanical
properties even at high
temperature.

Applied Chemistry/ METALS and ALLOYS
Page No. 13
SBMP/ CHEMISTRY DEPT.
Sr.
Alloy
No.
Composition Properties
Uses
1. It is Silvery White metal,
does not tarnish and can be
easily polished.
5.
Babbit
metal
Sn= 88%
Sb = 8%
Cu = 4%
2. It is rather soft material.
In
making
3. It has low coefficient of Bearings.
friction.
Engine
4. It resists wear, tin increases
compression strength.
6.
7.
8.
Duralumin
Magnalium
Alnico
Al = 95%
Cu = 4%
Mg = 0.5%
Mn = 0.5%
1. It is light, tough, highly
ductile, easily castable,
corrosion resistant and good 1. For making aeroplane,
automobile
and
conductor of heat and
locomotive parts from
electricity.
the ‘alcad’ sheets.
2. It is strong as mild steel,
though its density is 1/3rd 2. In making cables,
surgical
instrument
that of steel.
and fluorescent tube
3. Its tensile strength can be
caps.
raised by heat treatment upto
2000
kg/cm2
without 3. For making rivets,
bars, body of vehicles
affecting its ductility.
and housing cases etc.
4. It can be easily worked and
possess high machinability.
Al = 90%
Cu =10%
It is quite strong, tough and
lighter even than aluminium. It For making balance beams
can be easily worked on the and light instruments.
lathe.
Al = 20%
Ni = 20%
Co =10%
Steel= 50%
These steels have
magnetic properties.
Applied Chemistry/ METALS and ALLOYS
1. For making small
powerful
permanent
magnets
for
magneto
strong
loud speakers, radio
and T.V. sets.
2. In transformer cores,
dynamos, motors etc.
Page No. 14
SBMP/ CHEMISTRY DEPT.
Chapter 4
WATER
Q.1) Name the different sources of Natural Water.
A. The main sources of water are:
a) Rain water
b) Surface water
c) Ground water
Surface water is of three types
i) River water
ii) Sea water
iii) Lake water
Q.2) Describe the common impurities present in Natural Water.
Common impurities present in natural water are
1) Suspended impurities: water may contain suspended impurities such as clay, mud, algae, industrial
waste, organic matter etc.
2) Dissolved impurities: These are of two types:
a) Gases: gases like oxygen, carbon dioxide, oxides of nitrogen, hydrogen sulphide, and sulphur
dioxide are soluble in natural water.
b) Mineral salts: salts like the carbonates, bicarbonates, sulphate, and chlorides of calcium,
magnesium, sodium and potassium may be present in natural water.
3) Colloidal impurities: Colloidal particles are charged particles having size about 10-4cm to 10-7cm
colloidal particles of clay, fine mud, decayed leaves organic matter may be present in water.
4) Biological impurities: Microorganisms like bacteria, algae, fungi may be present in natural water.
Q.3) What is Hard Water? State the causes of hardness of water.
Water which does not produce good lather with soap readily and develops curd like substance is known
hard water.
Causes of hardness of water:
Rain absorbs Carbon dioxide from air and when it flows over the rocks containing calcium, magnesium
carbonates it combines to from bicarbonates which are more soluble in water.
H2O
+
H2CO3 +
Carbonic acid
CO2
→
H2CO3
Carbonic acid
CaCO3
Calcium Carbonate
→
Ca (HCO3)2
Calcium Bicarbonate (soluble)
Applied Chemistry/ Water & pH
Page No. 1
SBMP/ CHEMISTRY DEPT.
On the surface, chlorides & sulphates of calcium or magnesium are also present and are soluble in water.
Presence of all these salts in water makes the water hard.
Q.4) Name the chemical compounds that impart hardness to natural water.
The chemical compounds that impart hardness to water are:
Calcium Bicarbonate
Ca (HCO3)2
Magnesium Sulphate
MgSO4
Magnesium Chloride
MgCl2
Calcium Sulphate
CaSO4
Calcium Chloride
CaCl2
Q.5) Explain the types of hardness of water.
There are two types of hard water
1. Temporary hard water: Water containing bicarbonates of calcium & magnesium, which can be
made free from these salts easily by just boiling, is known as temporary hard water.
2. Permanent hard water: Water containing sulphates and chlorides of calcium and magnesium,
which cannot be made free from these salts easily (i.e. just by boiling) is known as permanent hard
water.
Q.6) Explain Degree of Hardness and state the different units by which it is measured.
Hardness of water is due to the presence of calcium or magnesium salts in it hence it is expressed in terms
of part by weight of calcium carbonate.
There are three systems to express hardness of water:
1. Degree Clark: The number of parts by weight of calcium carbonate present in 70,000 parts by
weight of water is said to be degree Clark.
1 part by weight of CaCO3
1° Clark
=
70,000 parts by weight of water
2. French degree of hardness: It is the number of parts by weight of calcium carbonate present in
1,00,000 parts by weight of water.
1 part by weight of CaCO3
1° French
=
1,00,000 parts by weight of water
3. Parts per million (ppm or mg/litre): It is expressed as the number of parts by weight of calcium
carbonate present per million parts by weight of water.
1 part by weight of CaCO3
1 ppm
=
10,00,000 parts by weight of water
Applied Chemistry/ Water & pH
Page No. 2
SBMP/ CHEMISTRY DEPT.
Q.7) Explain the disadvantage of using hard water in
a) Paper industry b) Dyeing industry c) Textile industry d) Sugar industry
e) Domestic industry
a) Paper industry: If hard water is used for paper manufacturing then Ca2+ & Mg2+ ions present react
with the resins added during the manufacturing of paper and hence the paper manufactured does
not have the desired smoothness and glossiness.
Moreover due to the presence of iron and Mg impurities in water the whiteness or colour of paper
may be affected.
b) Dyeing industry: Dye is colouring matter used in textile and plastic industry. The dissolved salts
of Ca, Mg & Fe my react with dyes to form undesirable precipitates due to which improper shades
of dyes are formed. Moreover if iron is present in water it produces spot or yellow stains on clothes
hence hard water should not be used in dyeing industry.
c) Textile industry: If hard water is used in textile industry then large quantity of soap will be wasted
while washing the yarn Because hard water easily does not produce lather with soap indeed it forms
undesirable precipitate of fatty acids this precipitate may adhere to the fabrics while dyeing and
hence exact shade may not be obtained. If Fe or Mg salt are present it causes stains on fabrics.
d) Sugar industry: If water used in sugar industry contains impurities like sulphates, alkali carbonate,
nitrate and bacteria then the sugar may not crystallite well. And it may be deliquescent.
e) Domestic Use: Water is largely used for domestic purpose. i.e. washing, bathing, cooking,
drinking.
Washing: If hard water is used for washing, it does not produce lather with soap but produces
sticky curdy precipitate. Hence large quantity of soap is wasted.
Cooking: Ca, Mg salts preset in hard water increase the boiling point of water hence more time
and fuel is consumed for cooking certain foods such as pulses, beans & peas.
Bathing: Since lather is not formed by hard water cleansing capacity of soap is decreased. More
over the fine particles of precipitates of Ca & Mg get adsorbed to the skin making it dry and dark.
Drinking: If hard water is used for drinking purpose it causes bad effects on our digestive system.
By using hard water there are possibilities of forming calcium oxalate crystals in the urinary tract.
Q.8) Explain the disadvantages of using hard water in steam generation in boilers.
Most of the water used in industry & power houses is in the form of steam and for steam generation boilers
are used. If hard water is used directly in boilers certain problems are developed such as:
1) Scale
2) Corrosion 3) Priming & foming
4) Caustic embrittlement.
1) Scales & sludge formation: In boiler water is evaporated continuously and the concentration of
the dissolved salts in it increases. These salts form precipitate on the inner walls of the boilers in
the form of sludge & scales.
2) Boiler corrosion: Boiler corrosion is decay of boiler material by the chemical or electrochemical
attack by its environment
Corrosion in boilers takes place due to the following reasons:
Applied Chemistry/ Water & pH
Page No. 3
SBMP/ CHEMISTRY DEPT.
a) Dissolved oxygen in water
b) Dissolve carbon dioxide
c) Acids formed due to dissolved salts of Mg
3) Priming and forming: When a boiler is steaming some particles of liquid water are carried along
with the steam, this process of wet steam formation is said to be priming.
Foming is production of persistent from or bubble in boilers which do not break easily is called as
sludge.
4) Caustic embrittlement: When highly alkaline water is used in boilers it causes corrosion known as
caustic embrittlement.
Q.9) Define Scale and Sludge. Explain its formation in boilers.
Scales: These are hard precipitates which stick firmly to the inner wall of the boiler e.g. Coating CaSO4
Sludge: These are soft, loose and slimy precipitate formed within the boiler e.g. Coating CaCO3 &
MgCO3.
Formation of scales and sludge:
In boiler water is evaporated continuously and the concentration of dissolved salts in it increase these salt
stick to the wall of the boiler.
If the precipitate is loose and slimy it is called sludge and if it is hard adherent it is called scale.
Q.10) Explain priming and foaming in boilers.
During steam generation in boilers some particles of liquid water in boilers some are carried along with
steam, this process of wet steam formation is called priming.
Priming is caused presence of large amount of dissolve solids , high steam velocities ,sudden boiling ,
improper boiler design or sudden increase in steam production rate.
Foaming is the production of persistent foam or bubbles in boilers which do not break easily it is due to
presence of substance like oil.
Q.11) Explain the process of Caustic Embrittlement in boilers.
When highly alkaline water is used in boiler, it causes corrosion known as caustic embrittlement.
In lime soda process of purification of water when Na2Co3 is taken in excess. It remains in water. When
this water is used in boilers it decomposes to form NaOH and CO2. This NaOH formed flows into minute
cracks in the inner walls of the boiler and reacts with the iron of the boiler to form sodium ferroate. Thus
weakening the boiler plate causing even failure of the boiler This is called caustic embrittlement.
Applied Chemistry/ Water & pH
Page No. 4
SBMP/ CHEMISTRY DEPT.
Q.12) Distinguish between Scales and Sludges.
Ans.
Sr.
No.
1
2
3
4
Scales
Sludges
They form an adherent coating within the
boiler which cannot be removed even by
mechanical means.
They are harder and more permeable.
They are bad conductor of heat.
They are formed throughout the metal surface
in contact with water.
They form a slimy or less adherent coating in the
boiler which can be removed even by mechanical
means.
They are soft and less permeable.
They are poor conductor of heat.
They are formed at comparatively cooler portions
of the boiler.
Q.13) What are the disadvantages of Scales and Sludges?
Ans. Following are disadvantages of Scales and Sludges:
5) Wastage of fuel: Scales are hard and bad conductor of heat, hence do not allow ready transfer of
heat to the boilers. Therefore more heat has to be applied and more fuel is consumed.
6) Lowering safety of boiler: Due to scale formation, boiler is overheated which makes the boiler
material softer and weaker and causes distortion of boiler tube.
7) Decrease in efficiency: Scales deposit in the valves and condensers of boiler and chokes them
partially hence efficiency of the boiler decreases.
8) Danger of Explosion: When thick scales crack due to uneven expansion of scale and boiler
material, water comes in contact with overheated iron plates leading to formation of large amount
of steam suddenly. Hence high pressure is developed causing explosion of boilers.
Q.14) What are the disadvantages of Priming and Foaming?
Ans. Following are disadvantages of Priming and Foaming:
1) Actual height of water in boiler is not judged.
2) To adjust steam pressure in boilers, more heat is required hence efficiency decreases.
3) Water and dissolved salts may get deposited on machinery parts.
Applied Chemistry/ Water & pH
Page No. 5
SBMP/ CHEMISTRY DEPT.
Chapter 5a
CORROSION
Q.1) Define Corrosion
Ans. Any process of decay or destruction of a metal due to the action of surrounding medium is called
corrosion.
Q.2) Name the types of corrosion.
Ans. There are two types of corrosiona. Atmospheric Corrosion
b. Immersed Corrosion
Q.3) Explain the magnitude of corrosion problem.
Ans. Corrosion is a slow process but the losses resulting from it are uneconomical.
The damage or loss due to corrosion cannot be measured by the cost of the metal alone but also the high
cost of fabrication and extraction.
Moreover it causes considerable reduction in life of machinery or defects in machinery which may cause
causalities or injuries to workers.
Due to weakening of metallic structures like bridges there can be loss of life as well.
Hence Corrosion is a major problem today.
Q.4) Define Atmospheric Corrosion and state its types.
Ans. Atmospheric corrosion: Corrosion that occurs when metals come in direct contact with atmospheric gases
and moisture.
Atmospheric corrosion is of two typesI. Corrosion due to oxygen
II. Corrosion due to other gases
Q.5) Name the different types of oxide films formed.
Ans. Different types of oxide films formed areI.
Stable Film- Stable film consists of fine granules on the surface of the metal and it adheres to the
surface.
It is of two typesa. Porous Stable Film- This film formed does not cover the surface of the metal completely due to
which oxygen can reach the next layer of the metal and corrosion takes place.
Hence porous oxide film is non-protective film.
b. Non Porous Stable Film- This film covers the surface of the metal completely hence prevents
the metal from further corrosion. E.g., Aluminium forms non porous oxide film.
Hence non porous oxide film protective film.
II.
Unstable Film- When the oxide film is unstable it decomposes back into metal and oxygen as soon as it
is formed. Hence corrosion is not possible.
Noble metals like gold, silver and platinum form such oxide films.
III.
Volatile Film- The oxide film vaporizes as soon as it is formed. Hence a fresh metal surface is exposed
to the atmosphere and corrosion continues. E.g. Molybdenum oxide.
Applied Chemistry/ CORROSION
Page No. 1
SBMP/ CHEMISTRY DEPT.
Q.6) Explain the mechanism of atmospheric corrosion.
Ans. Mechanism of oxide film formationMetal atoms lose electrons and undergo oxidation whereas atmospheric oxygen accepts electrons and
undergoes reduction.
M 
M++ + 2eLoss of electrons
Metal ion
O + 2e-  O- Gain of electrons
M + O  M++ + O- -  MO
Thus oxides of metals are formed.
Q.7) Explain the factors affecting atmospheric corrosion.
Ans. Factors affecting corrosion are
I.
Impurities in the atmosphere: Air in the industrial areas contain traces of carbon dioxide, hydrogen
sulphide, sulphur dioxide gases and vapours of HCl, H2SO4, etc.
Presence of such acidic impurities increases the rate of corrosion.
II.
Moisture in the atmosphere: rate of corrosion increases in presence of moisture in atmosphere, i.e.,
highly humid atmosphere.
Q.8) Define Immersed Corrosion.
Ans. The corrosion that takes place through ionic reaction in presence of moisture or solution as conducting
medium when two dissimilar metals are in contact with each other is called electrochemical corrosion.
Q.9) Explain galvanic cell action of immersed corrosion.
Ans. When two dissimilar metals are electrically connected and dipped in electrolyte solution a galvanic cell is
formed
The principle of it is explained by considering Daniel cell.
Daniel Cell consists of Zn and Cu plates dipped in salt solution of Zn and Cu respectively.
The Solutions are separated by a porous partition. The plates are connected by a metallic conductor. An
e.m.f. is developed due to the redox reaction taking place.
Zn metal being more active than Cu undergoes oxidation to form Zn++ ions and comes into solution.
Zn  Zn++ + 2eCopper ions from copper salt solution undergoes reduction and gets deposited as copper metal.
Cu++ + 2e-  Cu↓
Thus Zn anode gets dissolved and corroded while copper gets deposited.
Diagram
Applied Chemistry/ CORROSION
Page No. 2
SBMP/ CHEMISTRY DEPT.
Q.10) Define Electrode Potential.
Ans. Electrode potential: When a metal rod is dipped in its salt solution, oxidation and reduction reaction take
place and an electrical double layer is formed and a potential is developed at the junction of the electrode
and the solution called electrode potential.
Q.11) Explain concentration cell action method of immersed corrosion.
Ans. The concentration cells are set up when a metal is surrounded by aqueous medium with difference of ion
concentration.
Concentration cells are of two typesa. Metal ion concentration cell- This cell is formed when the same metal piece is immersed in two
electrolytic solutions of same electrolyte having different concentrations.
The portion of the metal in dilute solution becomes anode and gets corroded and goes into
solution while the other portion of the metal which is in concentrated solution becomes cathode
and is protected.
b. Differential aeration/ Oxygen concentration cell- This cell is formed when different areas of
same metallic surface are exposed to varying oxygen concentrations.
Certain part of moist metal oxide coated or covered with sand or other impurities are less
exposed to air, i.e., less oxygenated than those part of the metal which are not covered.
The less oxygenated part becomes anode while more exposed or oxygenated part becomes
cathode and the following reaction takes place at the cathode2H2O + O2 + 4e-  4OHDiagram
This cathode reaction consumes electrons and therefore more electrons must be supplied by the adjacent
areas which are less oxygenated hence they serve as anode and undergo oxidation to form ions.
Hence area with less concentration of oxygen gets corroded.
Q.12) Explain evolution of Hydrogen mechanism of electrochemical corrosion.
Ans. This type of corrosion occurs in acidic environment like industrial waste, solutions like HCl etc.
E.g. A steel tank containing acidic medium and a small piece of copper in contact with the steel. The
portion of the steel tank in contact with copper is corroded most with evolution of hydrogen gas
At Anode:
Fe  Fe++ + 2eThese electrons flow through metal from anode to cathode. At cathode H+ ions are reduced and
eliminated as hydrogen gas.
At Cathode: 2H+ + 2e-  H2
Net Reaction:
Applied Chemistry/ CORROSION
Fe + 2H+  Fe++ + H2↑
Page No. 3
SBMP/ CHEMISTRY DEPT.
Q.13) Explain absorption of oxygen mechanism of immersed corrosion.
Ans.
Diagram
Rusting of iron in neutral solution of electrolyte in presence of atmosphere oxygen is an example of this
type of corrosion.
The surface of iron is usually coated with a thin film of iron oxide; and if the film develops some cracks
anode areas are created on the surface while the coated metal parts act as cathode.
At anodic areas metal dissolve as Fe++ ion with the liberation of electrons:
Fe  Fe++ + 2eThe liberated electrons flow from anodic to cathodic areas through the metal and react with the dissolved
oxygen in the water drop
2H2O + O2 + 4e-  4OHThe Fe ions at anode and OH- ions at cathode diffuse and form ferrous hydroxide precipitate.
Fe++ + OH- 
Fe(OH)2
Q.14) Explain the factors affecting immersed corrosion.
Ans.
A. Portion of metal in electrochemical series:
Metals at higher position in electrochemical series undergo corrosion faster than those at lower
position.
B. pH value:
Rate of pH value of the surrounding is low rate of corrosion is more. In acidic medium rate of corrosion
is high.
Applied Chemistry/ CORROSION
Page No. 4
SBMP/ CHEMISTRY DEPT.
C. Solubility of corrosion products:
If the oxide film formed due to corrosion on metal surface is soluble, it will be removed and hence next
layer of the metal is exposed to corrosion. If the film formed is insoluble, then it remains on the surface
of the metal & resists further corrosion.
D. Physical difference of the metallic surface:
It is observed that uneven surfaces enhance corrosion rate of metal. In this case troughs become anodes
(less oxygenated area) and crests become cathode (more oxygenated area) hence creating a potential
difference because crest and troughs do not have same contact with air.
E. Differential aeration:
When one part of the metal is exposed to different air concentration than other, the less oxygenated part
becomes anode and gets corroded.
PROTECTION OF THE METALS FROM CORROSION
Q.15) List the different methods used for the prevention of corrosion?
Answer: Four preventive measures to prevent the metal are
(I) Modification of the environment
Removal of corrosion stimulates
Use of corrosion inhibitors
(II)Modification of properties of the metal
Alloying
Annealing
Refining
(III)Cathodic Protection
Using sacrificial anode
Using impressed current
(IV)Use of Protective coatings
Organic protective coatings
Inorganic protective coatings
Q.16) Explain how modification of the environment can prevent corrosion?
Answer: Modification of the environment means changes in the environment to prevent corrosion. It includes two
methods
a) Removal of corrosion stimulants.
In this method the corrosion causing agent is removed or deactivated to prevent corrosion.
E.g. To prevent corrosion due to oxygen, dissolved oxygen from water is removed or demarcation is done or
reducing substance is added.
To prevent corrosion by acids they are neutralized.
Applied Chemistry/ CORROSION
Page No. 5
SBMP/ CHEMISTRY DEPT.
Use of corrosion inhibitors are organic or inorganic substances which when added to the environment from a film
i.e. physical barrier between the metal and the medium. E.g. Organic amines, cyanides, etc.
There are 3 types of corrosion inhibitors (a) Anodic inhibitors (b) Cathode inhibitors (c) Vapour phase inhibitors.
Q.17) Explain how modification of properties of the metal prevent corrosion?
Answer: Properties of the metal can be modified to reduce corrosion.
Alloying: The addition of alloying elements increases resistance to corrosion.
E.g. Addition of Cr, Ni, and Mo makes the steel corrosion resistant.
Refining: Purification of the metal reduces the rate of corrosion.
Annealing: It is the heat treatment given to metals to remove residual stress.
Q.18) State the principle of cathodic protection method to prevent corrosion?
Answer: The principle of cathodic protection method is the metal to be protected is forced to behave as cathode. It
is carried in two ways (a) Using sacrificial anode (b) Using impressed current.
Q.19) Describe cathodic protection using sacrificial anode?
Answer: The metal to be protected is connected to anode metal (more active) by an insulating wire.
More active metal like Zn, Mg and Al acts as anode & gets corroded hence known as sacrificial anode. This
method is applicable to protect buried pipelines, buried cables, hot water tanks.
Q.20) Describe cathodic protection using impressed current?
Answer: In this method an impressed current is applied in opposite direction to nullify the corrosion current &
convert the corroding metal from anode to cathode. The impressed current is derived from a DC source & given to
an insoluble anode like graphite and the negative terminal is connected to the pipeline to be protected. This method
is useful for large structures & long term operation and is applicable to buried water or gas pipelines, water tanks,
etc.
Q.21) Give reasons underground iron connected to magnesium bars.
Answer: Magnesium is more active than iron hence in presence of moisture as conducting medium, magnesium
becomes anodic & iron becomes cathodic thus magnesium undergoes corrosion & iron pipelines are protected.
Protective Coatings: To decrease corrosion metal surface can be coated. There are two types of coatings Organic
Protective Coatings & Inorganic Protective Coatings.
Applied Chemistry/ CORROSION
Page No. 6
SBMP/ CHEMISTRY DEPT.
Q.22) Write a note on Inorganic Protective Coatings
Answer: (a) Formation of oxide film: some metals like Al, Sn and Cr form insoluble oxide thus protects the metal
from corrosion.
(b) Phosphate Coating: Iron when dipped in phosphoric acid forms insoluble ferric phosphate which adheres to the
metal surface & prevents corrosion.
(c) Metal Coating: Coating one metal on the other reduces the rate of corrosion. It can be done in two ways (I)
Coating of less active metal (II) Coating of more active metal.
(d) Coating of Less active metal: Less active metal is quite inert hence provides mechanical protection to the base
metal.
E.g. Coating of tin on iron to prevent iron from corrosion.
(e) Coating of More active metal: More active metals like Zn protects the base metal from corrosion as it acts as
anode & the base metal becomes cathode thus the base metal is prevented.
E.g. Coating of Zinc on iron to prevent iron from corrosion.
METHODS OF APPLYING METAL COATINGS
Q.23) Explain Galvanizing with a suitable diagram?
Answer: Galvanizing is the process of coating iron or steel sheet with thin coat of zinc to prevent corrosion.
Diagram:
The iron or steel to be coated is first cleaned with dilute H2SO4 to remove impurities.
It is then dipped in a bath of zinc ammonium chloride & then dried.
The sheet is then dipped in a bath containing molten zinc at a temperature of 4250C to 4600C for coating. The
surface of the bath is covered with ammonium chloride to prevent oxidation.
The sheet is then passed through hot rollers to make the coating uniform and to remove excess zinc. Further the
sheet is annealed & then cooled.
Applied Chemistry/ CORROSION
Page No. 7
SBMP/ CHEMISTRY DEPT.
Advantages: Zinc prevents the base metal even if the coating is improper or damaged as Zn acts as anode (more
active) and iron becomes cathodic.
Smooth and high quality coating is obtained. High resistance to mechanical wear & damage.
Disadvantages: Galvanized utensils are not used for storing food stuffs.
Applications: Widely used for protecting iron exposed to atmosphere like roofing sheets, pipes, etc.
Q.24) Give Reasons:
(a) Galvanized utensils are not used for storing food stuffs:
OR Zinc coated utensils are not used but tin coated utensils are used for storing food stuffs.
Answer: Zinc of galvanized utensils dissolves in dilute acids of food and forms highly toxic zinc compounds.
Hence galvanized utensils are not used for storing food stuffs.
(b) Iron corrodes faster than Aluminium even though Aluminium is more active than iron:
Answer: Aluminium undergoes atmospheric corrosion to form a non porous oxide film of Al2O3 which is
protective and prevents further corrosion. Thus iron corrodes faster than aluminium.
(c) Iron does not rust if zinc coating is broken in galvanized iron pipe:
Answer: Zinc is more electro positive (active) than iron so zinc coating gets as anode while iron pipe acts as
cathode. Hence when the coating breaks zinc corrodes and iron being cathodic is prevented.
(d) Copper equipment should not possess small sheet bolts:
Answer: Iron is more active than copper hence becomes anodic and corrodes while copper is comparatively very
low in e.c.s hence is highly cathodic since anodic areas are small it gets corroded completely. Hence action of bolt
in the equipment is finished.
Q.25) Explain tinning process of coating the metal?
Answer: The process of coating iron and steel products with a thin coat of tin by dipping it in molten tin to prevent
it from corrosion is called tinning.
Diag.
Applied Chemistry/ CORROSION
Page No. 8
SBMP/ CHEMISTRY DEPT.
The iron or steel sheet is first cleaned with dilute H2SO4 to remove oxide layer, rust and impurities. The iron sheet
is then passed through ZnCl2 flux layer which helps the molten metal adhere to the metal sheet.
Then the sheet is passed through molten tin where by the metal gets coated.
Then the sheet is passed through palm oil to prevent the tin coated surface from oxidation. Further the iron or steel
sheet is then passed through rollers to remove any excess tin and produce a thin uniform film.
Applications: Tinned copper utensils are used as cooking utensils and storing utensils.
Copper wire is tinned to facilitate soldering.
Advantages: Tin is less active hence more resistant to the chemical attack and protects the base metal. Tinned
containers can be used for storing food stuffs.
Disadvantages: In case tin coating formed does not cover the surface completely or cracks develop on the coated
layer more rapid corrosion takes place because iron is higher in the electrochemical series than tin, hence iron
becomes anodic and tin becomes cathodic. Thus iron gets corroded.
Q.26) Distinguish between galvanizing and tinning.
GALVANISING
TINNING
It is the process of coating iron or steel Sheet with a thin It is the process of coating iron or steel sheet with a thin
coat of Sn to prevent it from corrosion.
coat of Zn to prevent it from corrosion.
In this process Zn protects iron as it is more electro
positive than iron and hence does not allow iron to pass
into solution.
In galvanizing, Zn protects the base metal even if the
coating is broken.
Galvanised utensils are not used for storing food stuffs.
In this process Sn protects iron as it is less electro
positive than iron and therefore it is more resistant to
chemical attack.
In tinning Sn protects the metal till the coating is
perfect.
Tinned utensils can be used for storing food stuffs.
Q.27) Explain metal spraying method of coating a metal?
In this method molten metal is sprayed on the surface of base metal by a spraying gun. The spraying gun consists
of a duct of compressed air and fitted with oxyacetylene flame.
Diag.
Applied Chemistry/ CORROSION
Page No. 9
SBMP/ CHEMISTRY DEPT.
The metal to be coated is fed in the form of wire .The metal is melted due to the oxyacetylene flame and the
molten metal is blown out into spray by means of compressed air. The spray can be directed to the surface which is
to be coated and the metal sprayed adheres to the surfaces of the metal and protects the metal.
Applications and advantages
Spray coats may be given to any surface even fabricated structures. It can be applied to non-metallic surfaces like
wood, plastic and glass.
Worn out machine parts can be reclaimed by metal spraying.
Thickness of coating can be controlled.
Q.28)Explain cementation or diffusion coating and state its type.
Cementation means heating the base metal with powdered coating metal in an inert atmosphere resulting in
diffusion of coating metal into base metal forming an alloy layer on the surface of the base metal to prevent it from
corrosion.
Types of cementation:- 1.sherardizing :It is a process of coating odd shaped iron articles with a thin layer of zinc
to protect them from corrosion.
2.Colorising :In this process iron articles are heated in a tightly packed drum with a mixture of
Al powder and Al2O3 with traces of NH4Cl in hydrogen atmosphere.
3.Chromising:It is carried out by heating a mixture of Cr powder and AlO with the iron articles at about 13001400 C for 3-4 hours.
Q.29) Explain the process of sherardizing?
Sherardizing is the process of coating off shaped iron articles with a thin layer of Zn to protect them from
corrosion.
In this process iron articles like nails, bolts, nuts etc are covered with Zn dust and ZnO powder and placed in a
steel drum equipped with electrical heating arrangement to raise the temperature to 4000C.It is rotated using a
motor.
Due to rotation and high temperature Zn diffuses into the top layer of iron and a Zn-Fe alloy layer is formed at the
surface thus preventing corrosion.
Diag.
Applied Chemistry/ CORROSION
Page No. 10
SBMP/ CHEMISTRY DEPT.
Applications of sherardizing:
Sherardizing is used for protecting small steel parts and there is very little change in dimensions of the articles.
Q.30) Distinguish between galvanising and sherardizing
GALVANISING
SHERADIZING
It is the process of coating iron or steel sheet with thin It is the process of coating small iron or steel article by
alloying at the surface of base metal.
coat of Zn by hot dipping.
The process is carried out in large tanks.
The process is carried out in rotating closed drum like
furnace.
In this process a layer of Zn-Fe is formed on which the In this process Zn gets diffused and a Fe-Zn alloy is
layer of zinc sticks.
formed.
This is carried out for iron sheets exposed to This is carried out for iron or steel articles like bolts,
atmosphere.
nails etc.
Q.31) Write a note on electroplating? State its application
Electroplating is the process of coating superior metal on the base metal with the help of electric current. Purpose
of electroplating is decoration and protection. Process the article to be electroplated is cleaned and made cathode.
Anode is pure metal rod whose coating is desired on the article.
Electrolyte is the solution of salt of metal whose coating is desired.
When current is passed metal ions from solution deposit on the cathode and hence anode gets dissolved in the form
of ions.
Q.32) Explain metal cladding process of protecting the metal from corrosion .
Metal cladding involves bonding firmly and permanently a dense homogeneous layer of coating metal to the base
metal on one or both sides.
In this process base metal is sandwiched between two sheets of coating metal and passed through heavy rollers at
high temperature and pressure.
Diag.
Applications: Al clad sheets are used in aircraft industry as cladding improves corrosion resistance. Cu clad steel
is corrosion resistant and has high electrical conductivity.
Advantages: Cladding metal protects to base metal.
A combination of properties of cladded metal and cladding metal may be obtained by this process.
Disadvantages: It can be done only for plain surfaces. Its cladding is not perfect; corrosion may start in presence of
moisture.
Applied Chemistry/ CORROSION
Page No. 11
SBMP/ CHEMISTRY DEPT.
Chapter 5b: PROTECTIVE COATINGS
INTRODUCTION:
"Paint is a mechanical dispersion mixture of one or more pigments in a vehicle."
The ‘vehicle’ is a liquid consisting of non-volatile film forming material, drying oil
and a highly volatile solvent, ' thinner '. When a paint is applied to a metal surface
(usually by brushing or spraying) the thinner evaporates, while the drying oil slowly
oxidises forming a dry pigmented film. To accelerate the drying process of oil small
amount of catalysts (called driers) are also added to the paint.
PURPOSES OF APPLYING PAINT:
Paints are generally used by builders/ engineers for covering the surfaces of
buildings and engineering materials such as wood, iron etc. The main purposes of
applying paint are as follows:
1.
2.
3.
4.
5.
Paint protects iron and wood from wear and tear.
Paint protects wood from different types of insects, fungus and moisture.
Paint protects iron from rusting and corrosion.
The painted surface reflects heat and light nicely.
The painted surface provides smooth and beautiful appearance.
CHARACTERISTICS OF A GOOD PAINT:
A good paint should possess the following characteristics:
1. It should be fluid enough to be spread easily over the surface to be protected.
2. It should possess high covering power.
3. It should have brushing characteristics. Brushes may be made according to the
type of paint to be applied.
4. It should form a quite tough uniform, adherent and durable film.
5. It should protect the painted surface from corrosion effects of the environment.
6. Its film should not get cracked on drying.
7. Its film should be washable.
8. Its film should be glossy.
PRINCIPAL CONSTITUENTS OF PAINT:
The important constituents of a paint are:
(1) Pigments (2) Vehicle or medium (drying oils) (3) Thinners (4) Driers (5)
Fillers or extenders and (6) Plasticizers.
Applied Chemistry/ Protective Coatings
Page No. 1
SBMP/ CHEMISTRY DEPT.
(1) Pigments: "Pigment is a solid substance, which forms a paint when mixed
with drying oil." It is the principal constituent forming the body of paint.
Types of pigments:
(a) White pigments: White lead [2PbCO3.Pb(OH)2], zinc oxide (ZnO), lithopone
(BaSO4 + ZnS), titanium oxide (TiO2) etc.
(b)
Coloured pigments:
(i) Red - Red lead, ferric oxide, chrome red etc.
(ii) Green - Chromium oxide (Cr 2O3)
(iii) Blue - Prussian blue Fe 4[Fe(CN) 6 ]3 , ultramarine blue (sodium
aluminium silicate + sulphide), cobalt blue (70% Al 2O3 + 30%
Co2O4).
(iv) Black - Carbon black, lamp black.
(v) Brown - Brown umber.
Characteristics of good pigments: Good pigments should be (i) Cheap, (ii)
Opaque (iii) chemically inert, (iv) non-toxic (v) freely mixable with filmforming constituents of the oil.
Functions of pigments: The functions of pigment in paint are to:
1. provide opacity and colour to the paint film.
2. give an aesthetical appeal (i.e., pleasing to look at) to the paint film.
3. give strength to the film.
4. give protection to the paint film by reflecting harmful ultraviolet light.
5. provide resistance to paint film against abrasion or wear.
6. improve the impermeability of paint film to moisture.
7. increase weather-resistance of the film.
(2) Vehicle (or medium or drying oil): "These are the film-forming constituents
of the paint.” In oil paints, the vehicle, or medium includes of drying oils
such as linseed oil, dehydrated castor oil and semi-drying oils such as
soyabean oil, fish oil etc. The semi-drying oils are slow-drying and hence are
used only admixture with drying oils.
Applied Chemistry/ Protective Coatings
Page No. 2
SBMP/ CHEMISTRY DEPT.
Functions of vehicle or medium: Drying oils supply paint film:
1. mainly film forming constituents.
2. toughness
3. adhesion
4. durability and water proofness
5. protective film by evaporation or by oxidation and polymerisation of the
unsaturated constituents of the oil.
(3) Thinners: "These are the volatile liquid substances which evaporate easily
after application of paint." Thinners are added to the paints to reduce the
viscosity (consistency) of the paint, so they can be easily applied to the metal
surface. Common thinners used in paint are:
(i)
Aliphatic hydrocarbons: mineral spirits, napthas and other petroleum
fractions. (e.g. kerosene).
(ii) Aromatic hydrocarbons: Benzene,
naphthalene, turpentine and dipentene.
tuluol,
xylol,
methylated
Functions of Thinner: The important functions of thinner are as follows:
1. They suspend pigments.
2. They dissolve film-forming materials.
3. They thin (or reduce viscosity of) the concentrated paints for proper
handling and to impart better covering power.
4. They help the drying of film by evaporation.
(4) Driers: "These are oxygen carrier catalysts." They accelerate the drying of
oil-film through oxidation, polymerisation and condensation. The commonly
used driers are heavy metallic soaps such as napthenates, linoleates, resinates
and tungstates of heavy metals Co, Mn, Pb and Zn.
Types of Driers:
(i)
Cobalt substances are the most efficient of all and are 'surface-driers'.
(ii)
Lead substances are ‘bottom driers’.
Applied Chemistry/ Protective Coatings
Page No. 3
SBMP/ CHEMISTRY DEPT.
(iii) Manganese substances are 'thorough driers'.
Too much of a drier tends to produce hard and brittle paint films.
Functions of Driers: The functions of driers are as follows:
1. They improve the drying quality of oil-film.
2. They act as oxygen carrier catalysts.
3. They accelerate the drying of oil film by oxidation, polymerisation and
condensation.
(5) Fillers or Extenders: These are the inert materials which improve the
properties of the paint although they have low opacity. Commonly used
extenders are barytes (BaSO 4), CaCO3, CaSO4, talc, asbestos, gypsum, clay,
chalk, silica, magnesium silicate (MgSiO3), slate powder etc.
Functions of Extenders: The functions of extenders are as follows:
1. They reduce the cost of paint.
2. They increase the durability of paint.
3. They help to reduce the cracking of dry paint and keep the pigments in
suspension.
4. They serve to fill the voids in the film.
5. They increase random arrangement of pigment particles.
6. They act as carriers for the pigment colour.
(6) Plasticizers: Plasticizers are substances used in paints (i) to give elasticity
to the film, (ii) to prevent cracking of the film. Plasticizers in common use
are triphenyl phosphate, tricresyl phosphate, diamyl phthalate, tributyl
phthalate, and dibutyl tartarate.
VARNISHES:
"Varnish is a homogeneous colloidal dispersion, solution of natural or synthetic
resins in oils or thinners or both."
It is used as a protective and decorative coating of suitable surfaces and it dries up
by evaporation, oxidation and polymerisation of its constituents, leaving behind a
hard, transparent, glossy, lustrous and durable film.
Applied Chemistry/ Protective Coatings
Page No. 4
SBMP/ CHEMISTRY DEPT.
Types of varnishes:
1. Oil varnishes (or Oleoresinous varnishes): These are homogeneous solutions of
one or more natural or synthetic resins in a drying oil and volatile solvent to which
some driers are added. This type of varnish dries up slowly (drying period about
24 hours) by the evaporation of volatile solvent followed by oxidation and
polymerisation of the drying oil. But the film produced is hard, quite lustrous and
durable. e.g. Copal varnish (prepared by dissolving copal in linseed oil and
turpentine). They are used for interior as well as exterior works.
2. Spirit varnishes: These varnishes are prepared by dissolving resin completely in
volatile solvent like methylated spirit. In spirit varnishes instead of oil, spirit is
used. Spirit varnishes dries up quite rapidly, but leaves behind a film which is
brittle and so, has a tendency to crack or peal-off very soon. To avoid this some
plasticizers are added. Moreover, the film is easily affected by weathering e.g., spirit
varnishes are made by dissolving shellac (resin) in the spirit or alcohol.
CHARACTERISTICS OF GOOD VARNISH:
A good varnish should possess the following characteristics:
1. It should be soft and tender.
2. It should dry very quickly.
3. On drying, the film of the varnish should be glossy, shining and aesthetically
appealing.
4. It should give a hard, tough, durable wear and tear resistant film.
5. It should be able to adopt itself to the expansion or contraction of coated
material such as wood, because of variation of temperature.
6. Its film should be elastic, which does not crack or peel off or shrink on drying.
7. Its film should not fade or change of colour on exposure to atmospheric
weather.
Uses of varnishes: Varnishes are used:
1. for the protection of articles against atmospheric corrosion.
2. as a brightening coat to painted surface.
3. for improving the appearance and intensifying the ornamental grains of
wooden surfaces.
Applied Chemistry/ Protective Coatings
Page No. 5
SBMP/ CHEMISTRY DEPT.
DISTINCTION BETWEEN PAINTS and VARNISHES:
Sr.
No.
1.
2.
3.
4.
5.
6.
Paints
Varnishes
Paint is a mechanical dispersion
mixture of one or more pigments in
a vehicle.
Paint contains pigments.
Paint obscure (i.e. hide) the surface
on which it is applied.
Paint produces non-transparent
(opaque) film.
In paint, instead of oil, the resins
cannot be used.
Painted surface reflects heat and
light nicely.
Varnish is a homogeneous colloidal
solution of resins in oil or thinner or
both.
Varnish do not contain pigments.
Varnish do not obscure the surface
on which it is applied.
It produces transparent film.
Applied Chemistry/ Protective Coatings
In varnish, instead of oil, the resins
can used.
Varnished surfaces do not reflect
heat and light.
Page No. 6
SBMP/ CHEMISTRY DEPT.
Chapter 6: LUBRICANTS
INTRODUCTION:
In all types of machines, the surface of moving or sliding parts rub against
each other. Due to rubbing of one part against the other, a resistance is
offered to their movement. This resistance is known as 'friction.' The friction
causes a lot of wear and tear of surfaces of the moving parts. Consequently,
such parts are to be replaced periodically.
Due to friction, a large amount of heat energy is dissipated, thereby causing
loss in the efficiency of machine. Moreover, the moving parts get heated up,
and deformed (change their shape). The ill-effects of frictional resistance can
be minimised by using a suitable substance, which forms a thin layer in
between the moving parts.
“Any substance int roduced between two moving or sliding surfaces to
reduce the frictional resistance between them is known as a lubricant. ” The
lub ric ating la ye r c ar ries away the heat developed and keeps apart the
two surfaces from coming in contact and thus protects the machine parts from
wear and tear.
“The process of reducing frictional resistance between moving or sliding
surfaces by the introduction of lubricants in between them, is called
lubrication.”
FUNCTIONS OF LURRICANT:
The presence of lubricating medium between the moving parts greatly
reduces the following:
1. Surface wear and tear and deformation, so that direct contact between
the rubbing surfaces is avoided.
2. Waste of energy in the form of heat, so it acts as a coolant of heat
transfer medium.
3. Expansion of metal by local frictional heat.
4. Unsmooth relative motion.
5. Maintenance and running cost of machine.
6. The power loss in internal combustion (I.C.) engine. In internal
combustion engine, the lubricant acts as a seal between the piston and
cylinder wall. Hence, it prevents the leakage of gases at high pressure.
Applied Chemistry/ Lubricants
Page No. 1
SBMP/ CHEMISTRY DEPT.
TYPES OF LUBRICATION:
Lubrication of machine is unavoidable and plays an important role in the
smooth running of the machine. The lubrication of a machine is done in
various ways depending upon the circumstances under which a machine is
working. There are mainly three types of mechanism by which lubrication
is done to reduce the frictional resistance, wear and damage due to the
surfaces: (i) Fluid film lubrication, (ii) Boundary lubrication, (iii)
Extreme pressure lubrication.
(i) Fluid film lubrication:
1t is done by introducing the liquid lubricants in between the moving or
sliding surfaces. The lubricant film covers or fills the irregularities of the
sliding or moving surfaces and the lubricant forms a thin layer in between
them. This thin layer of lubricant avoids metal to metal contact and reduces
wear and friction. 'The resistance to movement of moving parts is only due
to the internal resistance between the particles of the lubricant moving over
each other.
Thus, in fluid-film lubrication, the lubricant chosen should have the
minimum viscosity under working conditions and at the same time it
should remain in place and separate the surfaces.
This type of lubrication is provided in case of delicate instruments and light
machines like watches, clocks, guns, sewing machines, scientific
instruments etc.
(ii) Boundary lubrication:
This type of lubrication is done when a continuous fluid-film of lubricant
cannot persist and direct metal to metal contact is possible due to certain
reasons. This happens when (i) a shaft starts moving from rest or (ii) the
Applied Chemistry/ Lubricants
Page No. 2
SBMP/ CHEMISTRY DEPT.
speed is very low or (iii) the load is very high or (iv) the viscosity of the oil
is too low. Under such conditions, the space between the moving parts is
lubricated with a thin layer of oil lubricant. The oil is adsorbed (i.e. attached
to surface) by physical or chemical forces or both on the metallic surfaces.
These adsorbed layers cannot get removed easily and thus avoids direct
metal to metal contact. The load is carried by the layers of the adsorbed
lubricant on the metallic surfaces.
The property which is responsible for this kind of adsorption is “oiliness”.
Vegetable and animal oils possess greater oiliness than the mineral oils and
hence these oils possess great property of adsorption. They get either
physically adsorbed to metal surface or react chemically at the metal surfaces
forming a thin film of metal soap, which acts as lubricant. Graphite and
molybdenum disulphide as either alone or as stable suspension in oil are also
used for boundary lubrication under the conditions of very high loads and
temperatures.
(iii) Extreme pressure lubrication:
When the moving surfaces are under very high pressure and there develops
a high temperature, under such conditions, the liquid lubricants fail to stick
and even vapourize. In such cases extreme pressure lubrication is done. To
meet extreme pressure and high temperature conditions, special additives
called "extreme pressure additives" are added to liquid lubricants. These
additives form a more durable film on the metal surface which is capable of
withstanding heavy loads and high temperatures. The additives are organic
compounds having certain active groups or radicals such as chlorine, sulphur
or phosphorus. These compounds react with the metallic surfaces at
prevailing high temperatures to form metallic chlorides, sulphides or
phosphides. These metallic compounds possess high melting points and
Applied Chemistry/ Lubricants
Page No. 3
SBMP/ CHEMISTRY DEPT.
serve as good lubricant under extreme pressure and temperature conditions.
CLASSIFICATION OF LUBRICANTS:
Common lubricants can be classified according to their state into three main
types as given below:
1. Solid lubricants
2. Semi-solid lubricants
3. Liquid lubricants
1.
Solid lubricants: Solid lubricants are used in situations such as:
(a)
(b)
(c)
(d)
Heavy machinery working on a crude job at very high loads and
slow speeds
The film of even lubricating greases cannot be maintained, due to
operating high temperatures.
Where a liquid or semi-solid lubricant film cannot be maintained as
in case of electric motors and generators.
Where parts to be lubricated are not easily accessible.
The examples of solid lubricants are graphite, soap, soap stone, wax, talc,
molybdenum disulphide, chalk, mica etc. The important solid lubricants used
are graphite and soap stone at places where oil film cannot be maintained
due to high temperature. Solid lubricants are used either in the form of dry
powder or suspended in oil, grease or even in water. Soap, soap stones and
waxes are also used in heavy machines. Blocks of such lubricants are fixed
at points near the moving parts when some of it gets powdered and is carried
into the moving surfaces.
Graphite is the most popular among all the solid lubricants. It is quite soft
and does not catch fire. At about 375°C, it gets oxidised in the presence of
air. Therefore it cannot be used above 375°C in the presence of air. In the
absence of air, it can be used upto very high temperatures. Graphite, when
mixed with petroleum jelly to form a graphite grease, serves as a better
lubricant. It becomes stable and can be used at still higher temperatures. This
is used as lubricant for railway track joints, chains, air compressors, open
gears, cast iron bearings, heavy machines such as lathes etc. Solid lubricants
are mostly used for heavy machinery. Recently some stearates and polmitates
of aluminium have also been employed as solid lubricants.
2.
Semi-solid lubricants:
Greases, vaselines, waxes and other compounds of oil and fats are some of
Applied Chemistry/ Lubricants
Page No. 4
SBMP/ CHEMISTRY DEPT.
the semi-solid lubricants. These are called semi-solid, because they are
neither solids nor liquids at ordinary temperature.
Among the semi-solid lubricants, greases are most popular and are used in
the following cases:
(a)
(b)
(c)
(d)
Where the machine parts are subjected to slow speed, heavy load
and sudden jerks.
Where the bearings produce high temperature.
Where the oil gives splashes and spoil the whole machine.
Where the entry of dust or moisture is undesirable. Dust and
moisture spoil the lubricating action.
Greases are the mixtures of petroleum, oils and soaps, which are the sodium
or potassium salts of some higher fatty acids. According to their composition
and methods of preparation, greases may be classified as under:
(a)
(b)
(c)
(d)
Cup greases: These are the emulsions of petroleum oil and water
containing calcium oleate or stearate as stabilizer.
Soda base greases: These are prepared by mixing sodium soaps
with petroleum oil. They are suitable for use near heat and in
different gears.
Lithium soap greases: These are prepared by mixing sodium soaps
with petroleum oils. They are water resisting and suitable for use at
low temperature.
Axle greases: These are prepared by adding lime or any metal
hydroxide and resin to fatty acids. After a thorough mixing, the
whole mixture is allowed to stand when the greases separate out
and set into a stiff mass. They are water resisting and suitable at
higher pressure and low speed.
There are many semi-solid lubricants other than the greases. These are the
mixtures of mineral oils and solids like soap, graphite etc. They are mostly
used in tractor rollers, mil axle boxes, wire ropes, machine bearings etc.
3.
Liquid lubricants
These are mainly lubricating oils. The main function of lubricating oils is to
reduce friction and wear between two sliding or moving metallic surfaces by
maintaining a continuous fluid-film in between them. Besides this, they also
act as (a) cooling medium, (b) sealing agent, and (c) preventer of corrosion.
The liquid lubricants are widely used for the lubrication of delicate and light
Applied Chemistry/ Lubricants
Page No. 5
SBMP/ CHEMISTRY DEPT.
machines which work at high speed, but under low pressure. They are
classified as follows: (a) Mineral oils, (b) Vegetable oils, (c) Animal oils, (d)
Blended oils, (e) Synthetic oils.
a) Mineral oils: These lubricating oils are produced by the fractional
distillation of petroleum at a temperature of about 400°C. The residue
left after distillation of crude petroleum is subjected to further
distillation under certain conditions which separate light oils, heavy
oils and most of the asphalt. The oils are purified so as to remove wax
and other harmful impurities. The wax present in an oil renders the
lubricant useless at low temperatures. It may cause oil to stiffen the
machine parts which will stop the motion of moving parts. Wax and
other unwanted impurities must be removed by a number of processes
such as de-waxing, concentrated sulphuric acid treatment and solvent
treatment etc.
Mineral oils of higher hydrocarbons are quite thick and hence are made
suitable for use by mixing them with thin vegetable oils. Mineral oils
are quite stable, cheap and easily available and hence preferred. The
mineral oils like paraffins, naphthalene are most popularly used.
b) Vegetable oils: These oils are obtained from the vegetable sources.
They were widely used before the discovery of petroleum, but now-adays mineral oils have replaced them. Still they are used in certain
cases. They are added to mineral oils for improving their properties.
Some of the important vegetable oils are: Olive oil, Palm oil, Castor
oil, Hazel Nut oil.
c) Animal oils: These oils are obtained from the animal sources. These
oils resemble vegetable oils. They can be added to mineral oils to
improve their properties. Some of the important animal oils are: Whale
oil, Lard oil (obtained from the kidney, intestines and the fat of pigs),
Tallow oil (prepared from the fat of cattles).
d) Blended oils: When mineral oils are mixed with animal or vegetable
oils to behave as a good lubricant, the mixture is called 'Blended Oil.'
A single oil is rarely a good 1ubricant, but blending oils, a mixture of
suitable oils behaves as a good lubricant. Blending of oils is done to
reduce pour point, improve viscosity, increase oiliness, resist
oxidation, reduce corrosion and to improve colour.
e) Synthetic oils: The synthetic oils are chemically prepared compounds.
Where mineral oil fail to work, synthetic oils are used as lubricants.
They are very effective in severe conditions and are used in jet engines,
rocket motors, submarines etc. These oils are very expensive and
sometimes they are used by mixing them with mineral oils.
Applied Chemistry/ Lubricants
Page No. 6
SBMP/ CHEMISTRY DEPT.
CHARACTERISTICS OF LUBRICANTS:
The characteristic properties must be taken into consideration while selecting a
suitable lubricant for a particular machine. We will study the properties of
lubricants, under two heads:
(a) Physical Tests: (1) Viscosity, (2) Viscosity Index, (3) Oiliness, (4)
Flash point and Fire point, (5) Volatility, (6) Cloud point and Pour
point.
(b) Chemical Tests: (1) Acidity or Neutralisation number, (2)
Emulsification, (3) Saponification value.
(a) Physical Tests:
(1) Viscosity: It is defined as "the force in dynes required to move 1 cm
square of the liquid over another surface with a velocity of 1 cm per
second."
The unit of viscosity is poise. It is an important property of a lubricant
and plays an important role in its selection. It is a measure of internal
resistance of the fluid because of which it can flow slowly or quickly.
Generally, liquids of low viscosity (less viscous liquids) are preferred
for bearings under light load and high speed whereas thick oils having
high viscosity are used for low speed and high pressure bearings. For
sewing machines, guns, watches, clocks, scientific equipment and
fine instruments, liquid lubricants of low viscosity are used. For
heavy machines such as lathes, rail-track-joints, concrete mixtures etc.
thick liquids of high viscosity are used.
(2) Viscosity Index: “The rate of change of viscosity of a liquid (oil) with
temperature is known as viscosity index.”
The viscosity of a liquid varies with the change of temperature. A good
lubricant is that whose viscosity does not change much with temperature.
Due to the motion of machine parts some heat is produced and the
temperature rises. If the viscosity index is very high, then at low
temperatures, the viscosity will increase so much, that the oil will fail to
move into the place and working will stop. On the other hand, at high
temperature, the viscosity will decrease so much that the oil film will fail
to persist and may get squeezed out. A good lubricant should possess
minimum variation in viscosity with temperature i.e. minimum viscosity
index. Therefore, during the selection of a particular lubricant for a
Applied Chemistry/ Lubricants
Page No. 7
SBMP/ CHEMISTRY DEPT.
particular machine, its viscosity and viscosity index should be properly
assessed.
(3) Oiliness: "It is defined as the power of an oil to maintain a continuous
film under pressure while used as a lubricant."
It plays an important role in the selection of lubricant. It is the property of
an oil by virtue of which it sticks on the surface of machine parts working
under high pressure and high temperatures. Lubricants possessing high
oiliness form a continuous oil-film which does not collapse. Liquids
having low viscosity (thin oils) may be having high oiliness than the more
viscous liquids (thick oils). Mineral oils have comparatively low oiliness
than the vegetable oils. The oiliness of the mineral oils can be increased
by the addition of certain fatty acids such as stearic acid or oleic acid etc.
Liquids with the same viscosity may have different oiliness.
A good lubricant should have sufficient oiliness so that it remains in place
and maintains continuous film between the moving or sliding surfaces,
reducing friction and power loss in transmission.
(4) Flash point and Fire point: "Flash point of an oil is the lowest
temperature at which the oil begins to give enough vapours which give
momentary flash of light when a flame is applied to it." The vapours do
not burn continuously, but only for a moment when flame is brought near
it.
"Fire point is the minimum temperature at which the oil gives enough
vapours which catch fire and burn continuously at least for five seconds
when flame is applied to it." Usually the fire points are 5 to 40° C higher
than the flash points.
A lubricant having low flash and fire points is not safe. Because due to
the rubbing of machine parts in contact, some heat is produced even if the
lubricant has been applied in between. As a result, the temperature is
increased. In such cases, a lubricant having low flash and fire points will
catch fire which may cause damage to life and property in a factory.
Therefore, a good lubricant should have high flash and fire points at least
beyond the temperature at which a particular lubricant is to be used.
(5) Volatility: "Volatility of oil is its tendency to vapourise with the increase
of temperature."
If a lubricant is highly volatile, it will vapourise rapidly even at low
temperature. In this case, the consumption of the lubricant is much more
Applied Chemistry/ Lubricants
Page No. 8
SBMP/ CHEMISTRY DEPT.
than the required and hence lubrication process will be costly. Thus a
good lubricant should have low volatility.
(6) Cloud point and Pour point: "Cloud point indicates the temperature at
which the oil becomes cloudy or hazy in appearance, due to separation of
wax."
"Pour point of a liquid is the temperature at which the liquid ceases to
flow on cooling."
The property is important in cold countries because of the fact that the
lubricant used does not become viscous or freezes. A good lubricant
should have low pour point.
Cloud point is of greater importance for fuel oils and pour point for
lubricating oils.
(b) Chemical Tests:
(1) Acidity or Neutralisation number: It is defined as "the number of
milligrams of KOH required to neutralise free acid in one gram of oil."
In order to determine acidity, a known weight of the oil is taken in a
flask, dissolved in 50 % alcohol and titrated against standard solution of
KOH (say N/10 KOH) using phenolphthalein indicator.
The presence of acids in lubricants causes acidity which is harmful to
machine parts because it causes their corrosion. If the acidity (more than
0.1) increases, then the lubricant suffers oxidation during its action. A
good lubricant is that which does not contain free acids. Properly refined
lubricants are mostly free from acids and hence can be used. The acid
value of a good lubricating oil should be less than 0.1.
(2) Emulsification: This is an important property which should be tested
while selecting a good lubricant. Certain oils have the tendency to mix
with water to form an intimate and stable mixture called 'emulsion' and
the process is known as 'emulsification'.
The emulsion has the property of absorbing dust particles and the other
foreign matter present in the surroundings. The solid particles present in
the emulsion cause abrasion of the metals in contact and hence the
lubricating action of the oil is spoiled. A good lubricant is that which
does not form any emulsion and if it is formed, it should not remain for
long time and should break quickly. This property of an oil to separate
Applied Chemistry/ Lubricants
Page No. 9
SBMP/ CHEMISTRY DEPT.
itself, as soon as emulsion is formed, is known as 'demulsification.' The
lubricants should be used in the refined form because in that case, the
chances of emulsion formation would be minimum.
(3) Saponification value: It is defined as "the number of milligrams of KOH
required to saponify (turn into soap) 1 gm of the oil."
The saponification value of vegetable oils is higher as compared to that
of mineral oils. With the help of saponification value, we can know
whether the oil is vegetable, animal or mineral. The oil reacts with KOH
thereby forming glycerol and soap, e.g.
A good lubricant should have moderate saponification value.
SELECTION OF LUBRICANT:
1. The selection of the lubricant for a certain type of machine requires the study
of the conditions under which the lubricant is used such as "speed of moving
parts, intensity of pressure and heat produced." No single lubricant comes to
the standard and in many cases a mixture of lubricants have to be used.
2. The lubricant selected should neither be very thin nor very thick.
3. It should form the continuous layer in the moving parts of the machine under
pressure.
4. It should not get stuck to moving parts and thus prevent the movement of the
various parts.
Thus the selection of a lubricant presents difficulties and after a long
experimentation a particular lubricant can be selected for a specific purpose. The
lubricants used for various types of machinery are given in Table below:
Applied Chemistry/ Lubricants
Page No. 10
SBMP/ CHEMISTRY DEPT.
Types of mechanism and lubricants used
Sr.
Type of Job
No.
1. Delicate
instruments (like
watches, clocks,
sewing machines,
scientific
equipments)
2. Machinery in
which extreme
pressure and low
speeds are
employed (such as
in tractor rollers,
lathes, railway
track joints,
concrete mixtures
etc.)
3. Machinery in which
high pressures and
low speeds are
employed, (such as
rail axle boxes,
wire ropes etc.)
4. Gears
5.
Cutting tools used
in cutting, turning
and grinding of
metals.
Applied Chemistry/ Lubricants
Nature of Job and
properties of Lubricant
These instruments are not
exposed to high
temperatures, heavy loads
or water.
Lubricant selected
Thin vegetable and
animal oils like palm
oil, hazel nut oil etc.
Grease or thick oil film
cannot be maintained.
Solid lubricants like
graphite soap-stone,
mica, molybdenum
disulphide are most
commonly used.
Thin oils cannot be used
for these applications
because they may be
squeezed out due to high
pressure.
Greases or thick oils
or thick blended oils
are employed.
Subjected
to
extreme
pressures. Hence lubricant
should possess: (i) good
oiliness (ii) High oxidation
stability (iii) High load
bearing capacity.
Due to high friction
between tool and metal
work piece results in
liberation of large amount
of heat. Lubricants or
cutting fluids should (i) cool
the tool (ii) cool the metal
work piece (iii) reduce
power consumption (iv)
improve surface finish.
Thick mineral oils
containing extreme
pressure additives
(like metallic soaps)
are used.
(i) Mineral oil of
low viscosity
containing
additives like
fatty oils are
used for heavy
cutting tools.
(ii) Oil-emulsions
are used for
light cutting
tools.
Page No. 11
SBMP/ CHEMISTRY DEPT.
6.
7.
8.
Internal combustion Lubricant in an internal
(I.C.) engine
combustion engine is
exposed to high
temperatures. So high
viscosity index, thermal
stability of lubricant are
required.
Steam engine
Oil is injected drop wise
cylinders
into the steam line. The oil
is atomised by steam and it
is spread on the surfaces of
cylinder walls, piston valve
etc. So oil should possess:
(i) metal wetting quality
(ii) high viscosity
(iii) emulsification with
water.
Steam turbines
Lubricant is exposed to
high temperature and
oxidising conditions.
Moreover lubricant comes
in contact with water due to
leakage, so it should
possess good
demulsification property.
Applied Chemistry/ Lubricants
Mineral oils
containing additives
are used.
High viscosity
mineral oils mixed
with additives like
animal or vegetable
oils are used.
Blended oils
containing additives
which impart
oxidation stability,
corrosion resistance
and demulsification
property.
Page No. 12
SBMP/ CHEMISTRY DEPT.
Chapter 7: Non-Metallic Engineering Materials
Plastics
1) Define Plastics
 Plastics are synthetic, organic materials of high molecular weight which can be molded into any
desired shape by the application of heat, pressure and in pressure of catalyst.
2) Define Polymerization
 The process in which a large number of small molecules (monomers) link together to form a
large molecule (polymer) under specific condition of temperature pressure and in pressure of
catalyst is known as polymerization.
Types of Polymerization: A. Addition polymerization
B. Condensation polymerization
3) Explain Addition polymerization with an example.
 Addition polymerization is a process in which the monomers undergo repeated addition to form
long chain polymers without elimination of simple molecules like H2O and HCl
E.g. Polymerization of ethylene to form polythene
In formation of polythene the monomers is ethylene or ethane i.e. H2C = CH2
In this process the double bond between carbon atoms break forming unstable ethylene
molecules.
𝐻𝑒𝑎𝑡, 𝐿𝑖𝑔ℎ𝑡, 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑟 𝐶𝑎𝑡𝑎𝑙𝑦𝑠𝑡
𝑛[𝐶𝐻2 = 𝐶𝐻2 ] →
Ethylene Molecule
𝑛[𝐶𝐻2 − 𝐶𝐻2 ]
Unstable Ethylene Molecule
These unstable ethylene molecules combine in large numbers to form polythene.
𝑛[𝐶𝐻2 − 𝐶𝐻2 ] + 𝑛[𝐶𝐻2 − 𝐶𝐻2 ] →
𝑛[𝐶𝐻2 − 𝐶𝐻2 − 𝐶𝐻2 − 𝐶𝐻2 ]
4) Explain Condensation polymerization with an example.
 Condensation polymerization is a process in which different types of monomers are linked
together by condensation to form a large polymer with elimination of small molecules like H2O
& HCl.
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 1
SBMP/ CHEMISTRY DEPT.
Example: Formation of Bakelite
It is prepared by condensing phenol and formaldehyde in presence of acidic or alkaline medium.
5) Types of Plastic.
 There are two types of plastici.
Thermosoftening Plastic or thermoplastic
ii.
Thermosetting Plastic
6) Distinguish between Thermosoftening Plastic and thermosetting Plastic.
Thermosoftening Plastic
Thermosetting Plastic
They are formed by addition polymerization
They are formed by condensation
polymerization
These plastics once hardened cannot be
softened again
They have a cross linked structure
They are insoluble in organic solvents
They are strong, hard, and more brittle
It can be re-moulded and reused
They soften on heating and harden on cooling
They have a linear structure
They are soluble in organic solvents
They are soft, weak and less brittle
It can be re-moulded and reused
7) Explain compounding of plastics.
 Compounding of plastic is a process in which some substances are added to plastic to improve
the property, quality of plastics.
Substances added arei) Resins: They are organic polymers which act as building material.
ii) Fillers: They are added to increase the hardness, tensile strength, heat resistance and to
decrease the cost. E.g. Asbestos, quartz, mica, sawdust.
iii) Plasticizers: These are added to increase plasticity of plastic E.g. Camphor, Triphenyl
phosphates.
iv) Accelerators or Catalyst: These increase the speed of polymerization reaction. E.g. H2O2, Pb,
Ag, etc.
v) Pigments: These impart desired color to plastic. E.g. organic dyes.
8) PVC is soft whereas Bakelite is hard. Give reason.
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 2
SBMP/ CHEMISTRY DEPT.
 PVC is thermoplastic and the intermolecular bonds in thermoplastic are week and they have
linear structure. Whereas the intermolecular bonds in thermosetting plastics are strong and
they have cross linked structure. Thus PVC is soft whereas Bakelite is hard.
9) State the properties and applications of plastics?
 Properties and their related applications are:
i) Low specific gravity and high tensile strength.
Use: In aircrafts and automobile industries.
ii) Bad conductor of heat and electricity.
Use: For making handles of pressure cooker, iron, TV knobs.
iii) Chemical and corrosion resistance.
Use: In chemical industries, in making pipes, tubes, tanks, etc.
iv) Abrasion Resistance
Use: For making machinery parts such as gears.
v) Optical clarity and good strength.
Use: To make wind screens for automobile and aircrafts.
vi) Hard and shock absorbing capacity.
Use: In machinery to reduce noise and vibration
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 3
SBMP/ CHEMISTRY DEPT.
RUBBER
10) Define Rubber.
 Rubber is an organic polymer of isoprene which can undergo large elongation at relatively low
stress.
11) Which organic compound is present in rubber?
 Isoprene is present in rubber.
12) Explain the process how rubber is obtained from latex?
 Latex is obtained from the bank of a rubber tree. Latex consists of 30% - 40% rubber.
Process of obtaining rubber:
Latex is first diluted with water and filtered to remove dirt and impurities.
To filtrate 5% acetic acid is added as coagulant.
Thus rubber is coagulated (i.e. settled at the bottom) washed, dried and further processed.
13) Give the drawbacks of natural rubber. OR Why is it necessary to vulcanize natural rubber?
 Drawbacks of natural rubber are:
i) It undergoes permanent deformation on stretching.
ii) It undergoes oxidation in air.
iii) Its tensile strength is low.
iv) It absorbs large quantity of water.
v) It becomes soft and sticky in summer and hard in winter.
vi) It reacts with solvents.
14) Describe the process of vulcanization of rubber.
 Vulcanization is the process of heating raw rubber with sulphur to high temperature to increase
the stiffness of rubber.
During Vulcanization, Sulphur gets added to the isoprene molecules in rubber forming cross
linked structure
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 4
SBMP/ CHEMISTRY DEPT.
The ebonite obtained is stiff, tough & abrasion resistant and has good electrical insulating
property.
15) What is synthetic rubber? State its example.
 Synthetic Rubber: Any vulcanizable artificially prepared rubber like product having the property
of elasticity is called synthetic rubber.
E.g. Buna-S, Buna-N, Butyl rubber, neoprene.
16) Distinguish between Natural Rubber and Synthetic Rubber.
Natural Rubber
Synthetic Rubber
It is naturally occurring polymer
It absorbs water
It becomes soft in summer and hard in winter
It is made by artificial rubber like product
It is water resistant
It neither becomes soft in summers nor hard in
winters.
It does not oxidize in air
It does not undergo permanent deformation on
stretching
Its tack property is low
Its tensile strength is high
It oxidizes in air
It undergoes permanent deformation on
stretching
Its tack property is high
Its tensile strength is low
17) Write the important properties of rubber and its related applications.
 Properties of rubber are:
i) Elasticity: It is a property due to which a material undergoes deformation under stress and
regains its original shape on removal of stress
Use: For making rubber bands, tubes for bicycles, automobiles, aircrafts etc.
ii) Tack: It is the property if rubber by which two or more surfaces stick to each other.
Use: For making tyres.
iii) Rebound: Ability to absorb energy and return without permanent deformation of synthetic
rubber is called rebound.
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 5
SBMP/ CHEMISTRY DEPT.
THERMAL INSULATORS
INTRODUCTION:
“The materials which are used to prevent the flow of heat are known as thermal
insulators.”
The use of thermal insulators is very important in various industrial and
engineering operations where the flow of heat is to be prevented. For example,
in cold storage refrigerators, boilers, ovens, stem carrying pipes, brine pipe
lines etc. all needed thermal insulators.
The good thermal insulators have extremely low thermal
conductivity. The most commonly used thermal insulators are glass, wool,
thermocole, asbestos and cork.
FACTORS AFFECTING THE THERMAL CONDUCTIVITY OF
INSULATORS:
1. Moisture: The thermal conductivity of the material is increased by
the presence of moisture in the pores, because of the fact that air in the
pores is replaced by highly conducting water vapours. Hence the
surface of the thermal insulator should be water-proof. Moreover
the pores on the surface should be as close as possible, so that
moisture cannot enter them. The insulating material should not react
with water.
2. Pores: Common insulating materials are generally the mixture of
fibrous or cellular granular materials. The entrapped air or gases in
pores have low thermal conductivity and so may act as thermal
insulators by preventing the flow of heat to a great extent; but
the transfer of heat by convection increases as the pore volume
increases. Because in large enclosed space greater convection
currents are formed. Consequently, the thermal conductivity
of a material can be decreased and hence, the insulating power can
be increased by modifying the pore structure of the material to be
used as thermal insulator. Therefore a large number of fine pores are
preferred than the few large ones.
CHARACTERISTICS OF GOOD INSULATING MATERIALS
A good insulator has the following important characteristics:
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 6
SBMP/ CHEMISTRY DEPT.
1.
2.
3.
4.
5.
6.
It should be cheap.
It should be fire-proof.
It should possess extremely low thermal conductivity.
Its density should be low.
It should be water-proof and hence resist absorption of moisture.
It should be chemically inert to water surrounding atmosphere and
high temperature.
7. It should be odourless during the use.
8. It should be capable of bearing the load applied on it during working.
9. It should be physically and mechanically stable at the working
temperatures.
10. It should withstand the effects of shock and vibrations.
CLASSIFICATION OF THERMAL INSULATORS:
Thermal insulators are of two types:
1.
2.
Organic thermal insulators: These are suitable for low
temperature work, upto 150°C. These are naturally occurring
materials such as wool, cotton, silk, paper, charcoal, powder saw
dust, coke powder, rubber etc. which generally have low density and
possess very large number of small air pockets.
Inorganic thermal insulators: These are suitable for temperatures
higher than 150°C. These includes asbestos paper, asbestos fibre
(felted), glass fibre, glass wool, mineral slag fibres, calcium silicate,
porous silica, refractory insulating bricks etc.
The most commonly used thermal insulators are: (1) Glass wool and (2)
Thermocole.
GLASS WOOL:
Glass-wool is a fibrous wool like material which is made up of
intermingled fine filaments of glass, like ordinary wool.
Preparation: Glass filaments are obtained by forcing molten mass of
alkali free glass through sieve holes having the average diameter of
0.0005 cm continuously. The filaments of glass so obtained are thrown
over a rapidly revolving drum to get the material in wool -like form.
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 7
SBMP/ CHEMISTRY DEPT.
Properties:
1.
2.
3.
4.
5.
6.
7.
Its density is low.
Its thermal conductivity is low. (about 0.034 kcal/m2/°C/hr).
Its electrical conductivity is also low.
It is fire-proof and non-combustible.
Its average diameter of fibre is 0.0005 cm.
It is resistant to the chemicals and does not ab sorb moisture.
Its tensile strength is about eight times more than steel.
Uses:
1. It is widely used as thermal insulating material in domestic and
industrial appliances such as motors, ovens, refrigerators, walls
and roofs of houses, because it is soft, heat-proof, fire-proof,
flexible and even insect-proof.
2. Being resistant to chemicals, glass-wool is used as a filtering
material for corrosive liquids like acids and acidic solutions in
industry.
3. It is also used in air-filters as dust filtering material.
4. It is used for sound and electrical insulation.
5. It is used in manufacturing fibre glass by reinforcing with plastic
resins.
THERMOCOLE:
“Thermocole is a foamed plastic obtained by blowing air through molten
polysterene or polyurethanes.” It is spongy, porous (having 3 to 6 million
fine air cells or pores per litre) foam like in structure. Because of the
large number of air cells, it possesses an outstanding insulatin g
property.
Properties:
1.
2.
3.
4.
5.
6.
7.
8.
Its density is low (22 kg/m3).
It is spongy, porous and has foam-like structure.
It is quite strong, though extremely light.
It is quite shock-proof.
It is chemically inert and resists ageing.
Its thermal conductivity is low (0.27 kcal/m2/°C/hr).
Its electrical conductivity is also low.
It can be used upto 55°C.
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 8
SBMP/ CHEMISTRY DEPT.
Uses:
1. Being light and shock-proof, thermocole is used as an ideal
packing material for delicate electrical and electronic
equipments.
2. Due to outstanding thermal insulating properties, it is mainly
used as heat insulator in refrigeration and air conditioning.
3. It is used for decorative purposes.
4. It is used for decorative purposes.
5. It is used for protecting screens in radars.
ASBESTOS:
It is a suitable insulator for heat insulation of boiler and for full head lining
a board ship. Asbestos sheets are use d for roof-covering. Asbestos
sheets are durable, fire -resistant, weather- r e s i s t a n t a n d l i g h t i n
weight. They do not require paintings. Their cost of maintenance
is negligible. Asbestos is also used as damp -proofing for walls and floor
in the form of asbestos felt. It is also a good sound insulator. It is used
as a filler for natural and synthetic insulating resins.
CORK:
It is the name given to light bark of an oak tree. The bark is cleaned,
ground, sized and backed into moulds. During backed, its natural resin
comes out and acts as a binding material. It is then converted into thin
sheets by pressing. These sheets are light, porous and resists water and
acts as an insulating material against heat and electricity.
Uses:
1.
2.
3.
4.
5.
Cork is used as a lining material for cold storages,
refrigerators, bottle stoppers and packing gaskets.
It is used in floats of fishing nets.
Floor-tiles, walls and ceilings are made sound -proof with cork
board.
In shoe industry cork sheet is used as a cold filler and
cushioning.
In water-proof coatings, linoleums etc.
In making base for telephones, bulletin-boards and sporting equipment
grips etc.
Applied Chemistry/ Non-Metallic Engineering Materials
Page No. 9
MCQ Question BANK All Chapters
Ch.
1
1
1
1
1
Q.
No.
Question
1 “In an atom, electrons occupy available orbitals in the increasing order
of energy” ---- is the statement for
“In an atom, when degenerate orbitals are available, the electrons first
2 fill all the orbitals with parallel spin before paring in any one orbital” :
is the statement for
“It is impossible to know the exact position and velocity of the electron
3
simultaneously” : is the statement for
4 “No two electrons in the same atom can have identical set of four
quantum numbers”: is the statement for
5 An element has 18 electrons and 20 neutrons. What is its Mass
number?
Answer
Aufbau’s Principle
Hund’s Rule
Heisenberg’s
Principle
Pauli’s Exclusion
Principle
38
1
6 Atomic mass of an element is equal to the sum of
Mass of protons &
neutrons
1
7 Atomic number is equal to
Number of protons
1
8 Chlorine's (Cl) relative atomic mass is 35.5. this half number is due to
isotopes
1
9 Electron is a fundamental particle which carries
No mass and
negative charge
1
10 Elements with 1-3 valence electrons are called
metals
1
11 Elements with 4-7 valence electrons are referred to as
non-metals
1
12 If number of protons of an element changes
it will become
another element
1
13 Neutron is a fundamental particle which carries
No charge and
mass of 1 unit
1
14 Neutrons were discovered by
Chadwick
1
15 Noble gases are
mono atomic
1
16 Number of electrons in phosphorus (P) is 15. Valence electrons shall
be
1
17 Proton is a fundamental particle which carries
1
18 The Basicity of Acetic Acid CH3COOH is
1
19 The isotope atoms differ in
atomic weight
1
20 The number of electrons gained/ lost/ shared by an atom in a chemical
bond is known as
valency
1
21 What does nucleus of atom contain?
protons and
neutrons
1
22 Who proposed first atomic theory?
John Dalton
2
23 _______ acts as anode in dry cell.
Zn
2
24 _____________________ are strong electrolytes.
CuSO4, NaCl, KCl
2
25 _____________________ are weak electrolytes.
CH3COOH,
NH4OH
Applied Chemistry MCQ
5
1 unit mass and
positive charge
1
Page No. 1
2
26 ______________________ are non-polar solvents.
Benzene, Acetone,
Ether
2
27 ______________________ is a polar solvent.
Water
2
28 An atom or a group of atoms with charge is called as ____________
Ion
2
29 Anions are formed by
gain of electrons
2
30 Battery is a type of _________ cell.
Electrochemical
2
31 Cations are formed by
loss of electrons
2
32 Degree of dissociation is ____________ temperature.
2
33 Degree of dissociation is _______________ concentration.
2
34 Degree of ionisation is _______________ concentration.
2
35 Degree of ionisation is _______________ temperature.
directly
proportional to
inversely
proportional to
inversely
proportional to
directly
proportional to
2
36 Dry cell is an example of __________cell.
2
2
2
2
37 Electrochemical cell is a device which is used to get __________
energy.
38 Electrolyte used in electro-chemical reaction should be an ionic
compound in
39 Electrolyte used in electro-chemical reaction should be an ionic
compound in
40 Electrolyte used in electro-chemical reaction should be an ionic
compound in
Primary
Electrical
solution state
fused state
molten state
splitting of an ionic
compound into ions
degree of
dissociation
2
41 Electrolytic dissociation is
2
42 Fractions of molecules undergoing dissociation is
2
43 Fractions of molecules undergoing dissociation is
degree of ionisation
2
44 Fractions of molecules undergoing ionisation is
degree of ionisation
2
45 Ionic compounds undergo ionisation only in
Liquid state
2
46 Ionisation is
splitting of an ionic
compound into ions
2
47 Ionisation is a ________________ process.
reversible
2
48 Only _______________ compounds undergo ionisation.
Electrovalent
compound
2
49 Shape of electrodes should be
any shape
2
The charge in a solution is neutral because
50
2
2
2
51 The charge on an ion is equal to its
52 The process in which one metal is coated on the other metal with the
help of electric current is known as
53 The total charge in a solution is
Applied Chemistry MCQ
total positive
charge on cations =
total negative
charge on anions
valency
Electroplating
neutral
Page No. 2
Why do ionic substances conduct electricity in solution or molten state
but not in solid state?
2
54
when in solution or
molten state, ions
are free to move
but not in solid
state
fusion ,
compression,
electrodeposition
3
55 ________________ are methods of preparing alloys.
3
56 ________________ is a method of refining metals.
Electrorefining
3
57 Ability of the metal to resist penetration is
hardness
3
58 Ability of the metal to resist wear or abrasion is
hardness
3
59 Alloys containing Fe are called
Ferrous alloys
3
60 Alloys containing Hg are called
Amalgam
3
61 Alloys containing mercury and a metal are called
Amalgam
3
62 Aluminium amalgam is
Al and Hg
3
63 An alloy is a ______________ mixture of two or more metals.
homogeneous
3
64 An alloy is a mixture of
metal and a nonmetal
3
65 An alloy must have at least one
metal
3
66 Arsenic and Antimony are examples of
Metalloids
3
67 Babbit metal is an alloy of
Sn, Sb, Cu
3
68 Brass is an alloy of
Cu and Zn
3
69 Bronze is an alloy of
Cu and Sn
3
70 Bronze is an alloy of
Cu and Sn
3
71 Calcination and Roasting are processes carried out in:
3
72 Calcination is
Reverberatory
Furnace
process of heating
the ore strongly in
the absence of air
3
73 Calcination is carried out for
oxide ores
3
74 Calcination is carried out in a
reverbaratory
furnace
3
75 Calcination is the process of heating the ore strongly in
absence of oxygen
3
76 Chemical methods of concentration are
3
77 Composition of brass is
3
78 Composition of brass is
calcination and
roasting
30% of Zn and
70% of Cu
70% of Cu and
30% of Zn
3
79 Copper is added to gold to
improve hardness
3
80 Copper is added to silver to
improve hardness
Applied Chemistry MCQ
Page No. 3
3
81 Distillation is a method of
refining of metals
3
82 Ductility is the property by virtue of which the metal can be
drawn into wires
3
83 Ductility is the property of a metal where the metal is
drawn into thin
wires
3
84 Duralumin contains
Al, Cu, Mg, Mn
3
85 Duralumin mainly contains
Al
3
86 During calcination and roasting, the ore is chemically converted into
oxides
3
87 During the froth flotation process, the sulphide ore is mixed with
oil and water
3
Electromagnetic separation is used for
88
separating
magnetic impurities
from non-magnetic
ores
3
89 Elements which behave like metals and non-metals are
metalloids
3
90 Example of metalloid is
arsenic
3
91 Example of metalloid is
Antimony
3
92 Example of non-metals is
Helium
3
93 Froth Flotation is a method of concentration for
Sulphide Ores
3
94 Froth flotation is a process used for concentration of
sulphide ores
3
95 Giving shapes by pouring molten metal into a mould is
casting
3
96 Gun metal contains
Cu, Sn and Zn
3
97 In soldering, the alloy used is
non-ferrous with
melting point
below 400 °C
3
98 In the process of froth flotation the sulphide particles are
wetted by oil
3
99 In the process of froth flotation, the gangue
sinks to the bottom
3
100 In the process of froth flotation, the sulphide particles
forms the top layer
3
101 Liquation is a method of
refining of metals
3
102 Magnalium mainly contains
Al
3
103 Magnalium mainly contains
Al and Cu
3
104 Malleability is a property of metal where the metal is
beaten into sheets
3
105 Malleability is the property by virtue of which the metal can be
beaten into sheets
which behave like
metals and nonmetals
a process of
extraction of metals
3
106 Metalloids are elements
3
107 Metallurgy is
3
108 Metallurgy is extracting metals from
ores
3
109 Metals which are often used to make coins are
bronze
Applied Chemistry MCQ
Page No. 4
3
110 Metals which can be casted should
expand slightly on
cooling
3
111 Mineral from which metals can be extracted economically are
Ore
3
112 Minerals are
naturally occurring
metal compounds
3
113 Monel metal is an alloy of
Cu, Ni, Fe, Mn
3
114 Most of the alloys are
solid
3
115 Naturally occurring metallic compounds are
minerals
3
116 Ni and Cr are added to stainless steel to make it
corrosion resistance
3
117 Non-sulphide ores are concentrated by
Froth Floatation
3
118 One of the physical methods of concentration of ores is
gravity separation
3
119 One of the physical methods of concentration of ores is
froth flotation
3
120 One of the physical methods of concentration of ores is
magnetic
separation
3
121 Opposite of toughness is
brittleness
3
Ores are
122
mineral from which
metals can be
extracted
economically
magnetic
separation
3
123 Physical method of concentration of tinstone ore is
3
124 Poling is a method of
refining of metals
3
125 Principle of gravity separation is
difference in the
density of ore and
gangue particle
3
126 Process of removal of gangue from the ores is
concentration
3
127 Property of the metal by which it can be drawn into wires is
ductility
3
128 Purification of metal is known as
refining
3
129 Roasting is carried out for
sulphide ores
3
130 Roasting is carried out in
presence of air
3
131 Roasting is carried out in
presence of oxygen
3
132 Roasting is carried out in a
3
133 Separating magnetic impurities from non-magnetic ores is done by
reverberatory
furnace
magnetic
separation
3
134 Slag is a chemical compound formed by combination of
flux and gangue
3
135 Small amount of impurities in copper
decreases its
conductivity
3
136 Sodium amalgam is
Na and Hg
3
137 Sulphide ores are concentrated by
Froth Flotation
Applied Chemistry MCQ
Page No. 5
welding, soldering
& brazing
weight which its
wire can support
resistance to
abrasion
3
138 Techniques of joining pieces of metals are
3
139 Tenacity of the metal is measured by
3
140 Tensile strength of the metal is measured by
3
141 The addition of carbon to iron increases its
tensile strength
3
142 The hardest metal known is
tungsten
3
143 The main element in babbit metal is
Sn
3
144 The melting point of an alloy is ____________ than its constituent
elements.
145 The metallurgical process in which a metal is obtained in a fused state
is called
146 The process in which the metal pieces are given shapes by compressive
forces at high temperature is
147 The process in which the metal pieces are given shapes by forcing
through a die orifices is
148 The process of concentration of non-sulphide ores is
3
149 The process of concentration of oxide ores is
3
3
3
3
3
lower
smelting
forging
extruding
gravity separation
gravity separation
The process of froth flotation is based on the principle of
preferential
wettability of
sulphide ores by oil
and gangue by
water
150
3
151
The process of joining two pieces of metals by introducing a molten
non-ferrous alloy with melting point below 400°C is
soldering
3
152
The process of joining two pieces of metals by introducing a molten
non-ferrous alloy with melting point above 400°C is
brazing
3
153 The process of joining two pieces of metals by means of heat is
weldability
3
154 The process suitable for the concentration of sulphide ores is
froth flotation
3
155 The property by virtue of which the metal can be hammered into
shapes is
156 The property of metal by virtue of which it can be given shape by
applying pressure at high temperature is
157 The property of metal by virtue of which its weight carrying capacity is
measured is
158 The property of metal by virtue of which its weight supporting capacity
is measured is
159 The property of metal by virtue of which the metal resists repeated
shocks or vibrations is
160 The softest metal known is
3
161 Toughness is the property by virtue of which the metal
resists repeated
shocks and
vibrations
3
162 Unwanted impurities associated with the ores are called as
gangue
3
163 When aluminium and carbon fail as reducing agents in metallurgy then
the process used is
electrolytic
reduction
3
3
3
3
3
Applied Chemistry MCQ
malleability
forging
tensile strength
tenacity
toughness
potassium
Page No. 6
aluminothermic
reduction
3
164 When Aluminium is used as a reducing agent, the process of reduction
is called
165 When alumium is used as a reducing agent in metallurgy then the
process is called
166 When carbon is used as a reducing agent in metallurgy then the process
is called
167 When carbon is used as a reducing agent, the process of reduction is
called
168 When preparing the alloy by fusion method, heavy metals
3
169 Which one of the following is the softest?
sodium
3
170 Zinc amalgam is
Zn and Hg
4
171 Caustic embrittlement is due to dissolved
Na salts
4
172 Caustic embrittlement is due to dissolved
Na2CO3
4
173 Chloride content of water is estimated by titrating water against
AgNO3
4
174 Cooking food using hard water
4
175 Cooking food using hard water
4
176 Formation of sludge in the boiler
4
177 Hardness causing salts in water
4
178 Hardness of water is because it has
good solubility
4
179 Hardness of water is due to
Ca+2
4
180 Hardness of water is due to
salts of Ca and Mg
4
181 Hardness of water is due to
CaCl2
4
182 Hardness of water is due to
Ca(HCO3)2
4
183 Hardness of water to be used in boilers should be
0-10 ppm
4
184 If hard water is used in dyeing industry then
impure shades of
dyes are produced
4
185 If hard water is used in dyeing industry then
impure shades of
dyes are produced
4
186 If hard water is used in paper industry, paper becomes
yellow
4
187 If hard water is used in paper industry, paper becomes
rough
4
188 If hard water is used in sugar industry, sugar becomes
deliquescent
4
189 If hard water is used in sugar industry, sugar crystals become
small
4
190 If pH of a solution is 1 then Hydrogen ion concentration will be
10-1
4
191 If pH of a solution is 1 then Hydrogen ion concentration will be
10-1
3
3
3
3
Applied Chemistry MCQ
alumino thermic
smelting
smelting
are added at the end
increases the
consumption of
fuel
decreases the life of
utensils
chokes the
pipelines
increase the boiling
point
Page No. 7
4
192 If pH of a solution is 1 then Hydroxyl ion concentration will be
10-13
4
193 If pH of a solution is 1 then Hydroxyl ion concentration will be
10-13
4
194 If pH of a solution is 10 then Hydrogen ion concentration will be
10-10
4
195 If pH of a solution is 10 then Hydrogen ion concentration will be
10-10
4
196 If pH of a solution is 10 then Hydroxyl ion concentration will be
10-4
4
197 If pH of a solution is 11 then Hydrogen ion concentration will be
10-11
4
198 If pH of a solution is 11 then Hydrogen ion concentration will be
10-11
4
199 If pH of a solution is 11 then Hydroxyl ion concentration will be
10-3
4
200 If pH of a solution is 12 then Hydrogen ion concentration will be
10-12
4
201 If pH of a solution is 12 then Hydrogen ion concentration will be
10-12
4
202 If pH of a solution is 12 then Hydroxyl ion concentration will be
10-2
4
203 If pH of a solution is 13 then Hydrogen ion concentration will be
10-13
4
204 If pH of a solution is 13 then Hydrogen ion concentration will be
10-13
4
205 If pH of a solution is 13 then Hydroxyl ion concentration will be
10-1
4
206 If pH of a solution is 14 then Hydrogen ion concentration will be
10-14
4
207 If pH of a solution is 14 then Hydrogen ion concentration will be
10-14
4
208 If pH of a solution is 14 then Hydroxyl ion concentration will be
10-0
4
209 If pH of a solution is 14; nature of this solution is
extremely basic
4
210 If pH of a solution is 2 then Hydrogen ion concentration will be
10-2
4
211 If pH of a solution is 2 then Hydrogen ion concentration will be
10-2
4
212 If pH of a solution is 2 then Hydroxyl ion concentration will be
10-12
4
213 If pH of a solution is 2 then Hydroxyl ion concentration will be
10-12
4
214 If pH of a solution is 3 then Hydrogen ion concentration will be
10-3
4
215 If pH of a solution is 3 then Hydrogen ion concentration will be
10-3
4
216 If pH of a solution is 3 then Hydroxyl ion concentration will be
10-11
4
217 If pH of a solution is 3 then Hydroxyl ion concentration will be
10-11
4
218 If pH of a solution is 4 then Hydrogen ion concentration will be
10-4
4
219 If pH of a solution is 4 then Hydrogen ion concentration will be
10-4
4
220 If pH of a solution is 4 then Hydroxyl ion concentration will be
10-10
4
221 If pH of a solution is 4 then Hydroxyl ion concentration will be
10-10
4
222 If pH of a solution is 5 then Hydrogen ion concentration will be
10-5
4
223 If pH of a solution is 5 then Hydrogen ion concentration will be
10-5
Applied Chemistry MCQ
Page No. 8
4
224 If pH of a solution is 5 then Hydroxyl ion concentration will be
10-9
4
225 If pH of a solution is 6 then Hydrogen ion concentration will be
10-6
4
226 If pH of a solution is 6 then Hydrogen ion concentration will be
10-6
4
227 If pH of a solution is 6 then Hydroxyl ion concentration will be
10-8
4
228 If pH of a solution is 7 then Hydrogen ion concentration will be
10-7
4
229 If pH of a solution is 7 then Hydrogen ion concentration will be
10-7
4
230 If pH of a solution is 7 then Hydroxyl ion concentration will be
10-7
4
231 If pH of a solution is 8 then Hydrogen ion concentration will be
10-8
4
232 If pH of a solution is 8 then Hydroxyl ion concentration will be
10-6
4
233 If pH of a solution is 9 then Hydrogen ion concentration will be
10-9
4
234 If pH of a solution is 9 then Hydrogen ion concentration will be
10-9
4
235 If pH of a solution is 9 then Hydrogen ion concentration will be
10-9
4
236 If pH of a solution is 9 then Hydrogen ion concentration will be
10-9
4
237 If pH of a solution is 9 then Hydroxyl ion concentration will be
10-5
4
238 If pH of a solution is zero; nature of this solution is
extremely acidic
4
239 If water used in paper industry contains iron salts then paper
develops brown
spots
4
240 If water used in paper industry contains manganese salts then paper
becomes yellowish
4
241 Permanent hardness is caused by
sulphates and
chlorides of Ca
4
242 Permanent hardness is caused by
sulphates and
chlorides of Mg
4
243 pH of a solution whose H+ ion concentration is 10-1 is
1
4
244 pH of a solution whose H+ ion concentration is 10-2 is
2
4
245 pH of distilled water is
7
4
246 Quantities of salts which cause hardness are converted into
CaCO3 equivalent
4
247 Temporary hardness is caused by
bicarbonates of Ca
and Mg
4
248 The compound which causes permanent hardness in water is
CaSO4
4
249 Total hardness of water is estimated by titrating water against
4
250 Units of hardness of water are
4
251 Washing clothes using hard water and soap increases
5
252 "Alclad" sheets are
EDTA, Soap
Solution
ppm, mg/litre,
degree Clarke,
degree French
consumption of
soap
Al sheets cladded
with Duralumin
Applied Chemistry MCQ
Page No. 9
5
253 _____ & ________ metals could provide cathodic protection to Fe.
Al & Zn
5
254 ______ is the process of coating of tin over Fe or steel.
Tinning
5
255 _______ coating is non toxic in nature.
Sn
5
256 _________ is inert to oxidation.
Pt
5
257 _________ is the process of coating Fe or steel with a zinc coating.
Galvanizing
5
258
5
259 ____________ are added to paints to adjust their consistency.
Thinners
5
260 ____________ is a transparent coating.
Thinners
5
261 _____________ is a dispersion of resin in oil or spirit.
Varnish
5
______________ sheets cannot be used to make utensils for storing food
Galvanised
262 stuffs.
5
263 A colloidal dispersion of resins in methylated spirit is known as
__________ is used for producing a coating of low melting metal such
as Zn, Sn, Pb, Al on Fe, steel and Cu.
Hot dipping
spirit varnish
5
264 A homogeneous colloidal dispersion solution of natural resins in oil is
known as
265 A mechanical dispersion of one or more pigment in a vehicle is known
as
266 A solid substance which forms a paint when mixed with drying oil is
known as
267 Al is _________ than Zn.
5
268 Al will corrode faster when it is in contact with
Cu
5
269 Aluminium oxide film is
Stable-nonporous
5
270
5
271 Asbestos in paints are added as
extenders
5
272 Best method for applying metal coatings on fabricated structures is
metal spraying
5
273 Chemical formula of Rust is
Fe2O3.xH2O
5
274 Coating applied must be chemically __________ to the environment.
Inert
5
5
5
Anodic reaction involves dissolution of metal as corresponding
metallic ions with liberation of _________.
5
275 Coating of Zn, Al and Cd on steel are _________ , because their
electrode potentials are lower.
276 Corrosion process is nothing but ________.
5
277 Driers in paints act as
5
278 During electro-chemical corrosion, if the medium is acidic
5
279 During galvanising, the surface of molten zinc is covered with NH4Cl
5
Applied Chemistry MCQ
varnishes
Paint
Pigments
More anodic
Free electron
Anodic
Oxidation
oxygen carriers
pigment carriers &
oxidizers
hydrogen is
evolved at the
cathode
to prevent
oxidation of Zn
Page No. 10
5
280 Electrochemical corrosion takes place on
Anodic area
5
281 Evolution of hydrogen type corrosion occurs in _______ environment.
Acidic
5
282 Extenders in paints
All of the above
5
283 Fe or steel is ____ with respect to copper.
Anodic
5
284 Fe will corrode faster when it is in contact with
Cu
5
285 Film forming constituent of paint is
drying oil
5
286 Galvanised sheets cannot be used for making
cooking utensils
5
287 Galvanising is the method of applying metal coating by
Hot dipping
5
288 Gold metal forms ______________ type of oxide film.
Unstable
5
289
5
290 In differential aeration corrosion, poor oxygenated parts are
Anodic
5
291 In differential aeration, _______________ part of metal gets corroded
less oxygenated
5
292 In galvanic cell action mode of corrosion, which metal gets protected
one that becomes
the cathode
5
293 In galvanic series, a metal high in series is more _________.
Anodic
5
294 In galvanised sheets of iron, if the Zn coating breaks, ________
corrodes.
Iron
5
295 In galvanising, Zn protects iron from corrosion as
5
296 In Paints, driers are
5
297 In sherardizing, an alloy of ____________ is formed at the surface.
Zn and Fe
5
298 In tinned sheets of iron, if the tin coating breaks,
5
299 In tinning, Sn protects iron from corrosion as
5
300 In tinning, the role of molten flux of zinc chloride is
Iron gets corroded
faster
it is less electropositive than iron
to act as an
adherent
5
301 In waterline corrosion highly oxygenated parts acts as
Cathodic
5
302 Lithium metal forms ______________ type of oxide film.
Stable-porous
5
303 Lower is the pH, ________________ is the corrosion.
Greater
5
304 More active metal used in sacrificial anodic protection method is
known as
Sacrificial anode
5
305 Oil pipelines, if they are leaking undergo corrosion at the joints due to
5
306 Paint is a
5
307 Paint is a mechanical dispersion of
pigments in vehicle
5
308 Parts above and closely adjacent to waterline are _____________.
Cathodic
If the volume of oxide layer formed on the metal surface does not
cover the metal surface completely, the film formed is
Applied Chemistry MCQ
porous
it is more electropositive than iron
oxygen carrier
catalysts
Differential
aeration
mechanical
dispersion
Page No. 11
5
309 Platinum metal forms ______________ type of oxide film.
Unstable
5
310 Potassium metal forms ______________ type of oxide film.
Stable-porous
5
311 Rate of corrosion due to oxygen decreases if the oxide film formed is
Stable-nonporous
5
312 Reddish scale of iron oxide has molecular formula:
Fe3O4
5
313 Rusting of fencing wire under joints is an example of
galvanic cell action
mode of corrosion
5
314 Sherardizing is the method of applying metal coating by
Cementation
5
315 Sherardizing process is carried out in
rotating closed
drums
5
316 Silver metal forms ______________ type of oxide film.
Unstable
5
317 The method to coat odd-shaped iron articles with Zn is known as
Sherardizing
5
318 The process of applying metal coatings such that surface alloying takes
place is known as
319 The process of covering iron/ steel sheets with thin coat of Sn is called
5
320 The process of covering iron/ steel sheets with thin coat of Zn is called
Galvanising
5
321 The rusting of iron is catalyzed by which of the following?
H+
5
322 Tin metal forms ______________ type of oxide film.
Stable-nonporous
5
323 Tinning is the method of applying metal coating by
Hot dipping
5
324 Uneven surfaces of the metals undergo corrosion at the troughs due to
Differential
aeration
5
325 Varnish is a
colloidal dispersion
5
326 Varnishes ______________________________.
5
327 Waterline corrosion is common in ships due to
produces a
transparent film
Differential
aeration
Fe undergoes
corrosion
Fe undergoes
corrosion
5
5
5
5
5
5
5
5
5
5
328 When Fe and Cu are in contact in presence of conducting medium,
which of the following is true?
329 When Fe and Sn are in contact in presence of conducting medium,
which of the following is true?
330 When in contact with Cu, which of the following metals will corrode
faster?
331 When in contact with Cu, which of the following metals will corrode
faster?
332 When in contact with Cu, which of the following metals will corrode
faster?
333 When in contact with Cu, which of the following metals will corrode
faster?
334 When underground iron pipelines are connected to Mg-bars
335 When Zn and Cu are in contact in presence of conducting medium,
which of the following is true?
336 When Zn and Sn are in contact in presence of conducting medium,
which of the following is true?
Applied Chemistry MCQ
Cementation
Tinning
Zn
Fe
Mg
Ni
Mg becomes
sacrificial anode
Zn becomes anode
Zn undergoes
corrosion
Page No. 12
5
337 Which of the following gases accelerates rusting of iron?
All of above
5
338 Which of the following is false about thinners in paints?
5
339 Which of the following is false about varnishes?
it is an oxygen
carrier
produces a nontransparent film
5
340 Which of the following is not a function of the drying oil?
5
341 Which of the following is true about driers in paints?
5
342 Zn and Sn are used as coating metals in hot dipping method because
5
343 Zn is more ________ than Fe.
Electropositive
5
344 Zn will corrode faster when it is in contact with
Cu
Enhancing colour
accelerates the
drying by oxidation
they have low
melting point
6
"The lowest temperature at which the oil gives enough vapour which
345 gives a momentary flash of light when a flame is applied to it" is
known as
"The lowest temperature at which the oil gives enough vapours which
346 catch fire and burn continuously at least for 5 seconds when a flame is
applied to it" is known as
347 ______________ are semi-solid lubricants.
6
348 ______________ should be < 0.1 for a good lubricant.
Acidity Number
6
349 ______________ should be low for a good lubricant.
Viscosity index
6
350 A good lubricant should have ____________volatility
Low
6
351 Acidity Number of lubricants is also known as
Neutralization
number
6
352 Animal and vegetable oils possess:
Good oiliness
Pensky Marten
Apparatus
6
353 Apparatus used to determine flash and fire points of lubricating oil is
known as
354 Example of mineral / petroleum oil is or are:
6
355 Extreme pressure lubrication involves
chemical
adsorption
6
356 Graphite is _________ lubricant.
Solid
6
6
6
Flash point
Fire point
Greases
Oleic acid
6
357 Important extreme pressure additives contains functional group from
following:
358 Lubricant used for machinery like lathes, concrete mixtures etc. are
6
359 Lubricant used in fluid film lubrication should have
low viscosity
6
360 Lubricants are added to reduce
frictional resistance
6
361 Lubricants used for IC engine cylinders are
mineral oils with
additives
6
362 Lubricants used for light cutting tools are
oil emulsions
6
363 Lubricants used for steam engine cylinders are
6
364 Lubricants used for steam engine cylinders should have
mineral oils with
additives
Metal wetting
quality
6
Applied Chemistry MCQ
All of above
solid lubricants
Page No. 13
6
365 Lubricating oil should possess acid value
6
366 Lubrication process in which additives are added to the lubricants is
6
367 Lubrication process involved in delicate instruments is
6
368 Lubrication process involved in sewing machine is
6
369 Lubrication process involved in watches is
6
370 Name the type of lubrication in case of delicate instruments
6
371 Name the type of lubrication in case of Guns
6
372 Name the type of lubrication in case of scientific instruments
6
373 Name the type of lubrication in case of sewing machine
6
374 Name the type of lubrication in case of watches
6
375
Physical adsorption of lubricants takes place in _______________.
Less than 0.1
Extreme-Pressure
Lubrication
Fluid-Film
Lubrication
Fluid-Film
Lubrication
Fluid-Film
Lubrication
Fluid film
lubrication
Fluid film
lubrication
Fluid film
lubrication
Fluid film
lubrication
Fluid film
lubrication
boundary
lubrication.
6
376 Special additives added to mineral oils are known as
Extreme pressure
additives
6
377 Temperature at which the liquid ceases to flow on cooling is said to be
Pour point
6
378 Temperature at which the oil becomes hazy in appearance is said to be
Cloud point
6
379
The force in dynes required to move 1 sq. cm of a liquid over another
surface with a velocity of 1 cm/sec. is known as
viscosity
6
380 The measure of internal resistance to the flow of the fluid is said to be
viscosity
6
381 The presence of lubricant between the moving parts reduces
All of the above
6
6
382 The process of reducing frictional resistance between moving surfaces
is
383 The tendency to vapourise with increase in temperature is said to be
Lubrication
Volatility
Boundary
Lubrication
6
384 The type of lubrication used when the speed is low and the load is high
is
385 The very important property of lubricants for boundary lubrication is
6
386 Unit of viscosity is
Poise
6
387 Viscosities of lubricating oil can be measured by
All of the above
6
388 Viscosity index is
6
6
389 What type of lubrication is used in delicate machines like watches,
sewing machines, etc.?
390 What type of oil is suitable for thick film lubrication?
6
391 Which have the maximum viscosity?
6
Applied Chemistry MCQ
oiliness
rate of change of
viscosity with
temperature
Fluid film
lubrication
Hydrocarbon oil
Coconut Oil
Page No. 14
6
6
6
7
392 Which of the following is true in case of lubricant?
393 Which type of lubrication is used when the pressure is high and speed
is low.
394 Which type of lubrication is used when the pressure, temperature and
speed is very high?
395 ____________ plastics are insoluble in organic solvents?
7
_______________ polymers have strong inter-molecular bonds.
396
7
________________ are insoluble in organic solvents?
397
7
398 ________________ are prepared by condensation polymerization.
7
399 ________________ have weak inter-molecular bonds.
7
_________________ are soluble in organic solvents.
400
prevents wastage of
energy
Boundary
lubrication
Extreme Pressure
lubrication
Thermosetting
Nylon 6 : 6,
Bakelite, Phenol
formaldehyde, Urea
formaldehyde
Nylon 6 : 6,
Bakelite, Phenol
formaldehyde, Urea
formaldehyde
Bakelite, phenol
formaldehyde, urea
formaldehyde
Teflon, PVC,
Polyethene,
Polystyrene
Teflon, Polyvinyl
chloride,
Polyethene,
Polystyrene
Teflon, PVC,
Polyethene,
Polystyrene
Teflon, PVC,
Polyethene,
Polystyrene
7
401 _________________ polymers have linear structure.
7
402 __________________ are prepared by addition polymerization.
7
403 Bakelite is a _____________ plastic.
thermosetting
7
404 Buna-S is ______________ rubber.
thermoset
7
405 During compounding of plastic, asbestos is added as
filler
7
406 During compounding of plastic, camphor is added as
plasticizer
7
407 During compounding of plastic, catalysts added accelerate
polymerisation
7
408 During compounding of plastic, catalysts are added as
accelerator
7
409 During compounding of plastic, pigments added
impart colour
7
410 During compounding of plastic, plasticizers are added
to increase
plasticity
7
411 Elastomer, pigments and catalysts are components of
rubber
7
412 Elastomer, pigments and vulcanizing agents are components of
rubber
7
7
413 Material which undergo large elongation at relatively low stress is
known as
414 Name the property of rubber due to which it is used for coating wires
and cables.
Applied Chemistry MCQ
rubber
Bad conductor of
Electricity
Page No. 15
7
415 Name the property of rubber due to which it is used in making
conveyor belts.
416 Name the property of rubber due to which it is used in making soles of
shoes.
417 Name the property of rubber due to which it is used in making soles of
shoes.
418 Name the property of rubber due to which it is used in making tubes of
bicycle tyres.
419 Natural rubber is a polymer of
7
420 Natural rubber is obtained from a milky emulsion known as
latex
7
421 Nylon is a _____________ plastic.
thermosetting
7
422 Plasticizers, resins, pigments and catalysts are components of
plastic
7
423 Plastics are organic material. (TRUE/ FALSE)
True
7
424 Plastics are used in making window screens for automobiles because
it has optical clarity
7
425 Polystyrene is a _____________ plastic.
thermoplastic
7
426 Polythene is a _____________ plastic.
thermoplastic
7
427 Polyvinyl chloride is a _____________ plastic.
thermoplastic
7
7
7
7
Abrasion resistance
Abrasion resistance
Bad conductor of
heat
Elasticity
isoprene
7
428 Synthetic high molecular weight polymer which can be moulded into
desired shape is known as
429 The linkage of many monomers together is known as
7
430 The repeat unit of a polymer is_____________
Monomer
7
431 The term PVC used in the plastic industry stands for
polyvinyl chloride
7
432 Which of the following has strong inter-molecular bonds?
7
433 Which of the following has weak inter-molecular bonds?
Thermosetting
plastic
Thermosoftening
plastic
7
Applied Chemistry MCQ
Plastic
polymer
Page No. 16