PUNAKHA HIGHER SECONDARY SCHOOL
CLASS 12
TRIAL RUN 2013
FULL MARKS:100
CHEMISTRY
Paper I
(Theory)
Three Hours
--------------------------------------------------------------------------------Answer all questions in Part I and nine questions from Part II.
All working, including rough work should be done on the same sheet as, and adjacent to the rest of the
answer.
The intended marks for questions are given in brackets [].
In working out problems, use the following data:
Gas constant R=0.0821 lit atm K-1 mol-1, 8.314 JK-1mol-1
-------------------------------------------------------------------------------------------Part I
(40 marks)
Answer all questions
Question 1
a)
Correct the following statements.
i.
[6]
The nature of molal elevation constant is independent of the nature of nonvolatile solute
and solvent.
ii.
The emission of a β particle from a radioactive element increases the mass number by one.
iii.
Grignard reagents contain carbon – carbon sigma bonds.
iv.
Negative value of ∆H is the sole criterion for spontaneity of a process.
v.
The weight of metal deposited during electrolysis of the metal salt depends on the
concentration of electrolyte.
vi.
Ethanol and dimethyl ether exhibits chain isomerism.
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b) Each question is provided with four alternatives A, B, C and D. Choose the correct
alternative and write it in your answer sheet.
i.
ii.
iii.
iv.
v.
vi.
vii.
[10]
Which one of the following is used to make non -stick cookware?
A
PVC
B
polystyrene
C
polyethylene terephthalate
D
polytetrafluoro ethylene
NH3 and BF3 form an adduct readily due to the formation of
A
coordinate bond
B
ionic bond
C
hydrogen bond
D
covalent bond
The formation of cyanohydrin compound from ketone is an example of
A
nucleophilic substitution
B
electrophilic substitution
C
nucleophilic addition
D
electrophilic addition
In a plot of log k versus 1/T, the slope is
A
- Ea /2.303
B
Ea/2.303R
C
Ea/ 2.303
D
- Ea/ 2.303R
When glucose is treated with sodium amalgam, it is reduced to
A
gluconic acid B
saccharic acid
C
sorbitol
osazone
D
When nitrobenzene is chlorinated, the product formed is
A
m-nitrochlorobenzene
B
o-nitrochlorobenzene
C
m-chloronitrobenzene
D
o-p-nitrochlorobenzene
When the pH of a solution is increased from 3 to 6, its H+ ion, the concentration
will be
viii.
A
increased by 1000 times
B
decreased by 1000 times
C
doubled
D
reduced by half
The action of HNO2 on C2H5NH2 gives
A
ethanol
B
ethane
C
nitroethane
D
ethyl nitrite
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ix.
Mac Arthur Forrest process is used for the extraction of
x.
A
zinc
B
lead
C
copper
D
silver
Diketo piperazine is formed as a result of heat on
c)
A
urea
B
glycine
C
acetone
D
ethanamine
Fill in the blanks by choosing the words from the brackets.
[4]
(1 and 3, size, Ag, number, lateral, 1and 2, solute particles, 24, Zn, solvent particles,
Cu, linear,)
i.
Colligative properties of a solution depend upon the ---------- of the --------.
ii.
Zinc can displace ------ from CuSO4 solution, but cannot displace ------ form
MgSO4 solution.
iii.
Alums contain metals of valency of ------- and generally have ------- molecules of
water of crystallization.
iv.
d)
π bonds are formed by -----------overlap of ---------- orbitals.
Match the items in column A with those of B and re write the correct matching the
correct matching pairs in your answer sheet.
[5]
Column A
Column B
i) Nernst equation
a) water
ii) Lactic acid
b) constant pressure
iii) amphiprotic solvent
c) ammonia
iv) Lewis base
d) optical isomers
v) Isochoric process
e) electrochemical cells
f) constant volume
g) functional isomers
.
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e)
Answer the following questions in brief.
i) Metals show metallic lusture. Explain.
[1]
ii) What is the oxidation state and coordination number of central metal in the coordinate
complex [Co(NH3)4SO4] NO3
[1]
iii) Compare SN1 and SN2 reactions.
iv)
[2]
Write the equation for the reaction of formaldehyde with ammonia and name
the product.
[1]
The enthalpy change for the transition of liquid water to steam ∆Hvap is 41.03 KJ
vi)
mol-1 at 373 K. calculate the entropy change for the process.
[2]
vii)
Give one example of homogenously catalyzed reaction and name the catalyst.
[1]
viii)
How is urea detected by Biuret test?
[1]
ix)
Give the balanced equation for the preparation of soap? Name the process and the
and the byproduct formed.
[2]
x)
Represent the zwitter ion of glycine.
[1]
xi)
Write the full form of TEL and give one industrial use of it.
[1]
xii) Phenol is ortho and para directing molecule. Support the statement with the help
of suitable resonating structures.
[2]
Part II (28 marks)
Section A
Answer any four questions.
Question 2.
a) A solution is prepared by dissolving 1.25 g of a nonvolatile solute in 20 g of water.
If the molar mass of solute is 116.25 g mol-1, determine the freezing point of the solution.
Given Kf = 1.86 K Kg mol-1
[3]
b) Differentiate between cationic and anionic hydrolysis. What type of hydrolysis is observed in
the hydrolysis of NH4Cl.
[2]
c) Water, ammonia and hydrogen fluoride have common bonding features. Identify the feature and
arrange them in order of increasing boiling point.
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[2]
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Question 3.
a) A sample of wooden archeological species gave 9 counts against 15 counts given by the fresh
wood. Calculate the age of the wooden sample. t ½ of C-14 is 5770 years.
[3]
b) Explain how does a catalyst increase the rate of a reaction?
c)
[2]
Predict whether an aqueous solution of stannous chloride can be stored in a silver
vessel or not. Given Eo Sn2+/Sn = - 0.137 V, Eo Ag+/Ag = 0.80 V
[2]
Question 4
a)
A study of chemical kinetics of the reaction A + B
products, gave the following data
at 25oC.
[3]
Experiment
[A] molL-1
[B] molL-1
1
1.0
0.15
4.2 x 10-6
2
2.0
0.15
8.4 x 10 -6
3
1.0
0.20
5.6 x10-6
i)
The order of reaction with respect to A
ii)
The order of reaction with respect to B
iii)
The rate law.
b)
Initial rate mol L-1 s-1
AB is a weak electrolyte. A solution of one mole of AB is contained in V litres. If a
degree of dissociation of AB into A+ and B-, deduce Ostwald’s dilution formula
c)
is the
[2]
Draw molecular orbital diagram for N2 molecule and find its
i.
Bond order
ii.
Magnetic property.
[2]
Question 5
a) A decinormal solution sodium acetate when placed between two electrodes each having a cross
section of 2.25cm2 and separated by a distance of 0.72cm, has a resistance of 52.4 ohms.
Calculate the specific conductance and the equivalent conductance of the solution.
[3]
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b) The molecular weight determined by elevation of boiling point method for NaCl is half its
actual molecular weight. Give reason.
[2]
c) Compare the shape of BeCl2 and H2O using VSEPRT.
[2]
d) Question 6
a) The phase diagram of ice-water-water vapour system is shown below. Study the same and
answer the questions that follow.
C
[3]
A
liquid
vapour
vapour pressure
O
solid
B
temperature
i)
Give the mathematical expression for the Gibbs phase rule.
ii)
Identify the curves OA, OB and OC.
iii)
What is the name given to point O?
iv)
Find the degree of freedom along curve OC.
b) Complete the following nuclear equations:
14
i.
C
6
ii.
27
Al
13
14
7
[1]
N + ------
4
+ 2 He
30
15
P + --------
c) The solubility product of CaF2 in water is 8 x 10-10. Calculate its solubility in grams/litre in
0.1M NaF solution.(At wt Ca = 40. F=19)
[2]
d) Give the IUPAC names of the following coordination compounds.
i.
[Cu(NH3)4]SO4
ii.
K3[Al(C2O4)3]
[1]
Question 7
a) With reference to diamond answer the following
i.
[3]
Lattice structure
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ii.
Coordination number
iii.
Hybridization
iv.
Conductance
b) How is the colloidal solution of As2S3 (Arsenous sulphide) prepared?
c) Give two points of difference between Frenkel and Schottky defects
[2]
[2]
Section B
(18 marks)
Answer any three questions.
Question 8
a) Give an account of the extraction of tin, from tinstone.
[3]
b) Classify the following reactions as per the type of reagent and type of reaction.
C6H5Cl + H+
i. C6H6 + Cl+
H
C
ii. H3C
CH3 + OH-
alc
H2C
C
H
CH3 + H2O + Br-
Br
iii. H2C
iv.
BrCH2 CH2Br
+ Br2
CH2
uv light
CH4 + Cl2
CH3Cl + HCl
c) State second law of thermodynamics in terms of entropy of the universe
[2]
[1]
Question 9
a) For the reaction NH4Cl (s)
NH3 (g) + HCl(g) at 25o C, enthalpy change ∆H = 177k J mol-1
and the entropy change ∆S = 285 kJmol-1 K-1. Calculate the free enery change ∆G and predict
whether the reaction is spontaneous or not.
[3]
b) Write short notes on
i.
Inductive effect
ii.
Thermal death
iii.
Application of coordination compounds
[3]
Question 10
a)
i.
ii.
Give the mathematical expression for the first law of thermodynamics.
[1]
The enthalpy of formation of ethane at 25o C and constant pressure is -110.46kJ
Calculate the value of change in internal energy at constant volume.
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2C + 3H2
C2H
c) Give an outline for the preparation of iodine from sea weeds.
[2]
[3]
Question 11
a) Give balanced chemical equations for the preparations for the following compounds
b)
i.
Silicon carbide
ii.
Bleaching powder.
Write balanced chemical equations for the following:
i.
H2S is bubbled into ferric chloride solution.
ii.
Na2SO3 is reacted with H2O2
c) What are silicones? Give the structure of cross linked silicones.
[2]
[2]
[2]
Section C
(14 marks)
Answer any two questions.
Question 12
a) Write the balanced chemical equations for the following reactions:
i.
Diethyl ether with hot HI
ii.
Acetaldehyde with ammoniacal silver nitrate
iii.
Ethyl acetate with PCl5
iv.
Acetone with iodine and KOH.
[4]
b) What would you observe when
i.
Urea is treated with HNO3
ii.
Ethylamine reacts with chloroform and KOH
iii.
Glucose is heated with excess of phenylhydrazine
[3]
Question 13
a) Complete and balance the following equations:
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i. CH3CHO + NH2OH
........
ii C6H5CONH2 + Br2 + NaOH
............
[2]
b) Perform the following conversions:
i.
Vinyl chloride to PVC
ii.
Phenol to picric acid
iii.
Acetyl chloride to acetaldehyde
iv.
Differentiate between thermoplastic and thermosetting polymers with example. [2]
[3]
Question 14
a) An organic compound A on treatment with ethanol forms carboxylic acid B and compound C.
hydrolysis of C gives B and D. Oxidation of D with KMnO4 gives compound B. Compound B
on dry distillation with Ca(OH)2 gives E with molecular formula C3H6O. E does not reduce
Tollen’s reagent.Identify compounds A,B,C,D and E.
[4]
b) Discuss the isomerism exhibited by lactic acid.
[2]
c) Give the preparation of Dacron.
[1]
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