Class XII Chemistry Board paper ICSE
(i)What is the equation for the action of heat on calcium nitrate ?
Ans- 2Ca(NO3)2-----------> 2CaO + 4 NO2 + O2
2(40 + 28 + 96) 2(40+16) 4(14 + 32) 2(16)
(328g)----------------(112g)------184g-------32g
2 moles of Calcium nitrate produces 4 moles of NO2
1 mole calcium nitrate produces how many moles of NO2?
= 4/2 = 2 moles of NO2
(ii) What volume of O2 at STP will be produced on heating 65.6g of Ca(NO3)2?
Ans- 328g of Ca(NO3)2 produces 32g of O2
1g of Ca(NO3)2 produce how much of o2?
= 32/328
65.6g of Ca(NO3)2 produce how much of O2?
= 32/328 x 656/10 = 6.4g of oxygen
32g of O2 occupy 24 liters of volume
6.4g of O2 occupy how many liters?
= 22.4/32 x 64/10 = 4.48 liters.
(iii) Find out the mass of CaO formed when 65.6g of Ca(NO)3 is heated?
Ans- 328g of Ca(NO3)2 forms 112g of CaO
65.6g of Ca(NO3)2 produces how many grams of CaO?
= 112/328 x 656/10 = 22.4g of CaO
(iv) Find out the mass of CaO formed when 65.6g of Ca(NO3)2 is heated?
Ans- 5 moles of gaseous product is formed by 2 moles of Ca(NO3)2
1 mole of Ca(NO3)2 weighs = 164g
Then, 2 moles of Ca(NO3)2 weighs = 2 x 164 = 328g
(v) Find out the mass of calcium nitrate required to produce 44.8 liters of NO2 at S.T.P
(Relative molecular mass of Ca(NO3)2 = 164 and CaO = 56)
Ans- According to the given equation
4 x 22.4 liters of NO2 will be formed by 2 x 164g of calcium nitrate
44.8 liters of NO2 will be formed by how many grams of calcium nitrate?
NO2= 2 x 164/4 x 22.4 x 44.8 = 164g of calcium nitrate.
(Note: To do this type of lengthy sums you must have a clear understanding of basic concepts
of the topic)
(c) Name the organic compound formed by each of the following reactions:
(i) CH3 COONa + NaOH ----------> (above the arrow Ca, below the arrow heat)
Ans. Methane
(ii) CaC2 + H2O------>
Ans. Acetylene (ethyne)
(iii) C2H5Br + KOH(alc.)----->
Ans. Ethylene (ethene)
(iv) C2H5OH + CH3COOH------->
Ans. Ethyl alcohol (ethanol)
(v) C2H5OH +CH3COOH-----> (above the arrow conc.H2SO4 and below the arrow heat)
Ans. Ester (Ethyl acetate)
(d) Identify the following substances:
(i) An acidic gas which give dense white fumes with NH3
Ans. HCl gas
(ii) An alklane which can also be called a green house gas.
Ans. Methane (CH4)
(iii) A solid which can be kept in the open, forms a solution after sometime
Ans. Iron (III) chloride (a delequescence substance)
(iv) An alloy used in electrical fittings
Ans. Nickel steel
(v) A metal which gives hydrogen gas on reacting with both dilute acid and alkali
Ans. Zinc
(e) Write equations for the following reactions:
(i) Aluminium oxide and sodium hydroxide
Ans. Al2O3 + 2 NaOH -----------> 2NaAlO2 + H2O
(ii) Zinc and dilute sulphuric acid
Ans. Zn + H2SO4(dil.) ----------> ZnSO4 + H2
(iii) Nitrogen dioxide and water
Ans. 2NO2 + H2O----------> HNO3 + HNO2
(iv) Concentrated sulphuric acid and sugar
Ans. C12H22O11-----------> 12C + 11 H2O (Above the arrow conc.H2SO4-dehydrating
agent)
(v) Copper with concentrated nitric acid
Ans. Cu + 4HNO3-----------> CU(NO3)2 + 2H2O + 2NO2
(f)Name the following:
(i) Second member of alkene series
Ans. Propene
(ii) First member of alkane series
Ans. Methane
(iii) Third member of aldehyde series
Ans. Propanal
(iv) Second member of carboxylic acid
Ans. Ethanoic acid
(v) Fourth member of alcohol series
Ans. Butanol
(g) Write IUPAC names of the following:
(i) Methanol
(ii) Propanone
(iii) Butan-2-ol
(iv) Ethoxyethane
(v) 2,2-dimethyl propane
Section II (40 Marks)
Question 2
(a) The following questions refer to periodic table:
(i) Name the second last element of periodic table
Ans. Chlorine
(ii) How many elements are in the second period?
Ans. Eight
(iii) Name the element which has the highest electron affinity
Ans. Chlorine
(iv) Name the element which has the highest electronegativity
Ans. Fluorine
(v) Name the metal which may be placed on group 1 but is not a metal
Ans. Hydrogen
(b) Fill in the blanks by using correct options:
(i) Metals have ----- ionization potential.(low/high)
Ans. low
(ii) Group 18 elements have ------ valence electrons (4/80 with the exception of -----(He/Ne)
with ----- electrons(2/8) in valence shell.
Ans. 8, He, 2
(iii) Group 2 elements are called ------ metals (alkali/alkaline earth)
Ans. alkaline earth
Question 3
(a) Draw the different isomers having the following molecular formula:
(i) C5H12
Practice pentane isomers from text book.
(ii) C4H8(position)
Practice But-1-ene and But-2-ene diagrams from text book.
(b) What is denatured alcohol?
Ans. Denatured alcohol is prepared by adding substances like methyl alcohol or pyridine to
ethyl alcohol. Denatured alcohol is poisonous due to the presence of methyl alcohol and it is
undrinkable.
(c) Give two important uses of ethanol.
(i) It is a good solvent for resins and gums.
(ii) It is used in thermometers because of its low freezing point.
(iii) It is used in the manufacture of chemicals like dyes, perfumes, antiseptics etc.
(d) Write equations for:
(i) Preparation of ethanol by hydration of C2H4
Ans. C2H4 + H2O-------> C2H5OH (above arrow H+)
(ii) Preparation of acetic acid from ethanol
Ans. C2H5OH + O2---------> CH3COOOH + H2O (above arrow 300 degrees celsius, below
the arrow Pt.)
Question 4
(a) Name the method by which following compounds can be prepared: Select the appropriate
method from the following list-Neutralization; direct combination; precipitation; metal+aciduse a method only once.
(i) Sodium sulphate
Ans. Neutralization
(ii) Silver chloride
Ans. Precipitation
(iii) Iron sulphide
Ans. Direct combination
(b) How will you distinguish between the following pairs of compounds using NH4OH
(i) Copper (II) sulphate and Iron (II) sulphate
Ans. By adding NH4OH to CuSO4, a pale blue ppt. of Cu(OH)2 is formed and it is insoluble
in excess NH4OH and produce inky blue solution.
By adding NH4OH to CuSo4, a dirty green precipitate of Fe(OH)2 is formed and it is
insoluble in excess of NH4OH.
(ii) Zinc nitrate and lead nitrate
Ans. By adding NH4OH to Zinc nitrate drop by drop, a white gelatinous ppt. is formed and it
is soluble in excess of NH4OH.
By adding NH4OH to lead nitrate, a white ppt. is formed which is in soluble in excess of
NH4OH.
(iii) Iron (II) sulphate and iron (III) sulphate
Ans. By adding NH4OH to FeSO4 solution, a dirty green ppt. of FeOH2 is formed which is
insoluble in excess of NH4OH.
When NH4OH is added to FeSO4 solution, a reddish brown ppt. of FeOH3 is formed and it is
insoluble in water.
(c) Name:
(i) A greenish yellow gas with pungent smell
Ans. Chlorine
(ii) An oxide which is yellow when hot and white when cold
Ans. Zinc oxide
(iii) A chemical used to deplete ozone layer
Ans. Chlorofluorocarbons
(iv) A crystalline salt without water of crystallization
Ans. Common salt- NaCl
Question 5
(a) Name one:
(i) metal liquid at room temperature
Ans. Mercury
(ii) non-metal which is a conductor of electricity
Ans. Graphite
(iii) neutral oxide
Ans. H2O
(iv) metallic oxide which cannot be reduced by hydrogen
Ans. Zinc oxide
(v) non-metal which has luster
Ans. Iodine
(b) (i) Name the chief ore of aluminum
Ans. Bauxite
(ii) Name the process used to concentrate the above mentioned ore.
Ans. Bayer's process
(iii) Why alumina is added to cryolite in the electrolytic reduction of aluminum?
Ans. To reduce the fusion temperature from 2050 degrees celsius to 950 degrees celsius.
(iv) Give cathode and anode reactions involved in extraction of aluminum from its above
mentioned ore.
Ans. Cathode: 4Al+3 + 12 e- -------> 4 Al
Anode: 6O2- + 12e- -------> 6(O)
3(O) + 3(O) --------> 3O2
2C + 2O2 -------> 2CO2
(v) Name the process used for the concentration of zinc blende
Ans. Froth floatation process
Question 6
(a) Draw a neat well labelled diagram for the silver plating on an iron spoon.
Practice the diagram from text book.
(b) Copy and complete the following table related to electrolysis.
Ans. 1. Product at cathode: Copper
Product at anode: Cu+2
2. Product at cathode: Lead
Product at anode: Bromine
(c) Classify the following as oxidation and reduction reaction, also complete the reaction.
(i) Cu------> Cu+2
Ans. Cu - 2e- -----> Cu+2 (oxidation)
(ii)Fe+3--------> Fe+2
Ans. Fe+3 + e- ------> Fe+2 (reduction)
(iii) Cl- -------> Cl
Ans. Cl- - e- -------> Cl (oxidation)
Question 7
(a) A compound has the following percentage composition by mass:
Carbon-54.55%, Hydrogen-9.09% and oxygen- 36.26%. Its vapor density is 44. Find the
empirical formula and molecular formula of the compound.(H=1; C=12; O=16)
Ans.Carbon -------4.55% ------12 --------54.55/12 = 4.54--- 4.54/2.26 = 2
Hydrogen ------- 9.09%--------1--------9.09/1 = 9.09-----9.09/2.26 = 4
Oxygen-------36.26%--------16--------36.26/16 = 2.26-----2.26/2.26 = 1
Empirical formula of the compound: C2 H4 O
Vapor density = 44
Molecular Mass = n = (VD x 2) 44 x 2 = n x 44
44 x 2 = n(44)
n=2
Molecular formula = C4H8O2
(B) Give the electron dot structure of the following:
(i) NH3 (ii) CH4 (iii) H3O+
Draw and practice the pictures from text book.
(c) Compare the properties of covalent and electrovalent compounds on the following points.
Solubility:
Covalent: These compounds are insoluble in water and soluble in organic solvent.
Electrovalent: These compounds are soluble in water but insoluble in organic solvents.
Structure:
Covalent: Structure of covalent compounds are not much stable;
usually they are amorphous solids or liquids.
Electrovalent: Structure is stable; usually crystalline solids.