ISC Chemistry 2014 Class-12 Previous Year Question Paper

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ISC Chemistry 2014 Class-12 Previous Year Question Paper Solved


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Part – I

Part – II Section – A

Part – II Section – B

Part – II Section – C


Maximum Marks: 70
Time allowed: 3 hours

  • Answer all questions in Part I and six questions from Part II, choosing two questions from Section A, two from Section B and two from Section C.
  • 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 or parts of questions are given in brackets [ ].
  • Balanced equations must be given wherever possible and diagrams where they are helpful.
  • When solving numerical problems, all essential working must be shown.
  • In working out problems use the following data:
    Gas constant R = 1.987 cal deg-1 mol-1 = 8.314 JK-1 mol-1 = 0.0821 dm3 atm K-1 mol-1. 1L atm = 1 dm3 atm = 101.3 J.
    1 Faraday = 96500 Coulombs, Avogadro’s number = 6.023 × 1023

Part – I (20 Marks)
(Answer all questions)

ISC Chemistry 2014 Class-12 Previous Year Question Paper Solved

Question 1.
(a) Fill in the blanks by choosing the appropriate word/words from those given in the brackets: [5]
(increases, formic acid, decreases, less, zero, small, paired, atoms, unpaired, ions, pentagonal bipyramidal, electrical, more, ethylamine, molecules, propanoic acid, methylamine, chemical.)
(i) An electrochemical cell converts ……… energy to ……….. energy.
(ii) The crystal of graphite is made-up of ………. while that of sodium chloride is made-up of ………..
(iii) Ethyl isocyanide, on hydrolysis with dilute sulphuric acid, gives ……… and ………
(iv) The molar conductance of a solution ………… with dilution, while its specific conductance ……….. with dilution.
(v) The Van’t Hoff factor of the acetic acid solution is …………… than one and the value of a normal colligative property is ……… than the observed colligative property of this solution.

(b) Complete the following statements by selecting the correct alternative from the choices given: [5] (i) Of the following terms used for denoting the concentration of a solution, the one which does not get affected by temperature is:
(1) Molarity
(2) Molality
(3) Normality
(4) Formality

(ii) The solubility of calcium hydroxide is s mol litre-1. The solubility product under the same condition will be:
(1) 4s3
(2) 2s3
(3) 2s2
(4) s3

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(iii) A current liberates 0.50 g of hydrogen in 2 hours. The weight of copper (at. wt. = 63.5) deposited at the same time by the same current through copper sulphate solution is:
(1) 63.5 g
(2) 31.8 g
(3) 15.9 g
(4) 15.5 g

(iv) Natural rubber is a:
(1) Polyester
(2) Polyamide
(3) Polyisoprene
(4) Polysaccharide

(v) Among the following halogens, the one which does not form an oxyacid is:
(1) Fluorine
(2) Chlorine
(3) Bromine
(4) Iodine

(c) Answer the following questions: [5]
(i) What is the [OH] concentration of an acid whose pH is 5 at 25°C?
(ii) What happens when a nickel rod is dipped into a copper sulphate solution? Justify your answer.
\left[\mathrm{E}_{\mathrm{Ni}^{2+} / \mathrm{Ni}}^{\circ}=-0.25 \mathrm{V} \text { and } \mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.34 \mathrm{V}\right]
(iii) Write the equation for the preparation of acetanilide from aniline.
(iv) Define Raoult’s law for the elevation of the boiling point of a solution.
(v) An ionic compound is made-up of A cations and B anions. If A cations are present at the alternate comers and B anion is present on the body of the diagonal, what is the formula of the ionic compound? [5]

(d) Match the following:

(i) Molal depression constant (a) Infinite dilution
(ii) Acetaldehyde (b) mol L-1 sec-1
(iii) Rate of reaction (c) Iodoform
(iv) Optical activity (d) K kg mol-1
(v) Kohlrausch’s law (e) Lactic acid

Answer 1:
(a)

(i) chemical, electrical
(ii) atoms, ions
(iii) ethylamine, formic acid
(iv) increases, decreases
(v) more, less

(b)

(i) (2) Molality
(ii) (1) 453
(iii) (3) 15.9 g
(iv) (3) Polyisoprene
(v)   (1) Fluorine
ISC Chemistry Question Paper 2015 Solved for Class 12 Q1
(iv) According to Raoult’s law: ‘Elevation of a boiling point of a solution is directly proportional to the lowering in vapour pressure caused by the number of particles of solute present in the solution’.
(v) The formula of an ionic compound is A+B or AB.
(d)

(i) (d)
(ii) (c)
(iii) (b)
(iv) (e)


Part – II (50 Marks)

A nswer six questions choosing two from Section A, two from Section B and two from Section C.

Section – A
(Answer any two questions)

ISC Chemistry 2014 Class-12 Previous Year Question Paper Solved

Question 2.

(a)

(i) What will be the vapour pressure of a solution containing 5 moles of sucrose (C12H22O11) in 1 kg of water, if the vapour pressure of pure water is 4.57 mm of Hg? [C = 12, H = 1, O = 16] [3] (ii) A 2 molal solution of sodium chloride in water causes an elevation in the boiling point of water by 1.88 K. What is the value of Vant Hoff factor? What does it signify? [Kb = 0.52 K kg mol-1] [2] (b)

(i) Write the mathematical expression relating the variation of the rate constant of a reaction with temperature. [4] (ii) How can you graphically find the activation energy of the reaction from the above expression?
(iii) The slope of the line in the graph of log k (k = rate constant) versus \frac { 1 }{ T } is -5841. Calculate the activation energy of the reaction.
(c) Define the Frenkel defect in a solid crystal. [1] Answer 2:
(a)

(i) According to Raoult’s law, for a solution containing non-volatile solute
ISC Chemistry Question Paper 2015 Solved for Class 12 Q2
This value of ‘i’ signifies that when 1 mole of NaCl is dissolved in water it dissociates to give 1.8076 moles of particles in the solution.

(b)

(i) The mathematical expression of the Arrhenius equation:
k=\mathrm{A} e^{-\mathrm{E}_{a} / \mathrm{RT}}
where k is rate constant of the given reaction
A is another constant called frequency factor
Ea is activation energy
R is gas constant
T is the temperature in Kelvin.
(ii) Finding activation energy graphically: Taking a log of Arrhenius equation
ISC Chemistry Question Paper 2015 Solved for Class 12 Q2.1
ISC Chemistry Question Paper 2015 Solved for Class 12 Q2.2
It is an equation for a straight line (y = mx + C)
Therefore, on plotting a graph between different values of log10k and \frac { 1 }{ T } at different temperature, a straight line as shown in fig. is obtained and slope of line is equal to -\frac{\mathrm{E}_{a}}{2.303 \mathrm{R}}
Thus, by knowing slope, we can calculated Ea
(iii) \text { Slope }=-\frac{\mathrm{E}_{a}}{2.303 \mathrm{R}}
or -Ea = -5841 × 2.303 × 8.314
Ea = 111838.45 J mol-1 = 111.838 kJ mol-1

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