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## ISC Chemistry 2017 Class-12 Previous Year Question Paper Solved

-: Select Options :-

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 × 102

Part – I (20 Marks)

### ISC Chemistry 2017 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] (iodoform, acetaldehyde, positive, greater, acidic, acetone, disaccharide, negative, increases, glucose, decreases, chloroform, polysaccharide, lactose, lesser, basic, cationic hydrolysis, anionic hydrolysis)
(i) Calcium acetate on heating gives ………. which gives ……… on heating with iodine and sodium hydroxide solution.
(ii) On dilution of a solution, its specific conductance ……….. while its equivalent conductance ……….
(iii) Sucrose is a ………… and yields upon hydrolysis, a mixture of ………. and fructose.
(iv) More ………. the standard reduction potential of a substance, the ……… is its ability to displace hydrogen from acids.
(v) An aqueous solution of CH3COONa is ………. due to …………

(b) Complete the following statements by selecting the correct alternative from the choices given: [5] (i) In a face-centred cubic lattice, atom (A) occupies the comer positions and atom (B) occupies the face centre positions. If one atom of (B) is missing from one of the face-centred points, the formula of the compound is:
(1) A2B5
(2) A2B3
(3) AB2
(4) A2B

(ii) The half-life period of a first-order reaction is 20 minutes. The time required for the concentration of the reactant to change from 0.16 M to 0.02 M is:
(1) 80 minutes
(2) 60 minutes
(3) 40 minutes
(4) 20 minutes

(iii) For a spontaneous reaction ΔG° and E° cell will be respectively:
(1) -ve and +ve
(2) +ve and -ve
(3) +ve and +ve
(4) -ve and -ve

(iv) The conjugate acid of $\mathrm{HPO}_{4}^{2-}$ is:
(1) H3PO3
(2) H3PO4
(3) $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$
(4) $\mathrm{PO}_{4}^{3-}$

(v) The polymer formed by the condensation of hexamethylenediamine and adipic acid is:
(1) Teflon
(2) Bakelite
(3) Dacron
(4) Nylon-66

(c) Answer the following questions: [5]
(i) Why the freezing point depression (ΔTf) of 0.4 M NaCl solution is nearly twice than that of 0.4 M glucose solution?
(ii) Identify the order of reaction from each of the following units of rate constant (k):
(a) mol L-1 sec-1
(b) mol-1 L sec-1
(iii) Specific conductivity of 0.20 M solution of KCl at 298 K is 0.025 S cm-1. Calculate its molar conductivity.
(iv) Name the order of reaction which proceeds with a uniform rate throughout.
(v) What are the products formed when phenol and nitrobenzene are treated separately with a mixture of concentrated sulphuric acid and concentrated nitric acid?
(d) Match the following: [5]

 (i) Diazotisation (a) Bakelite (ii) Argentite (b) Nernst equation (iii) Thermosetting plastics (c) Aniline (iv) Electrochemical cell (d) Ethylenediamine (v) Bidentate ligand (e) Froth floatation process

(a)

(i) acetone, iodoform
(ii) decreases, increases
(iii) disaccharide, glucose
(iv) negative, greater
(v) basic, anionic hydrolysis

(b)

(i) (1)
(ii) (2)
(iii) (1)
(iv) (3)
(v) (4)

(c)

(i) This is because Van’t Hoff factor for NaCl is 2 and for glucose, it is 1.
(ii) (a) – Zero
(b) – Two
\begin{aligned}(\text {iii}) &=\frac{k \times 1000}{\text { Molarity }} \\ &=\frac{0.025 \times 1000}{0.20} \\ \Lambda_{m} &=125 \mathrm{S} \mathrm{cm}^{2} \mathrm{mol}^{-1} \end{aligned}
(iv) Zero
(v) 2, 4, 6 – Trinitrophenol
m – Dinitrobenzene

(d)

(i) – (c)
(ii) – (e)
(iii) – (a)
(iv) – (b)
(v) – (d)

Part – II (50 Marks)

Section – A

### ISC Chemistry 2017 Class-12 Previous Year Question Paper Solved

Question 2.
(a)

(i) Determine the freezing point of a solution containing 0.625 g of glucose (C6H12O6) dissolved in 102.8 g of water. [2] (Freezing point of water = 273 K, Kf for water = 1.87 K kg mol-1, at. wt. C = 12, H = 1, O = 16)
(ii) A 0.15 M aqueous solution of KCl exerts an osmotic pressure of 6.8 atm at 310 K. [2] Calculate the degree of dissociation of KCl. (R = 0.0821 Lit. atm K-1 mol-1).
(iii) A solution containing 8.44 g of sucrose in 100 g of water has a vapour pressure 4.56 mm of Hg at 273 K. If the vapour pressure of pure water is 4.58 mm of Hg at the same temperature, calculate the molecular weight of sucrose. [1] (b)

(i) When ammonium chloride and ammonium hydroxide are added to a solution containing both Al3+ and Ca2+ ions, which ion is precipitated first and why? [2] (ii) A solution of potassium chloride has no effect on litmus whereas, a solution of zinc chloride turns the blue litmus red. Give a reason. [2] (c) How many sodium ions and chloride ions are present in a unit cell of sodium chloride crystal? [1] Answer 2:

(b)

(i) Al3+ ions are precipitated first as Al(OH)3 because Ksp for Al(OH)3 is lower than that of Ca(OH)2.
(ii) This is because KCl does not undergo hydrolysis in water and the aqueous solution is neutral whereas ZnCl2 undergoes hydrolysis in water to give an acidic solution which turns blue litmus solution red.
$\begin{array}{rl}{\mathrm{Zn}^{2+}+2 \mathrm{C} \mathrm{I}^{-}+2 \mathrm{H}_{2} \mathrm{O}} & {\rightleftharpoons \mathrm{Zn}(\mathrm{OH})_{2}+2 \mathrm{H}^{+}+2 \mathrm{Cl}} \\ {\mathrm{or}} & {\mathrm{Zn}^{2+}+2 \mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{Zn}(\mathrm{OH})_{2}+2 \mathrm{H}^{+}}\end{array}$

(c) Number of Na+ ions = 4
Number of Cl– ions = 4

Question 3.
(a)

(i) Lead sulphide has a face-centred cubic crystal structure. If the edge length of the unit cell of lead sulphide is 495 pm, calculate the density of the crystal. [1] (at. wt. of Pb = 207, S = 32)
(ii) For the reaction: $2 \mathrm{H}_{2}+2 \mathrm{NO} \rightleftharpoons 2 \mathrm{H}_{2} \mathrm{O}+\mathrm{N}_{2}$, the following rate data was obtained: [3]
Calculate the following:
(1) The overall order of a reaction.
(2) The rate law.
(3) The value of rate constant (k).
(b)

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