PART II : CHEMISTRY

SECTION 1 (Maximum Marks: 21)

• This section contains SEVEN questions

• Each question has FOUR options [A], [B], [C] and [D]. ONLY ONE of these four options is correct

1. Pure water freezes at 273 K and 1 bar. The addition of 34.5 g of ethanol to 500 g of water changes the freezing point of the solution. Use the freezing point depression constant of water as 2 K kg mol⁻¹. The figures shown below represent plots of vapour pressure (V.P.) versus temperature (T). [molecular weight of ethanol is 46 g mol⁻¹]

Among the following, the option representing change in the freezing point is

(A)

(B)

(C)

(D)

Answer: (C)

2. For the following cell,

Zn(s)|ZnSO₄(aq)||CuSO₄(aq)|Cu(S)

when the concentration of Zn²⁺ is 10 times the concentration of Cu²⁺, the expression for ∆G (in J mol⁻¹) is

[F is Faraday constant, R is gas constant; T is temperature; E°(cell) = 1.1V]

(A) 1.1 F

(B) 2.303 RT – 2.2F

(D) −2.2F

Answer: (B)

3. The standard state Gibbs free energies of formation of C(graphite) and C(diamond) at T = 298 K are

∆_fG°[C(graphite)]= 0 kJ mol⁻¹

∆_fG° [C(diamond)] = 2.9 kJ mol⁻¹

The standard state means that the pressure should be 1 bar, and substance should be pure at a given temperature. The conversion of graphite [C(graphite) ] to diamond [C(diamond) ] reduces its volume by 2 × 10⁻⁶ m³ mol⁻¹. If C(graphite) is converted to C(diamond) isothermally at T = 298 K, the pressure at which C(graphite) is in equilibrium with C(diamond) , is

[Useful information: 1 J = 1 kg m² s⁻²; Pa = 1 kg m⁻¹ s⁻²; 1 bar = 10⁵ Pa]

(A) 14501 bar

(B) 58001 bar

(D) 29001 bar

Answer: (A)

4. Which of the following combination will produce H₂ gas?

(A) Fe metal and conc. HNO₃

(B) Cu metal and conc. HNO₃

(D) Au metal and NaCN(aq) in the presence of air

Answer: (C)

5. The order of the oxidation state of the phosphorus atom in H₃PO₂, H₃PO₄, H₃PO₃, and H₄P₂O₆ is

(A) H₃PO₃ > H₃PO₂ > H₃PO₄ > H₄P₂O₆

(B) H₃PO₄ > H₃PO₂ > H₃PO₃ > H₄P₂O₆

(D) H₃PO₂ > H₃PO₃ > H₄P₂O₆ > H₃PO₄

Answer: (C)

6. The major product of the following reaction is

(A)

(B)

(C)

(D)

Answer: (C)

7. The order of basicity among the following compounds is

(A) II > I > IV > III

(B) IV > II > III > I

(D) I > IV > III > II

Answer: (C)

SECTION 2 (Maximum Marks: 28)

• This section contains SEVEN questions

• Each question has FOUR options [A], [B], [C] and [D]. ONE OR MORE THAN ONE of these four options is(are) correct

8. The correct statement(s) about surface properties is(are)

(A) Adsorption is accompanied by decrease in enthalpy and decrease in entropy of the system

(B) The critical temperatures of ethane and nitrogen are 563 K and 126 K, respectively. The adsorption of ethane will be more than that of nitrogen on same amount of activated charcoal at a given temperature

(D) Brownian motion of colloidal particles does not depend on the size of the particles but depends on viscosity of the solution

Answer: (A, B)

9. For a reaction taking place in a container in equilibrium with its surroundings, the effect of temperature on its equilibrium constant K in terms of change in entropy is described by

(A) With increase in temperature, the value of K for exothermic reaction decreases because the entropy change of the system is positive

(B) With increase in temperature, the value of K for endothermic reaction increases because unfavourable change in entropy of the surroundings decreases

(C) With increase in temperature, the value of K for endothermic reaction increases because the entropy change of the system is negative

(D) With increase in temperature, the value of K for exothermic reaction decreases because favourable change in entropy of the surroundings decreases

Answer: (B, D)

10. In a bimolecular reaction, the steric factor P was experimentally determined to be 4.5. The correct option(s) among the following is(are)

(A) The activation energy of the reaction is unaffected by the value of the steric factor

(B) Experimentally determined value of frequency factor is higher than that predicted by Arrhenius equation

(D) The value of frequency factor predicted by Arrhenius equation is higher than that determined experimentally

Answer: (A, B)

11. For the following compounds, the correct statement(s) with respect to nucleophilic substitution reactions is(are)

(A) I and III follow S_N1 mechanism

(B) I and II follow S_N2 mechanism

(D) The order of reactivity for I, III and IV is: IV > I > III

Answer: (A, B, C, D)

12. Among the following, the correct statement(s) is(are)

(A) Al(CH₃)₃ has the three-centre two-electron bonds in its dimeric structure

(B) BH₃ has the three-centre two-electron bonds in its dimeric structure

(D) The Lewis acidity of BCl₃ is greater than that of AlCl₃

Answer: (A, B, D)

13. The option(s) with only amphoteric oxides is(are)

(A) Cr₂O₃, BeO, SnO, SnO₂

(B) Cr₂O₃, CrO, SnO, PbO

(D) ZnO, Al₂O₃, PbO, PbO₂

Answer: (A, D)

14. 32 Compounds P and R upon ozonolysis produce Q and S, respectively. The molecular formula of Q and S is C₈H₈ Q undergoes Cannizzaro reaction but not haloform reaction, whereas S undergoes haloform reaction but not Cannizzaro reaction.

The option(s) with suitable combination of P and R, respectively, is(are)

(A)

(B)

(C)

(D)

Answer: (A, B)

SECTION 3 (Maximum Marks: 12)

• This section contains TWO paragraphs

• Based on each paragraph, there are TWO questions

• Each question has FOUR options [A], [B], [C], and [D]. ONLY ONE of these four options is correct

PARAGRAPH 1

Upon heating KClO₃ in the presence of catalytic amount of MnO₂, a gas W is formed. Excess amount of W reacts with white phosphorus to give X. The reaction of X with pure HNO₃ gives Y and Z.

15. W and X are, respectively

(A) O₃ and P₄O₆

(B) O₂ and P₄O₆

(D) O₃ and P₄O₆

Answer: (C)

16. Y and Z are, respectively

(A) N₂O₃ and H₃PO₄

(B) N₂O₅ and HPO₃

(D) N₂O₄ and H₃PO₃

Answer: (B)

PARAGRAPH 2

The reaction of compound P with CH3MgBr (excess) in (C₂H₅)₂O followed by addition of H₂O gives Q. The compound Q on treatment with H₂SO₄ at 0°C gives R. The reaction of R with CH₃COCl in the presence of anhydrous AlCl₃ in CH₂Cl₂ followed by treatment with H₂O produces compound S. [Et in compound P is ethyl group]