1. Equilibrium constant for the following reaction at 298 K
2 NH3 (g) + CO2 (g) 
NH2CONH2 (aq.) + H2O (l) is
(∆rG° = −13.6 KJ mol−1)
1) 2.38 2) 2.4 × 102 3) 13.6 4) 4.76
Ans: (2)
2. The reaction is spontaneous at all the temperatures is
1) ∆H = -ve , ∆S = -ve, ∆G = -ve
2) ∆H = +ve, ∆S = +ve, ∆G = -ve
3) ∆H = -ve, ∆S = +ve, ∆G = -ve
4) ∆H = -ve, ∆S = -ve, ∆G = +ve
Ans: (3)
Explanation: If ∆H = -ve, ∆S = +ve, ∆G = -ve, the reaction is spontaneous at all the temperatures.
3. The correct mathematical relation in terms of ∆G, ∆H and ∆S is
Ans: (4)
4. For an insulated system ∆U = 0. So ∆S will be
1) -ve 2) +ve 3) 0 4) we can’t say
Ans: (2)
Explanation: ∆H = ∆U + ∆ nRT, ∆G = ∆H - T ∆S
∵ ∆U = 0 ∆S will be +ve.
1) The entropy of a pure and perfectly crystalline substance is zero at −273°C.
2) The energy is neither created nor destroyed.
3) Entropy is neither created nor destroyed.
4) Heat can’t flow from colder body to hotter body by its own.
Ans: (1)
Explanation: It is formula for 3rd law of thermodynamics.
6. Incorrect statement among the following is
1) Internal energy is state function.
2) Work is not a state function.
3) Temperature is a path function as well as extensive property.
4) Volume is state function as well as extensive property.
Ans: (3)
Explanation: Temperature is a state function and intensive property.
7. A swimmer coming out from a river is covered with film of water weighing 36 g. The amount of heat given by the sun to evoparate this water at 298 K is
1) 37.56 KJ mol-1 2) 34.46 KJ mol-1 3) 34.46 J mol-1 4) 37.56 J mol-1
Ans: (2)
8. The correct order of standard molar enthalpies of C (graphite), H2 gas, Cl2 gas, Br2 liquid is
1) Br2 (l) > Cl2 (g) > H2 (g) > C (graphite)
2) C (graphite) > H2 (g) > Cl2 (g) > Br2 (l)
3) C (graphite) > Br2 (l) > Cl2 (g) > H2 (g)
4) C (graphite) = H2 (g) = Cl2 (g) = Br2 (l)
Ans: (4)
Explanation: C (graphite), Br2, Cl2 and H2 are in their standard states. So thier standard molar enthalpies are also zero.
9. Entropy decreases in the case of
1) H2 (g) → 2 H (g)
2) 2 NaHCO3 (s) → Na2CO3 (s) + CO2 (g) + H2O (g)
3) A liquid crystallises to a solid
4) Temperature of a crystalline solid is raised from 0 K to 107 K
Ans: (3)
Explanation: After crystallisation, the molecules attain an ordered state and entropy decreases.
10. The bond enthalpy (∆H) of C - Cl in CCl4 is
1) 1304 KJ mol−1 2) 326 KJ mol−1 3) 1302 KJ mol−1 4) 258 KJ mol−1
Ans: (2)
11. The change in internal energy if heat is absorbed and work is done on the system is
1) ∆E = Q + W 2) ∆E = -W - Q
3) ∆E = W - Q 4) ∆E = Q - W
Ans: (1)
Explanation: Q = +ve, W = +ve.
12. 50% of N2O4 dissociates at 333 K. ∆rG° for this change will be (in KJ mol−1)
1) 763.8 2) -76.38 3) -7638 4) -763.8
Ans: (4)
13. The entropy change is positive among the following reactions is
1) 
2) Na+ (g) + Cl− (g) → NaCl (s)
3) NaCl (l) → NaCl (s) 4) H2O (l) → H2O (g)
Ans: (4)
Explanation: Disorderness of gaseous H2O molecules i.e. entropy is more than liquid H2O molecules.
14. The enthalpy of formation of NH3 is -46 KJ mol−1. The enthalpy change for the reaction
2 NH3 (g) → 2 N2 (g) + 3 H2 (g) is
1) 46 KJ mol−1 2) 92 KJ mol−1 3) −92 KJ mol−1 4) −23 KJ mol−1
Ans: (2)
15. In the dissociation of CH4 (g)
1) 3 bonds have equal energy.
2) 2 bonds have equal energy.
3) bond energies are different for all the 4 bonds.
4) bond energies are euqal for all the 4 bonds.
Ans: (3)
Explanation: Bond energies for all the 4 bonds (C − Cl) are different.
16. The heat of combustion of solid benzoic acid at constant volume is -321.3 KJ mol-1 at 300 K. The heat of a combustion at constant pressure is
1) -321.3 - 150 R 2) -321.3 - 300 R 3) -321.3 + 300 R 4) -321.3 + 450 R
Ans: (1)
17. If H+ + OH- → H2O + 57.3 K.J., then the heat of neutralization of 1 gram mole of H2SO4 with NaOH will be
1) 28.7 K.J. 2) 57.3 K.J. 3) 114.6 K.J. 4) 14.3 K.J.
Ans: (3)
Explanation: 1 mole of H2SO4 = 2 equivalents of H2SO4 = 2 moles of H2O = 2 × 57.3 = 114.6 KJ.
18. If one mole of NH3 and 1 mole of HCl are mixed in a closed container to form NH4Cl vapour, then
1) ∆H > ∆U 2) ∆H < ∆U 3) ∆H = ∆U 4) ∆H = ∆U = 0
Ans: (2)
19. Bond dissociation enthalpy of H2, Cl2 and HCl are 434, 242 and 431 K.J. mol-1 respectively. Enthalpy of formation of HCl is
1) 93 KJ mol-1 2) -245 KJ mol-1 3) 245 KJ mol-1 4) -93 KJ mol-1
Ans: (4)
20. The decomposition of lime stone is non spontaneous at 298 K. The ∆H° and ∆S° values for the reaction are 176 KJ and 160 JK-1 mol-1 respectively. At what temperature, the decomposition becomes spontaneous?
1) above 827°C 2) below 500°C 3) at 500°C 4) at 1000° K
Ans: (1)
21. The enthalpy (H) of water, when it is super cooled to -4°C is
1) same as ice at 0°C 2) less than ice at -4°C
3) same as ice at -4°C 4) more than ice at -4°C
Ans: (2)
Explanation: When ice is cooled upto -4°C, heat is released and enthalpy is decreased.
22. The enthalpy and entropy change for the reaction Br2 (l) + Cl2 (g) → 2 BrCl (g) are 30 KJ mol-1 & 105 JK-1 mol-1respectively. The temperature at which the reaction will be in equilibrium is
1) 450 K 2) 300 K 3) 285.7 K 4) 273 K
Ans: (3)
23. When Zn dust is added to aq. solution of CuSO4, 3.175 g of Cu metal and 20 J of heat is evolved. The ∆H for this reaction is
1) 100 J 2) 20 J 3) 200 J 4) 400 J
Ans: (4)
24. 1 mole of perfect gas expands isothermally to 10 times its original volume. The change in entropy is
1) 100 R 2) 2.303 R 3) 10 R 4) 4.606 R
Ans: (2)
25. If the bond enthalpies of H - H, Br - Br and H - Br are 433, 192 and 364 KJ mol−1 respectively, the ∆H° for the reaction
H2 (g) + Br2 (g) → 2 HBr (g) is
1) +261 KJ 2) -261 KJ 3) +103 KJ 4) -103 KJ
Ans: (4)
Explanation: ∆rH
= Σ B.E. of reactants - Σ B.E. of products
= (433 + 192) - 2(364) = −103 KJ.
