Thermodynamics · Question 47

Bond dissociation enthalpies of H2, Cl2 and HCl are 434, 242 and 431 kJ mol-1 respectively. Enthalpy of formation of HCl is

1. -93 kJ mol-1
2. 245 kJ mol-1
3. 93 kJ mol-1
4. -245 kJ mol-1

For the gas phase reaction, PCl5(g) PCl3(g) + Cl2(g) which of the following conditions are correct?

1. < 0 and < 0
2. > 0 and < 0
3. = 0 and < 0
4. > 0 and > 0

Which of the following are not state functions? (I) q + w (II) q (III) w (IV) H - TS

1. (I), (II) and (III)
2. (II) and (III)
3. (I) and (IV)
4. (II), (III) and (IV)

Consider the following reactions: (i) H+(aq) + OH-(aq) H2O(l), H = -X1 kJ mol-1 (ii) H2(g) + 12O2(g) H2O(l), H = -X2 kJ mol-1 (iii) CO2(g) + H2(g) CO(g) + H2O(l), H = -X3 kJ mol-1 (iv) C2H2(g) + 52O2(g) 2CO2(g) + H2O(l), H = +X4 kJ mol-1 Enthalpy of formation of H2O(l) is

1. +X3 kJ mol-1
2. -X4 kJ mol-1
3. +X1 kJ mol-1
4. -X2 kJ mol-1

Given that bond energies of H-H and Cl-Cl are 430 kJ mol-1 and 240 kJ mol-1 respectively and Hf for HCl is -90 kJ mol-1, bond enthalpy of HCl is

1. 380 kJ mol-1
2. 425 kJ mol-1
3. 245 kJ mol-1
4. 290 kJ mol-1

Identify the correct statement for change of Gibbs energy for a system ( Gsystem) at constant temperature and pressure.

1. If Gsystem < 0, the process is not spontaneous.
2. If Gsystem > 0, the process is spontaneous.
3. If Gsystem = 0, the system has attained equilibrium.
4. If Gsystem = 0, the system is still moving in a particular direction.

Assume each reaction is carried out in an open container. For which reaction will H = E?

1. 2CO(g) + O2(g) 2CO2(g)
2. H2(g) + Br2(g) 2HBr(g)
3. C(s) + 2H2O(g) 2H2(g) + CO2(g)
4. PCl5(g) PCl3(g) + Cl2(g)

The enthalpy and entropy change for the reaction: Br2(l) + Cl2(g) 2BrCl(g) are 30 kJ mol-1 and 105 J K-1 mol-1 respectively. The temperature at which the reaction will be in equilibrium is

1. 300 K
2. 285.7 K
3. 273 K
4. 450 K

The enthalpy of hydrogenation of cyclohexene is -119.5 kJ mol-1. If resonance energy of benzene is -150.4 kJ mol-1, its enthalpy of hydrogenation would be

1. -358.5 kJ mol-1
2. -508.9 kJ mol-1
3. -208.1 kJ mol-1
4. -269.9 kJ mol-1

Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction ?

1. Exothermic and increasing disorder
2. Exothermic and decreasing disorder
3. Endothermic and increasing disorder
4. Endothermic and decreasing disorder