Thermodynamics

The formation enthalpies, Hf for H(g) and O(g) are 220.0 and 250.0 kJ mol-1, respectively, at 298.15 K, and Hf for H2O(g) is -242.0 kJ mol-1 at the same temperature. The average bond enthalpy of the O-H bond in water at 298.15 K is kJ mol-1 (nearest integer).

[figure] An ideal gas undergoes a cyclic transformation starting from the point A and coming back to the same point by tracing the path A→B→C→D→A as shown in the three cases above. Choose the correct option regarding U :

1. U(Case-III) > U(Case-II) > U(Case-I)
2. U(Case-I) > U(Case-II) > U(Case-III)
3. U(Case-I) = U(Case-II) = U(Case-III)
4. U(Case-I) > U(Case-III) > U(Case-II)

Consider the following data: Heat of formation of CO2(g) = -393.5 kJ mol-1 Heat of formation of H2O(l) = -286.0 kJ mol-1 Heat of combustion of benzene = -3267.0 kJ mol-1 The heat of formation of benzene is kJ mol-1. (Nearest integer)

Let us consider an endothermic reaction which is non-spontaneous at the freezing point of water. However, the reaction is spontaneous at boiling point of water. Choose the correct option.

1. Both and are (-ve)
2. is (+ve) but is (-ve)
3. is (-ve) but is (+ve)
4. Both and are (+ve)

Standard entropies of X2, Y2 and XY5 are 70, 50 and 110 J K-1 mol-1 respectively. The temperature in Kelvin at which the reaction 12X2 + 52Y2 XY5 H = -35 kJ mol-1 will be at equilibrium is (Nearest integer)

S(g)+ 32O2(g) SO3(g)+2x kcal SO2(g)+ 12O2(g) SO3(g)+y kcal The heat of formation of SO2(g) is given by :

1. 2x+y kcal
2. 2xy kcal
3. y-2x kcal
4. x+y kcal

Which of the following mixing of 1 M base and 1 M acid leads to the largest increase in temperature?

1. 50 mL HCl and 20 mL NaOH
2. 30 mL HCl and 30 mL NaOH
3. 45 mL CH3COOH and 25 mL NaOH
4. 30 mL CH3COOH and 30 mL NaOH

Ice at -5 C is heated to become vapor with temperature of 110 C at atmospheric pressure. The entropy change associated with this process can be obtained from

1. 268 K273 K Cp,m dT + Hm, fusionTf + Hm, vaporisationTb + 273 K373 K Cp,m dT + 373 K383 K Cp,m dT
2. 268 K383 K Cp dT + Hmelting273 + Hboiling373
3. 268 K383 K Cp dT + qrevT
4. 268 K273 K Cp,mT dT + Hm, fusionTf + Hm, vaporisationTb + 273 K373 K Cp,m dTT + 373 K383 K Cp,m dTT

The standard enthalpy and standard entropy of decomposition of N2O4 to NO2 are 55.0 kJ mol-1 and 175.0 J/K/mol respectively. The standard free energy change for this reaction at 25 in J mol-1 is (Nearest integer)

The effect of temperature on spontaneity of reactions are represented as : [figure] The incorrect combinations are :

1. A and C only
2. B and D only
3. A and D only
4. B and C only