Thermodynamics

13. Given N₂(g) + 3H₂(g) → 2NH₃(g); ?_r H^– = -92.4 kJ mol^-1. What is the standard enthalpy of formation of NH₃ gas? 

12. Enthalpies of formation of CO(g), CO₂(g), N₂O(g) and N₂O₄(g) are –110, – 393, 81 and 9.7 kJ mol^–1 respectively. Find the value of Δ_rH for the reaction: N₂O₄(g) + 3CO(g) → N₂O(g) + 3CO₂(g)

11. Enthalpy of combustion of carbon to CO₂ is – 393.5 kJ mol^-1. Calculate the heat released upon formation of 35.2 g of CO₂ from carbon and dioxygen gas.  

10. Calculate the enthalpy change on freezing of 1.0 mol of water at 10.0°C to ice at -10.0°C. A, Δ_fusH = 6.03 KJ mol^-1 at 0°C.

Cp [H₂O(l)] = 75.3 J mol^-1 K^-1;

Cp [H₂O(s)] = 36.8 J mol^-1 K^-1.

9. Calculate the number of KJ of heat necessary to raise the temperature of 60 g of aluminium from 35°C to 55°C. Molar heat capacity of Al is 24 J mol^-1 K^-1.

8. The reaction of cyanamide,NH₂CN(s) with dioxygen was carried out in a bomb calorimeter and ?U was found to be -742,7 KJ^-1  mol^-1 at 298 K. Calculate the enthalpy change for the reaction at 298 K.

NH₂CN (S) + 3/2O₂(g) → N₂(g) + CO₂(g) + H₂O(l)

7.  In a process, 701 J of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?        

6. A reaction, A + B—>C + D + q is found to have a positive entropy change. The reaction will be

(i) Possible at high temperature                               

(ii) Possible only at low temperature

(iii) Not possible at any temperature                         

(iv) Possible at any temperature  

5. The enthalpy of combustion of methane, graphite and dihydrogen at 298 K are -890.3 KJ mol^-1, – 393.5 KJ mol^-1 and – 285.8 KJ mol^-1 respectively. Enthalpy of formation of CH₄(g) will be

(i) – 74.8 KJ mol^-1                                         

(ii) – 52.27 KJ mol^-1

(iii) + 74.8 KJ mol^-1                                 

(iv) + 52.26 KJ mol^-1    

4. ΔU^? of combustion of methane is – X kJ mol^–1. The value of ΔH^? is

(i) = ΔU^?

(ii) > ΔU^?

(iii) < U^?

(iv) = 0