NCERT solutions Chemistry Class 11 Part 1 chapter 6 Thermodynamics

Choose the correct answer. A thermodynamic state function is a quantity

(i) used to determine heat changes

(ii) whose value is independent of path

(iii) used to determine pressure-volume work

(iv) whose value depends on temperature only.

For the process to occur under adiabatic conditions, the correct condition is:

(i) ΔT = 0

(ii) Δp = 0

(iii) q = 0

(iv) w = 0

The enthalpies of all elements in their standard states are:

(i) unity

(ii) zero

(iii) < 0

(iv) different for each element

ΔU^θof combustion of methane is – X kJ mol^–1. The value of ΔH^θ is

(i) = ΔU^θ

(ii) > ΔU^θ

(iii) < ΔU^θ

(iv) = 0

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 CH_4(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.

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

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?

The reaction of cyanamide, NH₂CN_(s),with dioxygen was carried out in a bomb calorimeter, and ΔUwas found to be –742.7 kJ mol^–1at 298 K. Calculate enthalpy change for the reaction at 298 K.

`NH_2 CN(g) + 3/2 O_2(g) -> N_2(g) + CO_2(g) + H_2O(1)`

Calculate the number of kJ of heat necessary to raise the temperature of 60.0 g of aluminium from 35°C to 55°C. Molar heat capacity of Al is 24 J mol^–1 K^–1.

Calculate the enthalpy change on freezing of 1.0 mol of water at 10.0°C to ice at –10.0°C. Δ_fusH = 6.03 kJ mol^–1 at 0°C.

C_p[H₂O(l)] = 75.3 J mol^–1 K^–1

C_p[H₂O(s)] = 36.8 J mol^–1 K^–1

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.

Enthalpies of formation of CO_(g), CO_2(g), N₂O_(g) and N₂O_4(g) are –110 kJ mol^–1, – 393 kJ mol^–1, 81 kJ mol^–1 and 9.7 kJ mol^–1 respectively. Find the value of Δ_rH for the reaction:

N₂O_4(g) + 3CO_(g) → N₂O_(g) + 3CO_2(g)

Given

`N_(2(g)) + 3H_(2(g)) -> 2NH_(3(g))`; Δ_rH^θ = –92.4 kJ mol^–1

What is the standard enthalpy of formation of NH₃ gas?

Calculate the standard enthalpy of formation of CH₃OH_(l) from the following data:

CH₃OH_(l) + `3/2` O_2(g) →CO_2(g) + 2H₂O_(l) ; Δ_rH^θ = –726 kJ mol^–1

C_(g) + O_2(g) →CO_2(g) ; Δ_cH^θ = –393 kJ mol^–1

H_2(g) +`1/2` O_2(g) → H₂O_(l) ; Δ_fH^θ = –286 kJ mol^–1.

Calculate the enthalpy change for the process

CCl_4(g) → C_(g) + 4Cl_(g)

and calculate bond enthalpy of C–Cl in CCl_4(g).

Δ_vapH^θ (CCl₄) = 30.5 kJ mol^–1.

Δ_fH^θ (CCl₄) = –135.5 kJ mol^–1.

Δ_aH^θ (C) = 715.0 kJ mol^–1, where Δ_aH^θ is enthalpy of atomisation

Δ_aH^θ (Cl₂) = 242 kJ mol^–1

For an isolated system, ΔU = 0, what will be ΔS?

For the reaction at 298 K,

2A + B → C

ΔH = 400 kJ mol^–1 and ΔS = 0.2 kJ K^–1 mol^–1

At what temperature will the reaction become spontaneous considering ΔH and ΔS to be constant over the temperature range?

For the reaction,2Cl_(g) → Cl_2(g), what are the signs of ΔH and ΔS?

For the reaction

2A_(g) + B_(g) → 2D_(g)

ΔU^θ = –10.5 kJ and ΔS^θ= –44.1 JK^–1.

Calculate ΔG^θ for the reaction, and predict whether the reaction may occur spontaneously.

The equilibrium constant for a reaction is 10. What will be the value of ΔG^θ? R = 8.314 JK^–1 mol^–1,T = 300 K.

Comment on the thermodynamic stability of NO_(g), given

`1/2` N_2(g) + `1/2` O_2(g) → NO_(g) ; Δ_rH^θ = 90 kJ mol^–1

NO_(g) +`1/2` O_2(g) → NO_2(g) : Δ_rH^θ= –74 kJ mol^–1

Calculate the entropy change in surroundings when 1.00 mol of H₂O_(l) is formed under standard conditions. Δ_fH^θ = –286 kJ mol^–1.