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# NCERT solutions for Class 11 Chemistry chapter 6 - Thermodynamics

## Chapter 6: Thermodynamics

#### Chapter 6: Thermodynamics solutions [Pages 182 - 184]

Q 1 | Page 182

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.

Q 2 | Page 182

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

(i) Δ= 0

(ii) Δ= 0

(iii) = 0

(iv) w = 0

Q 3 | Page 182

The enthalpies of all elements in their standard states are:

(i) unity

(ii) zero

(iii) < 0

(iv) different for each element

Q 4 | Page 182

ΔUθof combustion of methane is – X kJ mol–1. The value of ΔHθ is

(i) = ΔUθ

(ii) > ΔUθ

(iii) < ΔUθ

(iv) = 0

Q 5 | Page 182

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.

Q 6 | Page 182

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

Q 7 | Page 182

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?

Q 8 | Page 182

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)

Q 9 | Page 183

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.

Q 10 | Page 183

Calculate the enthalpy change on freezing of 1.0 mol of water at 10.0°C to ice at –10.0°C. Δfus= 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

Q 11 | Page 183

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.

Q 12 | Page 183

Enthalpies of formation of CO(g), CO2(g), N2O(gand N2O4(gare –110 kJ mol–1, – 393 kJ mol–1, 81 kJ mol–1 and 9.7 kJ mol–1 respectively. Find the value of Δrfor the reaction:

N2O4(g) + 3CO(g) → N2O(g) + 3CO2(g)

Q 13 | Page 183

Given

N_(2(g)) + 3H_(2(g)) -> 2NH_(3(g)); ΔrHθ = –92.4 kJ mol–1

What is the standard enthalpy of formation of NH3 gas?

Q 14 | Page 183

Calculate the standard enthalpy of formation of CH3OH(l) from the following data:

CH3OH(l) + 3/2 O2(g) →CO2(g) + 2H2O(l) ; ΔrHθ = –726 kJ mol–1

C(g) + O2(g) →CO2(g) ; ΔcHθ = –393 kJ mol–1

H2(g) +1/2 O2(g) → H2O(l) ; ΔfHθ = –286 kJ mol–1.

Q 15 | Page 183

Calculate the enthalpy change for the process

CCl4(g) → C(g) + 4Cl(g)

and calculate bond enthalpy of C–Cl in CCl4(g).

ΔvapHθ (CCl4) = 30.5 kJ mol–1.

ΔfHθ (CCl4) = –135.5 kJ mol–1.

ΔaHθ (C) = 715.0 kJ mol–1, where ΔaHθ is enthalpy of atomisation

ΔaHθ (Cl2) = 242 kJ mol–1

Q 16 | Page 183

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

Q 17 | Page 183

For the reaction at 298 K,

2A + B → C

Δ= 400 kJ mol–1 and Δ= 0.2 kJ K–1 mol–1

At what temperature will the reaction become spontaneous considering Δand Δto be constant over the temperature range?

Q 18 | Page 183

For the reaction,2Cl(g) → Cl2(g), what are the signs of Δand ΔS?

Q 19 | Page 183

For the reaction

2A(g) + B(g) → 2D(g)

ΔUθ = –10.5 kJ and ΔSθ= –44.1 JK–1.

Calculate ΔGθ for the reaction, and predict whether the reaction may occur spontaneously.

Q 20 | Page 184

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

Q 21 | Page 184

Comment on the thermodynamic stability of NO(g), given

1/2 N2(g+ 1/2 O2(g→ NO(g) ; ΔrHθ = 90 kJ mol–1

NO(g) +1/2 O2(g→ NO2(g: ΔrHθ= –74 kJ mol–1

Q 22 | Page 184

Calculate the entropy change in surroundings when 1.00 mol of H2O(l) is formed under standard conditions. ΔfHθ = –286 kJ mol–1.

## NCERT solutions for Class 11 Chemistry chapter 6 - Thermodynamics

NCERT solutions for Class 11 Chemistry chapter 6 (Thermodynamics) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Chemistry Textbook for Class 11 solutions in a manner that help students grasp basic concepts better and faster.

Further, we at shaalaa.com are providing such solutions so that students can prepare for written exams. NCERT textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 11 Chemistry chapter 6 Thermodynamics are Thermodynamic Terms, The State of the System, The Internal Energy as a State Function - Work, The Internal Energy as a State Function - Heat, The Internal Energy as a State Function - The General Case, Work, Enthalpy, H - A Useful New State Function, Enthalpy, H - Extensive and Intensive Properties, Enthalpy, H - Heat Capacity, Enthalpy, H - The Relationship Between Cp and Cv for an Ideal Gas, Measurement of ∆U and ∆H Calorimetry - ∆U Measurements, Measurement of ∆U and ∆H Calorimetry - ∆H Measurements, Standard Enthalpy of Reactions, Enthalpy Changes During Phase Transformations, Standard Enthalpy of Formation, Thermochemical Equations, Hess’ Law of Constant Heat Summation, Standard Enthalpy of Combustion, Enthalpy of Atomization, Bond Enthalpy, Enthalpy of Solution, Lattice Enthalpy, Is Decrease in Enthalpy a Criterion for Spontaneity, Entropy and Spontaneity, Gibbs Energy and Spontaneity, Gibbs Energy Change and Equilibrium.

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