NCERT Solutions for Class 11 Chemistry Chapter 6 Thermodynamics in English Medium based on new edition NCERT Books for session 2022-2023. Get here Class 11 Chemistry Chapter 6 MCQ, extra questions, exercises and intext question-answers.

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Thermodynamics

Thermodynamics is the study of the relations between heat, work, temperature, and energy. The laws of thermodynamics describe how the energy in a system changes and whether the system can perform useful work on its surroundings.

Class 11 Chemistry Chapter 6 MCQ

Q1

Thermodynamics is not concerned about

[A]. Energy changes involved in a chemical reaction.
[B]. The extent to which a chemical reaction proceeds.
[C]. The rate at which a reaction proceeds.
[D]. The feasibility of a chemical reaction.
Q2

Which of the following statements is correct?

[A]. The presence of reacting species in a covered beaker is an example of open system.
[B]. There is an exchange of energy as well as matter between the system and the surroundings in a closed system.
[C]. The presence of reactants in a closed vessel made up of copper is an example of a closed system.
[D]. The presence of reactants in a thermos flask or any other closed insulated vessel is an example of a closed system.
Q3

The state of a gas can be described by quoting the relationship between

[A]. Pressure, volume, temperature
[B]. Temperature, amount, pressure
[C]. Amount, volume, temperature
[D]. Pressure, volume, temperature, amount
Q4

The volume of gas is reduced to half from its original volume. The specific heat will be

[A]. Reduce to half
[B]. Be doubled
[C]. Remain constant
[D]. Increase four times

The System and the Surroundings

A system in thermodynamics refers to that part of universe in which observations are made and remaining universe constitutes the surroundings. The surroundings include everything other than the system. System and the surroundings together constitute the universe.
The universe = The system + The surroundings

Types of the System

There are mainly three type of systems are existing in the universe:

    • 1. Open system
    • 2. Closed system
    • 3. Isolated system

Class 11 Chemistry Chapter 6 Multiple Choice Questions

Q5

The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound

[A]. Is always negative
[B]. Is always positive
[C]. May be positive or negative
[D]. Is never negative
Q6

Enthalpy of sublimation of a substance is equal to

[A]. Enthalpy of fusion + enthalpy of vaporization
[B]. Enthalpy of fusion
[C]. Enthalpy of vaporization
[D]. Twice the enthalpy of vaporization
Q7

Which of the following is not correct?

[A]. ∆G is zero for a reversible reaction
[B]. ∆G is positive for a spontaneous reaction
[C]. ∆G is negative for a spontaneous reaction
[D]. ∆G is positive for a non-spontaneous reaction
Q8

The spontaneity means, having the potential to proceed without the assistance of external agency. The processes which occur spontaneously are

[A]. Flow of heat from colder to warmer body.
[B]. Gas in a container contracting into one corner.
[C]. Gas expanding to fill the available volume.
[D]. Burning carbon in oxygen to give carbon dioxide.

Class 11 Chemistry Chapter 6 Extra Important Questions

The molar enthalpy of vaporization of acetone is less than that of water. Why?

Because of strong hydrogen bonding in water, its enthalpy of vaporization is more = –178.3 kJ mol⁻¹

Given that ∆H= 0 for mixing of two gases. Explain whether the diffusion of these gases into each other in a closed container is a spontaneous process or not?

It is spontaneous process. Although enthalpy change is zero but randomness or disorder (i.e., ∆S) increases. Therefore, in equation
∆G = ∆H – T∆S, the term T∆S will be negative. Hence, ∆G will be negative.

Predict the change in internal energy for an isolated system at constant volume.

For isolated system, there is no transfer of energy as heat or as work. i.e.,
w = 0 and q = 0.
According to the first law of thermodynamics.
∆U = q + w
= 0 + 0 = 0
∴ ∆U = 0

Open System

In an open system, there is exchange of energy and matter between system and surroundings. The presence of reactants in an open beaker is an example of an open system. Here the boundary is an imaginary surface enclosing the beaker and reactants.

Closed system

The system that allows only the transfer of energy in or out of the system but does not allow the transfer of matter is known to be a closed system. For example, a beaker of evaporating water with a closed lid on it allows the transfer of energy to the surroundings but does not allow (matter) water to leave.

Isolated system

An isolated system is a thermodynamic system that cannot exchange either energy or matter outside the boundaries of the system. There are two ways in which this may occur: The system may be so distant from another system that it cannot interact with them.

Work in thermodynamics

In thermodynamics, thermodynamic work is the quantity of energy transferred from one system to another. It is a generalization of the concept of mechanical work in mechanics. In the SI system of measurement, work is measured in joules (symbol: J). The rate at which work is performed is power.

Reversible and Irreversible Processes

A process or change is said to be reversible, if a change is brought out in such a way that the process could, at any moment, be reversed by an infinitesimal change. A reversible process proceeds infinitely slowly by a series of equilibrium states such that system and the surroundings are always in near equilibrium with each other. Processes other than reversible processes are known as irreversible processes.

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