JEE Main > Thermodynamics

Explore popular questions from Thermodynamics for JEE Main. This collection covers Thermodynamics previous year JEE Main questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

Heat given to a body which raises its temperature by {tex} 1 ^ { \circ } \mathrm { C } {/tex} is

A

water equivalent

thermal capacity

C

specific heat

D

temperature gradient.

Explanation

Q 2.    

Correct4

Incorrect-1

Which statement is incorrect?

all reversible cycles have same efficiency

B

reversible cycle has more efficiency than an irreversible one

C

Carnot cycle is a reversible one

D

Carnot cycle has the maximum efficiency in all cycles.

Explanation



Q 3.    

Correct4

Incorrect-1

Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will

A

increase

B

decrease

remain same

D

decrease for some, while increase for others.

Explanation


Q 4.    

Correct4

Incorrect-1

At what temperature is the r.m.s. velocity of a hydrogen molecule equal to that of an oxygen molecule at {tex} 47 ^ { \circ } \mathrm { C } ? {/tex}

A

{tex} 80 \mathrm {\ K } {/tex}

B

{tex} - 73 \mathrm {\ K } {/tex}

C

{tex} 3 \mathrm {\ K } {/tex}

{tex} 20 \mathrm {\ K } {/tex}

Explanation



Q 5.    

Correct4

Incorrect-1

Even Carnot engine cannot give {tex} 100 \% {/tex} efficiency because we cannot

A

prevent radiation

B

find ideal sources

reach absolute zero temperature

D

eliminate friction.

Explanation

Q 6.    

Correct4

Incorrect-1

{tex}1{/tex} mole of a gas with {tex} \gamma = 7 / 5 {/tex} is mixed with {tex}1{/tex} mole of a gas with {tex} \gamma = 5 / 3 , {/tex} then the value of {tex} \gamma {/tex} for the resulting mixture is

A

{tex} 7 / 5 {/tex}

B

{tex} 2 / 5 {/tex}

{tex} 24 / 16 {/tex}

D

{tex} 12 / 7 {/tex}

Explanation



Q 7.    

Correct4

Incorrect-1

"Heat cannot by itself flow from a body at lower temperature to a body at higher temperature" is a statement or consequence of

second law of thermodynamics

B

conservation of momentum

C

conservation of mass

D

first law of thermodynamics.

Explanation

Q 8.    

Correct4

Incorrect-1

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio {tex} C _ { P } / C _ { V } {/tex} for the gas is

A

{tex} 4 / 3 {/tex}

B

{tex}2{/tex}

C

{tex} 5 / 3 {/tex}

{tex} 3 / 2 {/tex}

Explanation


Q 9.    

Correct4

Incorrect-1

Which of the following parameters does not characterize the thermodynamic state of matter?

A

temperature

B

pressure

{tex} \mathrm {work}{/tex}

D

volume.

Explanation

Q 10.    

Correct4

Incorrect-1

A Carnot engine takes {tex} 3 \times 10 ^ { 6 } {/tex} cal of heat from a reservoir at {tex} 627 ^ { \circ } \mathrm { C } , {/tex} and gives it to a sink at {tex} 27 ^ { \circ } \mathrm { C } {/tex}. The work done by the engine is

A

{tex} 4.2 \times 10 ^ { 6 } \mathrm {\ J } {/tex}

{tex} 8.4 \times 10 ^ { 6 } \mathrm {\ J } {/tex}

C

{tex} 16.8 \times 10 ^ { 6 } \mathrm {\ J } {/tex}

D

{tex} \mathrm { zero } {/tex}

Explanation



Q 11.    

Correct4

Incorrect-1

One mole of ideal monoatomic gas {tex} ( \gamma = 5 / 3 ) {/tex} is mixed with one mole of diatomic gas {tex} ( \gamma = 7 / 5 ) {/tex}. What is {tex} \gamma {/tex} for the mixture? {tex} \gamma {/tex} denotes the ratio of specific heat at constant pressure, to that at constant volume.

{tex} 3 / 2 {/tex}

B

{tex} 23 / 15 {/tex}

C

{tex} 35 / 23 {/tex}

D

{tex} 4 / 3 {/tex}

Explanation



Q 12.    

Correct4

Incorrect-1

Which of the following statements is correct for any thermodynamic system?

A

The internal energy changes in all processes.

Internal energy and entropy are state functions.

C

The change in entropy can never be zero.

D

The work done in an adiabatic process is always zero.

Explanation

Q 13.    

Correct4

Incorrect-1

Two thermally insulated vessels {tex}1{/tex} and {tex}2{/tex} are filled with air at temperatures {tex} \left( T _ { 1 } , T _ { 2 } \right) , {/tex} volume {tex} \left( V _ { 1 } , V _ { 2 } \right) {/tex} and pressure {tex} \left( P _ { 1 } , P _ { 2 } \right) {/tex} respectively. If the valve joining the two vessels is opened, the temperature inside the vessel at equilibrium will be

A

{tex} T _ { 1 } + T _ { 2 } {/tex}

B

{tex} \left( T _ { 1 } + T _ { 2 } \right) / 2 {/tex}

{tex} \frac { T _ { 1 } T _ { 2 } \left( P _ { 1 } V _ { 1 } + P _ { 2 } V _ { 2 } \right) } { P _ { 1 } V _ { 1 } T _ { 2 } + P _ { 2 } V _ { 2 } T _ { 1 } } {/tex}

D

{tex} \frac { T _ { 1 } T _ { 2 } \left( P _ { 1 } V _ { 1 } + P _ { 2 } V _ { 2 } \right) } { P _ { 1 } V _ { 1 } T _ { 1 } + P _ { 2 } V _ { 2 } T _ { 2 } } {/tex}

Explanation





Q 14.    

Correct4

Incorrect-1

Which of the following is incorrect regarding the first law of thermodynamics?

A

It introduces the concept of the internal energy

It introduces the concept of entropy

C

It is not applicable to any cyclic process

D

It is a restatement of the principle of conservation of energy

Explanation

Q 15.    

Correct4

Incorrect-1

The temperature- entropy diagram of a reversible engine cycle is given in the figure. efficiency is

{tex} 1 / 3 {/tex}

B

{tex} 2 / 3 {/tex}

C

{tex} 1 / 2 {/tex}

D

{tex} 1 / 4 {/tex}

Explanation



Q 16.    

Correct4

Incorrect-1

A system goes from {tex} A {/tex} to {tex} B {/tex} via two processes I and II as shown in figure. If DU1 and DU2 are the changes in internal energies in the processes I and II respectively, then

A

{tex} \Delta U _ { 2 } > \Delta U _ { 1 } {/tex}

B

{tex} \Delta U _ { 2 } < \Delta U _ { 1 } {/tex}

{tex} \Delta U _ { 1 } = \Delta U _ { 2 } {/tex}

D

relation between {tex} \Delta U _ { 1 } {/tex} and {tex} \Delta U _ { 2 } {/tex} can not be determined

Explanation


Q 17.    

Correct4

Incorrect-1

A gaseous mixture consists of {tex} 16 \mathrm { g } {/tex} of helium and {tex} 16 \mathrm { g } {/tex} of oxygen. The ratio {tex} C _ { P } / C _ { V } {/tex} of the mixture is

A

{tex} 1.4 {/tex}

B

{tex} 1.54 {/tex}

C

{tex} 1.59 {/tex}

{tex} 1.62 {/tex}

Explanation


Q 18.    

Correct4

Incorrect-1

The work of {tex} 146 \mathrm { kJ } {/tex} is performed in order to compress one kilo mole of gas adiabatically and in this process the temperature of the gas increases by {tex} 7 ^ { \circ } \mathrm { C } {/tex}. The gas is {tex} \left( R = 8.3 \mathrm { J } \mathrm { mol } ^ { - 1 } \mathrm { K } ^ { - 1 } \right) {/tex}

A

monoatomic

diatomic

C

triatomic

D

a mixture of monoatomic and diatomic.

Explanation





Q 19.    

Correct4

Incorrect-1

Two rigid boxes containing different ideal gases are placed on a table. Box {tex} A {/tex} contains one mole of nitrogen at temperature {tex} T _ { 0 } , {/tex} while Box {tex} B {/tex} contains one mole of helium at temperature {tex} ( 7 / 3 ) T _ { 0 } . {/tex} The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature. (Ignore the heat capacity of boxes. Then, the final temperature of the gases, {tex} T _ { f } {/tex}, in terms of {tex} T _ { 0 } {/tex} is

A

{tex} T _ { f } = \frac { 5 } { 2 } T _ { 0 } {/tex}

B

{tex} T _ { f } = \frac { 3 } { 7 } T _ { 0 } {/tex}

C

{tex} T _ { f } = \frac { 7 } { 3 } T _ { 0 } {/tex}

{tex} T _ { f } = \frac { 3 } { 2 } T _ { 0 } {/tex}

Explanation



Q 20.    

Correct4

Incorrect-1

When a system is taken from state {tex} i {/tex} to state {tex} f {/tex} along the path {tex} iaf, {/tex} it is found that {tex} Q = 50 {/tex} cal and {tex} W = 20 {/tex} cal. Along the path {tex} ibf \ Q = 36 {/tex} cal. W along the path {tex}ibf{/tex} is

A

{tex}14 \mathrm {\ cal} {/tex}

{tex} 6 \mathrm {\ cal } {/tex}

C

{tex} 16 \mathrm {\ cal } {/tex}

D

{tex}66 \mathrm {\ cal}{/tex}

Explanation




Q 21.    

Correct4

Incorrect-1

A Carnot engine, having an efficiency of {tex} \eta = 1 / 10 {/tex} as heat engine, is used as a refrigerator. If the work done on the system is {tex} 10 \mathrm {\ J } {/tex}, the amount of energy absorbed from the reservoir at lower temperature is

A

{tex} 100 \mathrm {\ J } {/tex}

B

{tex} 99 \mathrm {\ J } {/tex}

{tex} 90 \mathrm {\ J } {/tex}

D

{tex} 1 \mathrm {\ J } {/tex}

Explanation


Q 22.    

Correct4

Incorrect-1

If {tex} C _ { P } {/tex} and {tex} C _ { V } {/tex} denote the specific heats of nitrogen per unit mass at constant pressure and constant volume respectively, then

A

{tex} C _ { P } - C _ { V } = 28 R {/tex}

{tex} C _ { P } - C _ { V } = R / 28 {/tex}

C

{tex} C _ { P } - C _ { V } = R / 14 {/tex}

D

{tex} C _ { P } - C _ { V } = R {/tex}

Explanation



Q 23.    

Correct4

Incorrect-1

An insulated container of gas has two chambers separated by an insulating partition. One of the chambers has volume {tex} V _ { 1 } {/tex} and contains ideal gas at pressure {tex} P _ { 1 } {/tex} and temperature {tex} T _ { 1 } {/tex}. The other chamber has volume {tex} V _ { 2 } {/tex} and contains ideal gas at pressure {tex} P _ { 2 } {/tex} and temperature {tex} T _ { 2 } . {/tex} If the partition is removed without doing any work on the gas, the final equilibrium temperature of the gas in the container will be

A

{tex} \frac { T _ { 1 } T _ { 2 } \left( P _ { 1 } V _ { 1 } + P _ { 2 } V _ { 2 } \right) } { P _ { 1 } V _ { 1 } T _ { 1 } + P _ { 2 } V _ { 2 } T _ { 2 } } {/tex}

{tex} \frac { T _ { 1 } T _ { 2 } \left( P _ { 1 } V _ { 1 } + P _ { 2 } V _ { 2 } \right) } { P _ { 1 } V _ { 1 } T _ { 2 } + P _ { 2 } V _ { 2 } T _ { 1 } } {/tex}

C

{tex} \frac { P _ { 1 } V _ { 1 } T _ { 1 } + P _ { 2 } V _ { 2 } T _ { 2 } } { P _ { 1 } V _ { 1 } + P _ { 2 } V _ { 2 } } {/tex}

D

{tex} \frac { P _ { 1 } V _ { 1 } T _ { 2 } + P _ { 2 } V _ { 2 } T _ { 1 } } { P _ { 1 } V _ { 1 } + P _ { 2 } V _ { 2 } } {/tex}

Explanation



Q 24.    

Correct4

Incorrect-1

For the reactions, {tex} \mathrm { C } + \mathrm { O } _ { 2 } \rightarrow \mathrm { CO } _ { 2 } ; \quad \Delta H = -393 \mathrm { J } {/tex}
{tex} 2 \mathrm { Zn } + \mathrm { O } _ { 2 } \rightarrow 2 \mathrm { ZnO } ; \Delta H = -412 \mathrm { J } {/tex}

A

carbon can oxidise {tex} \mathrm { Zn } {/tex}

B

oxidation of carbon is not feasible

C

oxidation of {tex} \mathrm { Zn } {/tex} is not feasible

{tex} \mathrm { Zn } {/tex} can oxidise carbon.

Explanation



Q 25.    

Correct4

Incorrect-1

If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then

A

{tex} \Delta H {/tex} is {tex} - \mathrm { ve } , \Delta S {/tex} is {tex} + \mathrm { ve } {/tex}

{tex} \Delta H {/tex} and {tex} \Delta S {/tex} both are {tex} + \mathrm { ve } {/tex}

C

{tex} \Delta H {/tex} and {tex} \Delta S {/tex} both are {tex} - \mathrm { ve } {/tex}

D

{tex} \Delta H {/tex} is {tex} + \mathrm { ve } , \Delta S {/tex} is {tex} - \mathrm { ve } {/tex}

Explanation