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

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Q 1. Consider the following liquid -vapour equillibrium. Liquid {tex}\rightleftharpoons{/tex}Vapour
which of the following relations is correct?

A

{tex} \frac { d \ln P } { d T ^ { 2 } } = \frac { - \Delta H _ { v } } { T ^ { 2 } } {/tex}

{tex} \frac { d \ln P } { d T } = \frac { \Delta H _ { v } } { R T ^ { 2 } } {/tex}

C

{tex} \frac { d \ln G } { d T ^ { 2 } } = \frac { \Delta H _ { v } } { R T ^ { 2 } } {/tex}

D

{tex} \frac { d \ln P } { d T } = \frac { - \Delta H _ { v } } { R T } {/tex}

Explanation

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Q 2. The heat of combustion of carbon to {tex} \mathrm { CO } _ { 2 } {/tex} is {tex} - 393.5 \mathrm { kJ } / \mathrm { mol } . {/tex} The heat released upon formation of {tex} \mathrm { 35.2 g } {/tex} of {tex} \mathrm { CO } _ { 2 } {/tex} from carbon and oxygen gas is

{tex} - 315 \mathrm { kJ } {/tex}

B

{tex} - 630 \mathrm { kJ } {/tex}

C

{tex} - 3.15 \mathrm { kJ } {/tex}

D

None of the above

Explanation


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Q 3. For the reaction, {tex} X _ { 2 } \mathrm { O } _ { 4 ( l ) } \longrightarrow 2 \mathrm { XO } _ { 2 ( g ) } {/tex} {tex} \Delta U = 2.1 \mathrm { kcal } , \Delta S = 20 \mathrm { cal } \mathrm { K } ^ { - 1 } {/tex} at {tex} \mathrm { 300 K } {/tex}. Hence, {tex} \Delta G {/tex} is

A

{tex}2.7\ \mathrm { kcal } {/tex}

{tex} - 2.7\ \mathrm { kcal } {/tex}

C

{tex}9.3\ \mathrm { kcal } {/tex}

D

{tex} - 9.3\ \mathrm { kcal } {/tex}

Explanation




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Q 4. A reaction having equal energies of activation for forward and reverse reactions has

{tex} \Delta H = 0 {/tex}

B

{tex} \Delta H = \Delta G = \Delta S = 0 {/tex}

C

{tex} \Delta S = 0 {/tex}

D

{tex} \Delta G = 0 {/tex}

Explanation

A reaction having equal energies of activation for forward and reverse reactions has ΔH=0. The enthalpy change for a reaction is the difference in the energies of activation for forward and reverse reactions. When energies of activation for forward and reverse reactions are equal, the difference is zero.

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Q 5. When 5 litres of a gas mixture of methane and propane is perfectly combusted at 0{tex}^{\circ}{/tex}C and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in kJ ({tex}\Delta H_{comb.}{/tex}(CH{tex}_4{/tex}) = 890 kJ mol{tex}^{-1}{/tex}, {tex}\Delta H_{comb.}{/tex}(C{tex}_3{/tex}H{tex}_8{/tex})= 2220 kJ mol{tex}^{-1}{/tex} is

A

38

316

C

477

D

32

Explanation


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Q 6. Enthalpy change for the reaction, {tex}4 \mathrm { H } _ { ( g ) } \rightarrow 2 \mathrm { H } _ { 2 ( g ) } {/tex} is {tex} - 869.6 \mathrm { kJ } {/tex} The dissociation energy of {tex} \mathrm { H } - \mathrm { H } {/tex} bond is

A

{tex} - 434.8 \mathrm { kJ } {/tex}

B

{tex} - 869.6 \mathrm { kJ } {/tex}

{tex} + 434.8 \mathrm { kJ } {/tex}

D

{tex} + 217.4 \mathrm { kJ } {/tex}

Explanation

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Q 7. Which of the following is correct option for free expansion of an ideal gas under adiabatic condition?

A

{tex} q = 0 , \Delta T \neq 0 , w = 0 {/tex}

B

{tex} q \neq 0 , \Delta T = 0 , w = 0 {/tex}

{tex} q = 0 , \Delta T = 0 , w = 0 {/tex}

D

{tex} q = 0 , \Delta T < 0 , w \neq 0 {/tex}

Explanation

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Q 8. Consider the following processes:

{tex}\triangle H(kJ/mol){/tex}
1/2A {tex}\rightarrow {/tex}B +150
3B{tex}\rightarrow {/tex}2C+D -125
E+A{tex}\rightarrow {/tex}2D +350
For B+D {tex}\rightarrow{/tex} E+2C , {tex} \Delta H{/tex} will be

A

{tex}525\ \mathrm { kJ } / \mathrm { mol } {/tex}

{tex} - 175\ \mathrm { kJ } / \mathrm { mol } {/tex}

C

{tex} - 325\ \mathrm { kJ } / \mathrm { mol } {/tex}

D

{tex}325\ \mathrm { kJ } / \mathrm { mol } {/tex}

Explanation

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Q 9. Standard entropies of {tex}\mathrm X_2, \mathrm Y_2{/tex} and {tex} \mathrm {XY_3 } {/tex} are {tex}60, 40{/tex} and {tex}50{/tex} {tex}\mathrm{J K}{/tex} {tex}^{-1} {/tex} {tex}\mathrm {mol^{-1}} {/tex} respectively. For the reaction {tex}1/2\mathrm X_2 + 3/2\mathrm Y_2 \rightleftharpoons \mathrm {XY}_3, \Delta H = -\mathrm {30\ kJ} {/tex} to be at equilibrium, the temperature should be

750{tex}\ \mathrm { K } {/tex}

B

1000{tex}\ \mathrm { K } {/tex}

C

1250{tex}\ \mathrm { K } {/tex}

D

500{tex}\ \mathrm { K } {/tex}

Explanation


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Q 10. Match List I (Equations) with List II (Type of processes) and select the correct option.

List I
Equations
List II
Type of processes
A. {tex}K_p>Q{/tex} (i) Non-spontaneous
B. {tex}\triangle G^\circ<RT\ In \ Q{/tex} (ii) Equilibrium
C. {tex}K_p=Q{/tex} (iii) Spontaneous and endothermic
D. {tex}T>\frac{\triangle H}{\triangle S}{/tex} (iv) Spontaneous

A

{tex} A - ( i ) , B - ( i i ) , C - ( i i i ) , D - ( i v ) {/tex}

B

{tex} A - ( i i i ) , B - ( i v ) , C - ( i i ) , D - ( i ) {/tex}

{tex} A - ( i v ) , B - ( i ) , C - ( i i ) , D - ( i i i ) {/tex}

D

{tex} A - ( i i ) , B - ( i ) , C - ( i v ) , D - ( i i i ) {/tex}

Explanation


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Q 11. Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be

A

infinite

B

3 Joules

C

9 Joules

Zero

Explanation


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Q 12. For vaporization of water at 1 atmospheric pressure, the values of {tex} \Delta H {/tex} and {tex} \Delta S {/tex} are 40.63 {tex} \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex} and 108.8 {tex} \mathrm { J\ K } ^ { - 1 } \mathrm { mol } ^ { - 1 } {/tex} , respectively. The temperature when Gibb's energy change {tex} ( \Delta G ) {/tex} for this transformation will be zero, is

A

273.4{tex}\ \mathrm { K } {/tex}

B

393.4{tex}\ \mathrm { K } {/tex}

373.4{tex}\ \mathrm { K } {/tex}

D

293.4{tex}\ \mathrm { K } {/tex}

Explanation



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Q 13. The following two reactions are known
{tex} \mathrm { Fe } _ { 2 } \mathrm { O } _ { 3 ( s ) } + 3 \mathrm { CO } _ { ( g ) } \rightarrow 2 \mathrm { Fe } _ { ( s ) } + 3 \mathrm { CO } _ { 2 ( g )}; \Delta H = - 26.8 \mathrm { kJ } {/tex}
{tex} \mathrm { FeO } _ { ( s ) } + \mathrm { CO } _ { ( g ) } \rightarrow \mathrm { Fe } _ { ( s ) } + \mathrm { CO } _ { 2 ( g ) } ; \Delta H = - 16.5 \mathrm { kJ } {/tex}
The value of {tex} \Delta H {/tex} for the following reaction
{tex} \mathrm { Fe } _ { 2 } \mathrm { O } _ { 3 ( s ) } + \mathrm { CO } _ { ( g ) } \rightarrow 2 \mathrm { FeO } _ { ( s ) } + \mathrm { CO } _ { 2 ( g ) } {/tex} is

A

{tex} + 10.3\ \mathrm { kJ } {/tex}

B

{tex} - 43.3\ \mathrm { kJ } {/tex}

C

{tex} - 10.3\ \mathrm { kJ } {/tex}

{tex} + 6.2\ \mathrm { kJ } {/tex}

Explanation


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Q 14. The values of {tex} \Delta H{/tex} and {tex} \Delta S{/tex} for the reaction,
{tex} C_{(graphite)} + CO_{2(g)} \rightarrow 2CO_{(g)}{/tex}
are 170 kJ and 170 J K{tex}^{-1}{/tex}, respectively. This reaction will be spontaneous at

A

910{tex}\ \mathrm { K } {/tex}

1110{tex}\ \mathrm { K } {/tex}

C

510{tex}\ \mathrm { K } {/tex}

D

710{tex}\ \mathrm { K } {/tex}

Explanation


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Q 15. From the following bond energies :
{tex} \mathrm{ H \bm {-} H \ bond\ energy \ \ \ \ :\ 431.37\ kJ\ mol^{-1} } {/tex}
{tex} \mathrm{ C \bm {=} C\ bond\ energy \ \ \ \ :\ 606.10\ kJ\ mol^{-1} } {/tex}
{tex} \mathrm{ C \bm {-} C\ bond\ energy \ \ \ \ :\ 336.49\ kJ\ mol^{-1} } {/tex}
{tex} \mathrm{ C \bm {-} H\ bond\ energy \ \ \ \ :\ 410.50\ kJ\ mol^{-1} } {/tex}
Enthalpy for the reaction,
will be

A

{tex} - 243.6\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

{tex} - 120.0\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

C

{tex}553.0\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

D

{tex}1523.6\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

Explanation


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Q 16. Bond dissociation enthalpy of {tex} \mathrm { H } _ { 2 } , \mathrm { Cl } _ { 2 } {/tex} and {tex} \mathrm { HCl } {/tex} are {tex} 434,242 {/tex} and {tex}431\ \mathrm { mol } ^ { - 1 } {/tex}respectively. Enthalpy of formation of {tex} \mathrm { HCl } {/tex} is

{tex} - 93\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

B

{tex}245\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

C

{tex}93\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

D

{tex} - 245\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

Explanation


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Q 17. For the gas phase reaction,
{tex} \mathrm {PCl_{5(g)}}\ \rightleftharpoons \ \mathrm {PCl_{3(g)}} + \mathrm {Cl_{2(g)}} {/tex}
which of the following conditions are correct?

A

{tex} \Delta H < 0 {/tex} and {tex} \Delta S < 0 {/tex}

B

{tex} \Delta H > 0 {/tex} and {tex} \Delta S < 0 {/tex}

C

{tex} \Delta H = 0 {/tex} and {tex} \Delta S < 0 {/tex}

{tex} \Delta H > 0 {/tex} and {tex} \Delta S > 0 {/tex}

Explanation


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Q 18. Which of the following are not state functions?
{tex} \mathrm{(I)}\ q+w{/tex}
{tex} \mathrm{(II)}\ q{/tex}
{tex} \mathrm{(III)}\ w{/tex}
{tex} \mathrm{(IV)}\ H-TS {/tex}

A

{tex} \mathrm { (I),\ (II)\ and\ (III) }{/tex}

{tex} \mathrm { (II)\ and\ (III) }{/tex}

C

{tex} \mathrm { (I)\ and\ (IV) }{/tex}

D

{tex} \mathrm { (II),\ (III)\ and\ (IV) }{/tex}

Explanation


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Q 19. Consider the following reactions:
{tex}\mathrm {(i)}\ \mathrm{ H^+}_{(aq)} + \mathrm{ OH^-}_{(aq)} = \mathrm{ H_2O_{(l)}}, \ \Delta H = -X_1\ \mathrm {{kJ}\ mol^{-1}} {/tex}
{tex}\mathrm {(ii)}\ \mathrm{ H}_{2(g)} + \mathrm{ 1/2 O}_{2(g)} = \mathrm{ H_2O_{(l)}}, \ \Delta H = -X_2\ \mathrm {{kJ}\ mol^{-1}} {/tex}
{tex}\mathrm {(iii)}\ \mathrm{ CO}_{2(g)} + \mathrm{ H}_{2(g)} = \mathrm{ CO_{(g)} + \mathrm{ H_2O_{(l)}}}, \ \Delta H = -X_3\ \mathrm {{kJ}\ mol^{-1}} {/tex}
{tex}\mathrm {(iv)}\ \mathrm{C_2 H}_{2(g)} + \mathrm{ 5/2O}_{2(g)} = \mathrm{2CO_{2(g)} + \mathrm{ H_2O_{(l)}}}, \ \Delta H = +X_4\ \mathrm {{kJ}\ mol^{-1}} {/tex}
Enthalpy of formation of {tex}\mathrm {H_2O}_{(l)}{/tex} is

A

{tex} + \mathrm X _ { 3 }\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

B

{tex} - \mathrm X _ { 4 }\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

C

{tex} + \mathrm X _ { 1 }\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

{tex} - \mathrm X _ { 2 }\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

Explanation


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Q 20. Given that bond energies of {tex} \mathrm { H } - \mathrm { H } {/tex} and {tex} \mathrm { Cl } - \mathrm { Cl } {/tex} are 430{tex}\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex} and 240{tex}\ \mathrm { kJ } \ \mathrm { mol } ^ { - 1 } {/tex},respectively and {tex} \Delta H _ { f } {/tex} for {tex} \mathrm { HCl } {/tex} is - 90{tex} \ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex} , bond enthalpy of {tex} \mathrm { HCl } {/tex} is

A

380{tex}\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

425{tex}\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

C

245{tex}\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

D

290{tex}\ \mathrm { kJ }\ \mathrm { mol } ^ { - 1 } {/tex}

Explanation


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Q 21. Identify the correct statement for change of Gibb's energy for a system ( {tex} \Delta G _ { \text {system } }) {/tex} at constant temperature and pressure.

A

If {tex} \Delta G _ { \text {system } } < 0 , {/tex} the process is not spontaneous.

B

If {tex} \Delta G _ { \text {system } } > 0 , {/tex} the process is spontaneous.

If {tex} \Delta G _ { \text {system } } = 0 , {/tex} the system has attained equilibrium.

D

If {tex} \Delta G _ { \text {system } } = 0 , {/tex} the system is still moving in a particular direction.

Explanation