Question 1: Palette 1/130

JEE Mains 2026 MCQ

The plot of $\log_{10} K$ vs $\frac{1}{T}$ gives a straight line. The intercept and slope respectively are (where K is equilibrium constant).

A

$-\frac{\Delta S^{\circ} R}{2.303}, \frac{\Delta H^{\circ} R}{2.303}$

B

$-\frac{\Delta H^{\circ}}{2.303R}, \frac{\Delta S^{\circ}}{2.303R}$

C

$\frac{\Delta S^{\circ}}{2.303R}, -\frac{\Delta H^{\circ}}{2.303R}$

D

$\frac{2.303R}{\Delta H^{\circ}}, \frac{2.303R}{\Delta S^{\circ}}$

Question 2: Palette 2/130

JEE Mains 2026 MCQ

$20.0 \mathrm{dm}^3$ of an ideal gas ' X ' at 600 K and 0.5 MPa undergoes isothermal reversible expansion until pressure of the gas is 0.2 MPa . Which of the following option is correct?

(Given: $\log 2=0.3010$ and $\log 5=0.6989$ )

A

$\mathrm{w}=-9.1 \mathrm{~kJ}, \Delta \mathrm{U}=0, \Delta \mathrm{H}=0, \mathrm{q}=9.1 \mathrm{~kJ}$

B

$\mathrm{w}=9.1 \mathrm{~J}, \Delta \mathrm{U}=9.1 \mathrm{~J}, \Delta \mathrm{H}=0 ; \mathrm{q}=0$

C

$\mathrm{w}=-3.9 \mathrm{~kJ}, \Delta \mathrm{U}=0, \Delta \mathrm{H}=0 ; \mathrm{q}=3.9 \mathrm{~kJ}$

D

$\mathrm{w}=+4.1 \mathrm{~kJ}, \Delta \mathrm{U}=0, \Delta \mathrm{H}=0 ; \mathrm{q}=-4.1 \mathrm{~kJ}$

Question 3: Palette 3/130

JEE Mains 2026 MCQ

The heat of atomisation of methane and ethane are ' x ' $\mathrm{kJ} \mathrm{mol}^{-1}$ and ' y ' $\mathrm{kJ} \mathrm{mol}^{-1}$ respectively. The longest wavelength ( $\lambda$ ) of light capable of breaking the $\mathrm{C}-\mathrm{C}$ bond can be expressed in SI unit as :

A

$\frac{\mathrm{N}_{\mathrm{A}} \mathrm{hc}}{250(y-6 x)}$

B

$\mathrm{N}_{\mathrm{A}} \mathrm{hc}\left(y-\frac{6 x}{4}\right)^{-1}$

C

$\frac{\mathrm{hc}}{1000}\left(\frac{y-6 x}{4}\right)^{-1}$

D

$\frac{\mathrm{N}_{\mathrm{A}} \mathrm{hc}}{250(4 y-6 x)}$

Question 4: Palette 4/130

JEE Mains 2026 MCQ

$ \text { Match the LIST-I with LIST-II } $

List-I Isothermal process for ideal gas system		List-II Work done ( ${}_{}$ <mi>V</mi> <mi>f</mi> > <mi>V</mi> <mi>i</mi> ${}_{}$ <mi>V</mi> <mi>f</mi> > <mi>V</mi> <mi>i</mi> V_(f) > V_(i) )
A.	Reversible expansion	I.	$$ <mi mathvariant="normal">w</mi> = 0 $$ <mi mathvariant="normal">w</mi> = 0 w=0
B.	Free expansion	II.	$$ <mi mathvariant="normal">w</mi> = − <mi data-mjx-auto-op="false">nR</mi> T ln ⁡ <msub> <mrow data-mjx-texclass="ORD"> <mtext> </mtext> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">f</mi> </mrow> </mrow> </msub> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> $$ <mi mathvariant="normal">w</mi> = − <mi data-mjx-auto-op="false">nR</mi> T ln ⁡ <msub> <mrow data-mjx-texclass="ORD"> <mtext></mtext> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">f</mi> </mrow> </mrow> </msub> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> w=-nRT ln((V_(f))/(V_(i)))
C.	Irreversible expansion	III.	$$ <mi mathvariant="normal">w</mi> = − <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">p</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">ex</mi> </mrow> </mrow> <mo data-mjx-texclass="OPEN">(</mo> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">f</mi> </mrow> </mrow> </msub> <mo>−</mo> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> <mo data-mjx-texclass="CLOSE">)</mo> $$ <mi mathvariant="normal">w</mi> = − <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">p</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">ex</mi> </mrow> </mrow> <mrow> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">f</mi> </mrow> </mrow> </msub> <mo>−</mo> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> </mrow> w=-p_(ex)(V_(f)-V_(i))
D.	Irreversible compression	IV.	$$ <mi mathvariant="normal">w</mi> = − <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">p</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">ex</mi> </mrow> </mrow> <mo data-mjx-texclass="OPEN">(</mo> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> <mo>−</mo> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">f</mi> </mrow> </mrow> </msub> <mo data-mjx-texclass="CLOSE">)</mo> $$ <mi mathvariant="normal">w</mi> = − <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">p</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">ex</mi> </mrow> </mrow> <mrow> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> <mo>−</mo> <msub> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">f</mi> </mrow> </mrow> </msub> </mrow> w=-p_(ex)(V_(i)-V_(f))

Choose the correct answer from the options given below:

A

A-IV, B-I, C-III, D-II

B

A-I, B-III, C-II, D-IV

C

A-II, B-I, C-III, D-IV

D

A-IV, B-II, C-III, D-I

Question 5: Palette 5/130

JEE Mains 2026 MCQ

A cup of water at $5^{\circ} \mathrm{C}$ (system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true?

A

$q=+v e, w=-v e, \Delta U=+v e$

B

$q=+v e, w=0, \Delta U=-v e$

C

$q=+v e, w=-v e, \Delta U=-v e$

D

$q=-v e, w=-v e, \Delta U=-v e$

Question 6: Palette 6/130

JEE Mains 2026 MCQ

$ \text { Match the LIST-I with LIST-II } $

List-I Thermodynamic Process		List-II Magnitude in kJ
A.	Work done in reversible, isothermal expansion of 2 mol of ideal gas from $2{}^{}$ <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">dm</mi> </mrow> <mn>3</mn> $2{}^{}$ <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">dm</mi> </mrow> <mn>3</mn> 2dm^(3) to $20{}^{}$ <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">dm</mi> </mrow> <mn>3</mn> $20{}^{}$ <mrow data-mjx-texclass="ORD"> <mi data-mjx-auto-op="false">dm</mi> </mrow> <mn>3</mn> 20dm^(3) at 300 K .	I.	4
B.	Work done in irreversible isothermal expansion of 1 mol ideal gas from $1{}^{}$ <mrow data-mjx-texclass="ORD"> <mtext> </mtext> <mi mathvariant="normal">m</mi> </mrow> <mn>3</mn> $1{}^{}$ <mrow data-mjx-texclass="ORD"> <mtext></mtext> <mi mathvariant="normal">m</mi> </mrow> <mn>3</mn> 1m^(3) to $3{}^{}$ <mrow data-mjx-texclass="ORD"> <mtext> </mtext> <mi mathvariant="normal">m</mi> </mrow> <mn>3</mn> $3{}^{}$ <mrow data-mjx-texclass="ORD"> <mtext></mtext> <mi mathvariant="normal">m</mi> </mrow> <mn>3</mn> 3m^(3) at 300 K against a constant pressure of 3 kPa .	II.	11.5
C.	Change in internal energy for adiabatic expansion of a 1 mol ideal gas with change of temperature $=320$ <mtext> </mtext> <mi mathvariant="normal">K</mi> $=320$ <mtext></mtext> <mi mathvariant="normal">K</mi> =320K and ${}_{}$ <mover> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">C</mi> </mrow> <mo accent="true">―</mo> </mover> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> </mrow> = <mn>3</mn> <mn>2</mn> <mi mathvariant="normal">R</mi> ${}_{}$ <mover accentunder="false"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">C</mi> </mrow> <mo>¯</mo> </mover> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">V</mi> </mrow> </mrow> = <mn>3</mn> <mn>2</mn> <mi mathvariant="normal">R</mi> bar(C)_(V)=(3)/(2)R.	III.	6
D.	Change in enthalpy at constant pressure of 1 mol ideal gas with change of temperature $=337$ <mtext> </mtext> <mi mathvariant="normal">K</mi> $=337$ <mtext></mtext> <mi mathvariant="normal">K</mi> =337K and ${}_{}$ <mover> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">C</mi> </mrow> <mo accent="true">―</mo> </mover> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">p</mi> </mrow> </mrow> = <mn>5</mn> <mn>2</mn> <mi mathvariant="normal">R</mi> ${}_{}$ <mover accentunder="false"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">C</mi> </mrow> <mo>¯</mo> </mover> <mrow data-mjx-texclass="ORD"> <mrow data-mjx-texclass="ORD"> <mi mathvariant="normal">p</mi> </mrow> </mrow> = <mn>5</mn> <mn>2</mn> <mi mathvariant="normal">R</mi> bar(C)_(p)=(5)/(2)R.	IV.	7

A

A-I, B-II, C-III, D-IV

B

A-III, B-II, C-IV, D-I

C

A-II, B-I, C-III, D-IV

D

A-II, B-III, C-I, D-IV

Question 7: Palette 7/130

JEE Mains 2026 MCQ

Consider the following data :

$\Delta_{f}H^{\circ}$ (methane, g) = $-X \; \text{kJ mol}^{-1}$

Enthalpy of sublimation of graphite = $Y \; \text{kJ mol}^{-1}$

Dissociation enthalpy of $H_2 = Z \; \text{kJ mol}^{-1}$

The bond enthalpy of C–H bond is given by :

A

$ \dfrac{X + Y + 2Z}{4} $

B

$ \dfrac{X + Y + 4Z}{2} $

C

$ \dfrac{-X + Y + Z}{4} $

D

$X + Y + Z$

Question 8: Palette 8/130

JEE Mains 2026 MCQ

Which of the following graphs between pressure ' p ' versus volume ' V ' represents the maximum work done?

A

B

C

D

Question 9: Palette 9/130

JEE Mains 2026 MCQ

For the reaction, $\mathrm{N}_2 \mathrm{O}_4 \rightleftharpoons 2 \mathrm{NO}_2$, graph is plotted as shown below. Identify correct statements.

A. Standard free energy change for the reaction is $-5.40 \mathrm{~kJ} \mathrm{~mol}^{-1}$.

B. As $\Delta \mathrm{G}^{\ominus}$ in graph is positive, $\mathrm{N}_2 \mathrm{O}_4$ will not dissociate into $\mathrm{NO}_2$ at all.

C. Reverse reaction will go to completion.

D. When 1 mole of $\mathrm{N}_2 \mathrm{O}_4$ changes into equilibrium mixture, value of $\Delta \mathrm{G}^{\ominus}=-0.84 \mathrm{~kJ} \mathrm{~mol}^{-1}$

E. When 2 mole of $\mathrm{NO}_2$ changes into equilibrium mixture, $\Delta \mathrm{G}^{\ominus}$ for equilibrium mixture is $-6.24 \mathrm{~kJ} \mathrm{~mol}^{-1}$.

Choose the correct answer from the options given below :

A

C and E only

B

D and E only

C

A and D only

D

B and C only

Question 10: Palette 10/130

JEE Mains 2026 MCQ

Match List - I with List - II.

Given $V_1$ and $V_2$ are initial and final volumes respectively.

List - I (Isothermal process)		List - II (Expression)
A.	Reversible expansion	I.	$ \mathrm{q}=0 $
B.	Free expansion	II.	$ \mathrm{q}=\mathrm{nRT} \ln \frac{\mathrm{~V}_2}{\mathrm{~V}_1} $
C.	Irreversible Compression	III.	$ \mathrm{w}=-\mathrm{p}_{\mathrm{ext}}\left(\mathrm{~V}_1-\mathrm{V}_2\right) $
D.	Cyclic reversible	IV.	$ \frac{\mathrm{q}_{\mathrm{rev}}}{\mathrm{~T}}=0 $

Choose the correct answer from the options given below :

A

A-II, B-III, C-I, D-IV

B

A-II, B-I, C-IV, D-III

C

A-II, B-I, C-III, D-IV

D

A-I, B-II, C-III, D-IV

Question 11: Palette 11/130

JEE Mains 2026 MCQ

Arrange the following isothermal processes in order of the magnitude of the work $(\mathrm{p}-\mathrm{V})$ involved between states 1 and 2.

A. Expansion in single stage $\mathrm{w}_{\mathrm{A}}$

B. Expansion in multi stages $w_B$

C. Compression in single stage $\mathrm{w}_{\mathrm{C}}$

D. Compression in multi stages $w_D$

Choose the correct option.

A

$ \left|w_B\right|>\left|w_A\right|>\left|w_C\right|>\left|w_D\right| $

B

$ \left|w_C\right|>\left|w_D\right|>\left|w_A\right|>\left|w_B\right| $

C

$ \left|w_C\right|>\left|w_D\right|>\left|w_B\right|>\left|w_A\right| $

D

$ \left|w_B\right|>\left|w_A\right|>\left|w_D\right|>\left|w_C\right| $

Question 12: Palette 12/130

JEE Mains 2026 MCQ

Consider the following data for the reaction

$ X_2(g)+Y_2(g) \rightleftharpoons 2 X Y(g) $

at $600 \mathrm{~K}^{\circ}$. The $\Delta_{\mathrm{r}} \mathrm{G}^{\ominus}$ (in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) for the reaction is :

$ \begin{array}{|c|c|c|} \hline \text { Compound } & \Delta_f \mathrm{H}_{600 \mathrm{~K}}^{\ominus}\left(\mathrm{kJ} \mathrm{~mol}^{-1}\right) & \mathrm{S}^{\ominus}{ }_{600 \mathrm{~K}}\left(\mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\right) \\ \hline \mathrm{XY}(\mathrm{~g}) & 42 & 200 \\ \hline \mathrm{X}_2(\mathrm{~g}) & 8 & 140 \\ \hline \mathrm{Y}_2(\mathrm{~g}) & 80 & 250 \\ \hline \end{array} $

A

-21000

B

-10

C

-1000

D

-9.012

Question 13: Palette 13/130

JEE Mains 2026 MCQ

The correct order of molar heat capacities measured at 298 K and 1 bar is :

A

Copper(s) $>$ Bromine(l) $>$ Helium(g)

B

Bromine(l) > Copper(s) > Helium(g)

C

Helium(g) > Bromine(l) > Copper(s)

D

Helium(g) > Bromine(l) = Copper(s)

Question 14: Palette 14/130

JEE Mains 2026 MCQ

Given below are two statements :

Statement I : For an ideal gas, heat capacity at constant volume is always greater than the heat capacity at constant pressure.

Statement II : In a constant volume process, no work is produced and all the heat withdrawn goes into the chaotic motion and is reflected by a temperature increase of the ideal gas.

In the light of the above statements, choose the correct answer from the options given below

A

Both Statement I and Statement II are true

B

Both Statement I and Statement II are false

C

Statement I is true but Statement II is false

D

Statement I is false but Statement II is true

Question 15: Palette 15/130

JEE Mains 2026 MCQ

Gas 'A' undergoes change from state 'X' to state 'Y'. In this process, the heat absorbed and work done by the gas is 10 J and 18 J respectively. Now gas is brought back to state 'X' by another process during which 6 J of heat is evolved. In the reverse process of 'Y' to 'X',

A

18 J of the work is done by the gas 'A'.

B

2 J of the work is done by the gas 'A'.

C

12 J of the work is done on the gas 'A' by the surrounding.

D

14 J of the work is done on the gas 'A' by the surrounding.

Question 16: Palette 16/130

JEE Mains 2026 MCQ

Consider the following data.

(i) $2\text{Al(s)} + 6\text{HCl(aq)} \rightarrow \text{Al}_2\text{Cl}_6\text{(aq)} + 3\text{H}_2\text{(g)} + 1200~\text{kJ/mol}$

(ii) $\text{H}_2\text{(g)} + \text{Cl}_2\text{(g)} \rightarrow 2\text{HCl(g)} + 164~\text{kJ/mol}$

(iii) $\text{HCl(g)} + \text{aq} \rightarrow \text{HCl(aq)} + 83~\text{kJ/mol}$

(iv) $\text{Al}_2\text{Cl}_6\text{(s)} + \text{aq} \rightarrow \text{Al}_2\text{Cl}_6\text{(aq)} + 663~\text{kJ/mol}$

The enthalpy of formation of anhydrous solid $\text{Al}_2\text{Cl}_6$ is :

A

$-648~\text{kJ}~\text{mol}^{-1}$

B

$-1350~\text{kJ}~\text{mol}^{-1}$

C

$-2002~\text{kJ}~\text{mol}^{-1}$

D

$-1527~\text{kJ}~\text{mol}^{-1}$

Question 17: Palette 17/130

JEE Mains 2025 MCQ

The hydration energies of $K^+$ and $Cl^-$ are $-x$ and $-y$ kJ/mol respectively. If the lattice energy of KCl is $-z$ kJ/mol, then the heat of solution of KCl is :

A

$x + y + z$

B

$z - (x + y)$

C

$-z - (x + y)$

D

$x - y - z$

Question 18: Palette 18/130

JEE Mains 2025 MCQ

The correct statement amongst the following is :

A

The standard state of a pure gas is the pure gas at a pressure of 1 bar and temperature 273 K.

B

$\Delta_f H^{\circ}_{500}$ is zero for $O_2(g)$.

C

$\Delta_f H^{\circ}_{298}$ is zero for $O(g)$.

D

The term 'standard state' implies that the temperature is 0°C.

Question 19: Palette 19/130

JEE Mains 2025 MCQ

Total enthalpy change for freezing of 1 mol of water at $10^{\circ} \mathrm{C}$ to ice at $-10^{\circ} \mathrm{C}$ is ________

(Given: $\Delta_{\text {fus }} \mathrm{H}=x \mathrm{~kJ} / \mathrm{mol}$

$\begin{aligned} & \mathrm{C}_{\mathrm{p}}\left[\mathrm{H}_2 \mathrm{O}(\mathrm{l})\right]=y \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1} \\ & \mathrm{C}_{\mathrm{p}}\left[\mathrm{H}_2 \mathrm{O}(\mathrm{~s})\right]=z \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1} \end{aligned}$

A

$-x-10 y-10 z$

B

$x-10 y-10 z$

C

$-10(100 x+y+z)$

D

$10(100 \mathrm{x}+y+z)$

Question 20: Palette 20/130

JEE Mains 2025 MCQ

Consider the given data :

(a) $\mathrm{HCl}(\mathrm{g})+10 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{HCl} .10 \mathrm{H}_2 \mathrm{O} \Delta \mathrm{H}=-69.01 \mathrm{~kJ} \mathrm{~mol}^{-1}$

(b) $\mathrm{HCl}(\mathrm{g})+40 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{HCl} .40 \mathrm{H}_2 \mathrm{O} \Delta \mathrm{H}=-72.79 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Choose the correct statement :

A

The heat of dilution for the $\mathrm{HCl}\left(\mathrm{HCl} .10 \mathrm{H}_2 \mathrm{O}\right.$ to $\left.\mathrm{HCl} .40 \mathrm{H}_2 \mathrm{O}\right)$ is $3.78 \mathrm{~kJ} \mathrm{~mol}^{-1}$.

B

Dissolution of gas in water is an endothermic process.

C

The heat of solution depends on the amount of solvent.

D

The heat of formation of HCl solution is represented by both (a) and (b).

Question 21: Palette 21/130

JEE Mains 2025 MCQ

One mole of an ideal gas expands isothermally and reversibly from $10 \mathrm{dm}^3$ to $20 \mathrm{dm}^3$ at 300 K . $\Delta \mathrm{U}, \mathrm{q}$ and work done in the process respectively are

Given: $\mathrm{R}=8.3 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$

$\ln 10=2.3$

$\log 2=0.30$

$\log 3=0.48$

A

$0,21.84 \mathrm{~kJ},-1.726 \mathrm{~J}$

B

$0,21.84 \mathrm{~kJ}, 21.84 \mathrm{~kJ}$

C

$0,1.718 \mathrm{~kJ},-1.718 \mathrm{~kJ}$

D

$0,-17.18 \mathrm{~kJ}, 1.718 \mathrm{~J}$

Question 22: Palette 22/130

JEE Mains 2025 MCQ

Let us consider a reversible reaction at temperature, T. In this reaction, both $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ were observed to have positive values. If the equilibrium temperature is Te , then the reaction becomes spontaneous at:

A

$\mathrm{Te}>\mathrm{T}$

B

$\mathrm{T}>\mathrm{Te}$

C

$\mathrm{T}=\mathrm{Te}$

D

$\mathrm{Te}=5 \mathrm{~T}$

Question 23: Palette 23/130

JEE Mains 2025 MCQ

Given below are two statements:

Statement I : When a system containing ice in equilibrium with water (liquid) is heated, heat is absorbed by the system and there is no change in the temperature of the system until whole ice gets melted.

Statement II : At melting point of ice, there is absorption of heat in order to overcome intermolecular forces of attraction within the molecules of water in ice and kinetic energy of molecules is not increased at melting point.

In the light of the above statements, choose the correct answer from the options given below

A

Both Statement I and Statement II are false

B

Statement I is true but Statement II is false

C

Both Statement I and Statement II are true

D

Statement I is false but Statement II is true

Question 24: Palette 24/130

JEE Mains 2025 MCQ

Arrange the following in order of magnitude of work done by the system/on the system at constant temperature.

(a) $\left|w_{\text {reversible }}\right|$ for expansion in infinite stages.

(b) $\left|w_{\text {irreversible }}\right|$ for expansion in single stage.

(c) $\left|\mathrm{w}_{\text {reversible }}\right|$ for compression in infinite stages.

(d) $\left|w_{\text {irreversible }}\right|$ for compression in single stage.

Choose the correct answer from the options given below :

A

$\mathbf{}_{} \mathrm{d}>\mathrm{c}=\mathrm{a}>\mathrm{b}$

B

$\mathrm{c}=\mathrm{a}>\mathrm{d}>\mathrm{b}$

C

$a>c>b>d$

D

$a>b>c>d$

Question 25: Palette 25/130

JEE Mains 2025 MCQ

Which of the following graphs correctly represents the variation of thermodynamic properties of Haber's process?

A

B

C

D

Question 26: Palette 26/130

JEE Mains 2025 MCQ

Two vessels A and B are connected via stopcock. The vessel A is filled with a gas at a certain pressure. The entire assembly is immersed in water and is allowed to come to thermal equilibrium with water. After opening the stopcock the gas from vessel A expands into vessel B and no change in temperature is observed in the thermometer. Which of the following statement is true ?

A

$\mathrm{dq} \neq 0$

B

The pressure in the vessel B before opening the stopcock is zero

C

$\mathrm{dw} \neq 0$

D

$\mathrm{dU} \neq 0$

Question 27: Palette 27/130

JEE Mains 2025 MCQ

If $\quad C$ (diamond $) \rightarrow C$ (graphite) $+X \mathrm{~kJ} \mathrm{~mol}^{-1}$

C (diamond) $+\mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2(\mathrm{~g})+\mathrm{Y} \mathrm{kJ} \mathrm{mol}{ }^{-1}$

C (graphite) $+\mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{CO}_2(\mathrm{~g})+\mathrm{Z} \mathrm{kJ} \mathrm{mol}^{-1}$

at constant temperature. Then

A

−X = Y + Z

B

X = Y − Z

C

X = −Y + Z

D

X = Y + Z

Question 28: Palette 28/130

JEE Mains 2025 MCQ

500 J of energy is transferred as heat to 0.5 mol of Argon gas at 298 K and 1.00 atm. The final temperature and the change in internal energy respectively are: Given: R = 8.3 J K^-1 mol^-1

A

368 K and 500 J

B

348 K and 300 J

C

378 K and 300 J

D

378 K and 500 J

Question 29: Palette 29/130

JEE Mains 2025 MCQ

An ideal gas undergoes a cyclic transformation starting from the point A and coming back to the same point by tracing the path A→B→C→D→A as shown in the three cases above.

Choose the correct option regarding ΔU :

A

$\Delta \mathrm{U}(\text { Case-III })>\Delta \mathrm{U}(\text { Case-II })>\Delta \mathrm{U}(\text { Case-I })$

B

$\Delta \mathrm{U}($ Case-I $)>\Delta \mathrm{U}($ Case-II $)>\Delta \mathrm{U}($ Case-III $)$

C

$\Delta \mathrm{U}($ Case-I $)=\Delta \mathrm{U}($ Case-II $)=\Delta \mathrm{U}($ Case-III $)$

D

$\Delta \mathrm{U}($ Case-I $)>\Delta \mathrm{U}($ Case-III $)>\Delta \mathrm{U}($ Case-II $)$

Question 30: Palette 30/130

JEE Mains 2025 MCQ

Ice and water are placed in a closed container at a pressure of 1 atm and temperature 273.15 K . If pressure of the system is increased 2 times, keeping temperature constant, then identify correct observation from following

A

Liquid phase disappears completely.

B

The amount of ice decreases.

C

The solid phase (ice) disappears completely.

D

Volume of system increases .

Question 31: Palette 31/130

JEE Mains 2025 MCQ

$\begin{aligned} & \mathrm{S}(\mathrm{~g})+\frac{3}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{SO}_3(\mathrm{~g})+2 x \mathrm{kcal} \\ & \mathrm{SO}_2(\mathrm{~g})+\frac{1}{2} \mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{SO}_3(\mathrm{~g})+y \mathrm{kcal} \end{aligned}$

The heat of formation of $\mathrm{SO}_2(\mathrm{~g})$ is given by :

A

$2 x+y$ kcal

B

$\frac{2 x}{y} \mathrm{~kcal}$

C

$y-2 x \mathrm{~kcal}$

D

$x+y \mathrm{~kcal}$

Question 32: Palette 32/130

JEE Mains 2025 MCQ

Which of the following mixing of 1 M base and 1 M acid leads to the largest increase in temperature?

A

50 mL HCl and 20 mL NaOH

B

30 mL HCl and 30 mL NaOH

C

$45 \mathrm{~mL} \mathrm{~CH}_3 \mathrm{COOH}$ and 25 mL NaOH

D

$30 \mathrm{~mL} \mathrm{~CH}_3 \mathrm{COOH}$ and 30 mL NaOH

Question 33: Palette 33/130

JEE Mains 2025 MCQ

Let us consider an endothermic reaction which is non-spontaneous at the freezing point of water. However, the reaction is spontaneous at boiling point of water. Choose the correct option.

A

Both $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ are (-ve)

B

$\Delta \mathrm{H}$ is $(+\mathrm{ve})$ but $\Delta \mathrm{S}$ is (-ve)

C

$\Delta \mathrm{H}$ is $(-\mathrm{ve})$ but $\Delta \mathrm{S}$ is (+ve)

D

Both $\Delta \mathrm{H}$ and $\Delta \mathrm{S}$ are (+ve)

Question 34: Palette 34/130

JEE Mains 2025 MCQ

The effect of temperature on spontaneity of reactions are represented as :

	$\Delta$H	$\Delta$S	Temperature	Spontaneity
(A)	$+$	$-$	any T	Non spontaneous
(B)	$+$	$+$	low T	spontaneous
(C)	$-$	$-$	low T	Non spontaneous
(D)	$-$	$+$	any T	spontaneous

The incorrect combinations are :

A

(A) and (C) only

B

(B) and (D) only

C

(A) and (D) only

D

(B) and (C) only

Question 35: Palette 35/130

JEE Mains 2025 MCQ

Ice at $-5^{\circ} \mathrm{C}$ is heated to become vapor with temperature of $110^{\circ} \mathrm{C}$ at atmospheric pressure. The entropy change associated with this process can be obtained from

A

$\int_{268 \mathrm{~K}}^{273 \mathrm{~K}} \mathrm{C}_{\mathrm{p}, \mathrm{m}} \mathrm{dT}+\frac{\Delta \mathrm{H}_{\mathrm{m}} \text {, fusion }}{\mathrm{T}_{\mathrm{f}}}+\frac{\Delta \mathrm{H}_{\mathrm{m}, \text { vaporisation }}}{\mathrm{T}_{\mathrm{b}}}+\int_{273 \mathrm{~K}}^{373 \mathrm{~K}} \mathrm{C}_{\mathrm{p}, \mathrm{m}} \mathrm{dT}+\int_{373 \mathrm{~K}}^{383 \mathrm{~K}} \mathrm{C}_{\mathrm{p}, \mathrm{m}} \mathrm{dT}$

B

$\int_{268 \mathrm{~K}}^{383 \mathrm{~K}} \mathrm{C}_{\mathrm{p}} \mathrm{dT}+\frac{\Delta \mathrm{H}_{\text {melting }}}{273}+\frac{\Delta \mathrm{H}_{\text {boiling }}}{373}$

C

$\int_{268 \mathrm{~K}}^{383 \mathrm{~K}} \mathrm{C}_{\mathrm{p}} \mathrm{dT}+\frac{\mathrm{q}_{\text {rev }}}{\mathrm{T}}$

D

$\int_{268 \mathrm{~K}}^{273 \mathrm{~K}} \frac{\mathrm{C}_{\mathrm{p}, \mathrm{m}}}{\mathrm{T}} \mathrm{dT}+\frac{\Delta \mathrm{H}_{\mathrm{m}}, \text { fusion }}{\mathrm{T}_{\mathrm{f}}}+\frac{\Delta \mathrm{H}_{\mathrm{m}, \text { vaporisation }}^{373 \mathrm{~K}}}{\mathrm{~T}_{\mathrm{b}}}+\int_{273 \mathrm{~K}} \frac{\mathrm{C}_{\mathrm{p}, \mathrm{m}} \mathrm{dT}}{T}+\int_{373 \mathrm{~K}}^{383 \mathrm{~K}} \frac{\mathrm{C}_{\mathrm{p}, \mathrm{m}} \mathrm{dT}}{\mathrm{T}}$

Question 36: Palette 36/130

JEE Mains 2025 MCQ

Match List - I with List - II.

	List - I (Partial Derivatives)		List - II (Thermodynamic Quantity)
(A)	$\left(\frac{\partial \mathrm{G}}{\partial \mathrm{T}}\right)_{\mathrm{P}}$	(I)	Cp
(B)	$\left(\frac{\partial \mathrm{H}}{\partial \mathrm{T}}\right)_{\mathrm{P}}$	(II)	$-$S
(C)	$\left(\frac{\partial \mathrm{G}}{\partial \mathrm{P}}\right)_{\mathrm{T}}$	(III)	Cv
(D)	$\left(\frac{\partial \mathrm{U}}{\partial \mathrm{T}}\right)_{\mathrm{V}}$	(IV)	V

Choose the correct answer from the options given below :

A

(A)-(I), (B)-(II), (C)-(IV), (D)-(III)

B

(A)-(II), (B)-(III), (C)-(I), (D)-(IV)

C

(A)-(II), (B)-(I), (C)-(IV), (D)-(III)

D

(A)-(II), (B)-(I), (C)-(III), (D)-(IV)

Question 37: Palette 37/130

JEE Mains 2025 MCQ

A liquid when kept inside a thermally insulated closed vessel at $25^{\circ} \mathrm{C}$ was mechanically stirred from outside. What will be the correct option for the following thermodynamic parameters ?

A

$\Delta \mathrm{U}=0, \mathrm{q}<0, \mathrm{w}>0$

B

$\Delta \mathrm{U}>0, \mathrm{q}=0, \mathrm{w}>0$

C

$\Delta \mathrm{U}=0, \mathrm{q}=0, \mathrm{w}=0$

D

$\Delta \mathrm{U}<0, \mathrm{q}=0, \mathrm{w}>0$

Question 38: Palette 38/130

JEE Mains 2024 MCQ

Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R)

Assertion (A) : Enthalpy of neutralisation of strong monobasic acid with strong monoacidic base is always $-57 \mathrm{~kJ} \mathrm{~mol}^{-1}$

Reason (R) : Enthalpy of neutralisation is the amount of heat liberated when one mole of $\mathrm{H}^{+}$ ions furnished by acid combine with one mole of ${ }^{-} \mathrm{OH}$ ions furnished by base to form one mole of water.

In the light of the above statements, choose the correct answer from the options given below.

A

(A) is true but (R) is false

B

Both (A) and (R) are true and (R) is the correct explanation of (A)

C

Both (A) and (R) are true but (R) is not the correct explanation of (A)

D

(A) is false but (R) is true

Question 39: Palette 39/130

JEE Mains 2024 MCQ

Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following :

A

$\mathrm{q}=0, \Delta \mathrm{T}=0, \mathrm{w}=0$

B

$\mathrm{q}=0, \Delta \mathrm{T} \neq 0, \mathrm{w}=0$

C

$\mathrm{q} \neq 0, \Delta \mathrm{T}=0, \mathrm{w}=0$

D

$\mathrm{q}=0, \Delta \mathrm{T}<0, \mathrm{w} \neq 0$

Question 40: Palette 40/130

JEE Mains 2024 MCQ

Which of the following is not correct?

A

$\Delta \mathrm{G}$ is positive for a spontaneous reaction

B

$\Delta \mathrm{G}$ is positive for a non-spontaneous reaction

C

$\Delta \mathrm{G}$ is zero for a reversible reaction

D

$\Delta \mathrm{G}$ is negative for a spontaneous reaction

Question 41: Palette 41/130

JEE Mains 2023 MCQ

What happens when methane undergoes combustion in systems A and B respectively?

A

System A	System B
Temperature falls	Temperature rises

B

System A	System B
Temperature rises	Temperature remains same

C

System A	System B
Temperature falls	Temperature remains same

D

System A	System B
Temperature remains same	Temperature rises

Question 42: Palette 42/130

JEE Mains 2023 MCQ

Given

(A)	$\mathrm{2CO(g)+O_2(g)\to 2CO_2(g)}$		$\mathrm{\Delta H_1^0=-x~kJ~mol^{-1}}$
(B)	$\mathrm{C(graphite)+O_2(g)\to CO_2(g)}$		$\mathrm{\Delta H_2^0=-y~kJ~mol^{-1}}$

$\mathrm{\Delta H^0}$ for the reaction

$\mathrm{C(graphite)+\frac{1}{2}O_2(g)\to CO(g)}$ is :

A

$\frac{x-2y}{2}$

B

$\frac{x+2y}{2}$

C

$2y-x$

D

$\frac{2x-y}{2}$

Question 43: Palette 43/130

JEE Mains 2023 MCQ

Which of the following relations are correct?

(A) $\mathrm{\Delta U=q+p\Delta V}$

(B) $\mathrm{\Delta G=\Delta H-T\Delta S}$

(C) $\Delta \mathrm{S}=\frac{q_{rev}}{T}$

(D) $\mathrm{\Delta H=\Delta U-\Delta nRT}$

Choose the most appropriate answer from the options given below :

A

A and B only

B

B and C only

C

C and D only

D

B and D only

Question 44: Palette 44/130

JEE Mains 2022 MCQ

Given below are two statements: One is labelled as Assertion $\mathbf{A}$ and the other is labelled as Reason $\mathbf{R}$

Assertion A : The reduction of a metal oxide is easier if the metal formed is in liquid state than solid state.

Reason $\mathbf{R}$ : The value of $\Delta G ^\Theta$ becomes more on negative side as entropy is higher in liquid state than solid state.

In the light of the above statements, choose the most appropriate answer from the options given below

A

Both A and R are correct and R is the correct explanation of A

B

Both A and R are correct but R is NOT the correct explanation of A

C

A is correct but R is not correct

D

A is not correct but R is correct

Question 45: Palette 45/130

JEE Mains 2022 MCQ

Which of the following relation is not correct?

A

$\Delta \mathrm{H}=\Delta \mathrm{U}-\mathrm{P} \Delta \mathrm{V}$

B

$\Delta \mathrm{U}=\mathrm{q}+\mathrm{W}$

C

$\Delta \mathrm{S}_{\text {sys }}+\Delta \mathrm{S}_{\text {surr }} \geqslant 0$

D

$\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S}$

Question 46: Palette 46/130

JEE Mains 2022 MCQ

$\Delta$G$^\circ$ vs T plot for the formation of MgO, involving reaction

2Mg + O₂ $\to$ 2MgO, will look like :

A

B

C

D

Question 47: Palette 47/130

JEE Mains 2022 MCQ

Match List-I with List-II.

	List - I		List - II
(A)	Spontaneous process	(I)	$\Delta H < 0$
(B)	Process with $\Delta P = 0$, $\Delta T = 0$	(II)	$\Delta {G_{T,P}} < 0$
(C)	$\Delta {H_{reaction}}$	(III)	Isothermal and isobaric process
(D)	Exothermic Process	(IV)	[Bond energies of molecules in reactants] $ - $ [Bond energies of product molecules

Choose the correct answer from the options given below :

A

(A) - (III), (B) - (II), (C) - (IV), (D) - (I)

B

(A) - (II), (B) - (III), (C) - (IV), (D) - (I)

C

(A) - (II), (B) - (III), (C) - (I), (D) - (IV)

D

(A) - (II), (B) - (I), (C) - (III), (D) - (IV)

Question 48: Palette 48/130

JEE Mains 2022 MCQ

At 25$^\circ$C and 1 atm pressure, the enthalpy of combustion of benzene (I) and acetylene (g) are $-$ 3268 kJ mol^$-$1 and $-$1300 kJ mol^$-$1, respectively. The change in enthalpy for the reaction 3 C₂H₂(g) $\to$ C₆H₆ (I), is :

A

+324 kJ mol^$-$1

B

+632 kJ mol^$-$1

C

$-$ 632 kJ mol^$-$1

D

$-$ 732 kJ mol^$-$1

Question 49: Palette 49/130

JEE Mains 2022 MCQ

At 25$^\circ$C and 1 atm pressure, the enthalpies of combustion are as given below :

Substance	${H_2}$	C (graphite)	${C_2}{H_6}(g)$
${{{\Delta _c}{H^\Theta }} \over {kJ\,mo{l^{ - 1}}}}$	$ - 286.0$	$ - 394.0$	$ - 1560.0$

The enthalpy of formation of ethane is

A

+54.0 kJ mol^$-$1

B

$-$68.0 kJ mol^$-$1

C

$-$86.0 kJ mol^$-$1

D

+97.0 kJ mol^$-$1

Question 50: Palette 50/130

JEE Mains 2021 MCQ

The incorrect expression among the following is :

A

${{\Delta {G_{System}}} \over {\Delta {S_{Total}}}} = - T$ (at constant P)

B

$K = {{\Delta H^\circ - T\Delta S^\circ } \over {RT}}$

C

$K = {e^{ - \Delta G^\circ /RT}}$

D

For isothermal process ${w_{reversible}} = - nRT\ln {{{V_f}} \over {{V_i}}}$

Question 51: Palette 51/130

JEE Mains 2021 MCQ

During which of the following processes, does entropy decrease?

(A) Freezing of water to ice at 0$^\circ$C

(B) Freezing of water to ice at $-$10$^\circ$C

(C) N₂(g) + 3H₂(g) $ \to $ 2NH₃(g)

(D) Adsorption of CO(g) on lead surface.

(E) Dissolution of NaCl in water

Choose the correct answer from the options given below :

A

(A), (C) and (E) only

B

(B) and (C) only

C

(A), (B), (C) and (D) only

D

(A) and (E) only

Question 52: Palette 52/130

JEE Mains 2020 MCQ

For a reaction,
4M(s) + nO₂(g) $ \to $ 2M₂O_n(s)
the free energy change is plotted as a function of temperature. The temperature below which the oxide is stable could be inferred from the plot as the point at which :

A

the free energy change shows a change from negative to positive value

B

the slope changes from positive to negative

C

the slope changes from negative to positive

D

the slope changes from positive to zero

Question 53: Palette 53/130

JEE Mains 2020 MCQ

Lattice enthalpy and enthalpy of solution of NaCl are 788 kJ mol^–1, and 4 kJ mol^–1, respectively.
The hydration enthalpy of NaCl is :

A

–780 kJ mol^–1

B

–784 kJ mol^–1

C

780 kJ mol^–1

D

784 kJ mol^–1

Question 54: Palette 54/130

JEE Mains 2020 MCQ

Five moles of an ideal gas at 1 bar and 298 K is expanded into vacuum to double the volume. The work done is :

A

Zero

B

-RT $\ln {{{V_2}} \over {{V_1}}}$

C

C_V (T₂ – T₁)

D

– RT (V₂ – V₁)

Question 55: Palette 55/130

JEE Mains 2020 MCQ

The process that is NOT endothermic in nature is :

A

Ar(g) + e^- $ \to $ Ar^-(g)

B

H(g) + e^- $ \to $ H^-(g)

C

Na(g) $ \to $ Na⁺(g) + e^-

D

O^-(g) + e^- $ \to $ O^2-(g)

Question 56: Palette 56/130

JEE Mains 2020 MCQ

For one mole of an ideal gas, which of these statements must be true?
(a) U and H each depends only on temperature
(b) Compressibility factor z is not equal to 1
(c) C_{P, m} – C_{V, m} = R
(d) dU = C_VdT for any process

A

(a), (c) and (d)

B

(a) and (c)

C

(c) and (d)

D

(b), (c) and (d)

Question 57: Palette 57/130

JEE Mains 2020 MCQ

The true statement amongst the following is :

A

S is a function of temperature but $\Delta $S is not a function of temperature.

B

Both S and $\Delta $S are not functions of temperature.

C

Both $\Delta $S and S are functions of temperature.

D

S is not a function of temperature but $\Delta $S is a function of temperature.

Question 58: Palette 58/130

JEE Mains 2020 MCQ

If enthalpy of atomisation for Br₂₍₁₎ is x kJ/mol and bond enthalpy for Br₂ is y kJ/mol, the relation between them :

A

does not exist

B

is x < y

C

is x > y

D

is x = y

Question 59: Palette 59/130

JEE Mains 2019 MCQ

An ideal gas is allowed to expand form 1 L to 10 L against a constant external pressure of I bar. The work done in kJ is :

A

+10.0

B

–0.9

C

– 2.0

D

– 9.0

Question 60: Palette 60/130

JEE Mains 2019 MCQ

Enthalpy of sublimation of iodine is 24 cal g^–1 at 200 ^oC. If specific heat of I₂(s) and l₂ (vap) are 0.055 and 0.031 cal g^–1K ^–1 respectively, then enthalpy of sublimation of iodine at 250 ^oC in cal g^–1 is :

A

2.85

B

22.8

C

11.4

D

5.7

Question 61: Palette 61/130

JEE Mains 2019 MCQ

The difference between $\Delta $H and $\Delta $U ($\Delta $H – $\Delta $U), when the combustion of one mole of heptane(l) is carried out at a temperature T, is equal to :

A

– 4 RT

B

3 RT

C

– 3 RT

D

4 RT

Question 62: Palette 62/130

JEE Mains 2019 MCQ

A process will be spontaneous at all temperatures if :

A

$\Delta $H < 0 and $\Delta $S > 0

B

$\Delta $H < 0 and $\Delta $S < 0

C

$\Delta $H > 0 and $\Delta $S < 0

D

$\Delta $H > 0 and $\Delta $S > 0

Question 63: Palette 63/130

JEE Mains 2019 MCQ

During compression of a spring the work done is 10kJ and 2kJ escaped to the surroundings as heat. The change in internal energy, $\Delta $U(inkJ) is :

A

- 12

B

8

C

- 8

D

12

Question 64: Palette 64/130

JEE Mains 2019 MCQ

Among the following, the set of parameters that represents path function, is :
(A) q + w
(B) q
(C) w
(D) H–TS

A

(B) and (C)

B

(A) and (D)

C

(B), (C) and (D)

D

(A), (B) and (C)

Question 65: Palette 65/130

JEE Mains 2019 MCQ

5 moles of an ideal gas at 100 K are allowed to undergo reversible compression till its temperature becomes 200 K. If C_V = 28 JK^–1mol^–1, calculate $\Delta $U and $\Delta $pV for this process. (R = 8.0 JK^–1 mol^–1]

A

$\Delta $U = 14 kJ; $\Delta $(pV) = 4 kJ

B

$\Delta $U = 2.8 kJ; $\Delta $(pV) = 0.8 kJ

C

$\Delta $U = 14 kJ; $\Delta $(pV) = 18 kJ

D

$\Delta $U = 14 kJ; $\Delta $(pV) = 0.8 kJ

Question 66: Palette 66/130

JEE Mains 2019 MCQ

Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas? (Assume non-expansion work is zero)

A

Adiabatic process : $\Delta $U= – w

B

Cyclic process : q = –w

C

Isochoric process : $\Delta $U= q

D

Isothermal process : q = – w

Question 67: Palette 67/130

JEE Mains 2019 MCQ

For silver, C_p(J K^–1 mol^–1) = 23 +0.01 T. If the temperature (T) of 3 moles of silver is raised from 300 K to 1000 K at 1 atm pressure, the value of $\Delta H$ will be close to :

A

62 KJ

B

16 KJ

C

13 KJ

D

21 KJ

Question 68: Palette 68/130

JEE Mains 2019 MCQ

Given

(i)  C (graphite) + O₂(g) $ \to $ CO₂(g); $\Delta $rH$^\Theta $ = x kJ mol^$-$1

(ii)  C(graphite) + ${1 \over 2}$O₂(g) $ \to $ CO(g); $\Delta $rH$^\Theta $ = y kJ mol^$-$1

(iii)  CO(g) + ${1 \over 2}$ O₂(g) $ \to $ CO₂(g); $\Delta $rH$^\Theta $ = z kJ mol^$-$1

Based on the above thermochemical equations, find out which one of the following algebraic relationships is correct?

A

z = x + y

B

x = y + z

C

x = y – z

D

y = 2z – x

Question 69: Palette 69/130

JEE Mains 2019 MCQ

The combination of plots which does not represent isothermal expansion of an ideal gas is –

A

A and D

B

B and D

C

B and C

D

A and C

Question 70: Palette 70/130

JEE Mains 2019 MCQ

For diatomic ideal gas in a closed system, which of the following plots does not correctly describe the relation between various thermodynamic quantities?

A

B

C

D

Question 71: Palette 71/130

JEE Mains 2019 MCQ

The reaction, MgO(s) + C(s) $ \to $ Mg(s) + CO(g), for which $\Delta $_rH^o + 491.1 kJ mol^–1 and $\Delta $_rS^o = 198.0 JK^–1 mol^–1, is not feasible at 298 K. Temperature above which reaciton will be feasible is :

A

2480.3 K

B

2040.5 K

C

2380.5 K

D

1890.0 K

Question 72: Palette 72/130

JEE Mains 2019 MCQ

For the equilibrium,
2H₂O $\rightleftharpoons$ H₃O⁺ + OH^$-$, the value of $\Delta $G^o at 298 K is approximately :

A

$-$ 80 kJ mol^–1

B

100 kJ mol^$-$1

C

$-$ 100 kJ mol^$-$1

D

80 kJ mol^–1

Question 73: Palette 73/130

JEE Mains 2019 MCQ

The standard reaction Gibbs energy for a chemical reaction at an absolute temperature T is given by $\Delta $_rG^o = A – BT

Where A and B are non-zero constants. Which of the following is TRUE about this reaction?

A

Exothermic if B < 0

B

Endothermic if A > 0

C

Exothermic if A > 0 and B < 0

D

Endothermic if A < 0 and B > 0

Question 74: Palette 74/130

JEE Mains 2019 MCQ

For the chemical reaction X $\rightleftharpoons$ Y, the standard reaction Gibbs energy depends on temperature T (in K) as $\Delta $_rG^o (in kJ mol^–1) = 120 $ - {3 \over 8}$ T.

The major component of the reaction mixture at T is :

A

Y if T = 300 K

B

Y if T = 280 K

C

X if T = 350 K

D

X if T = 315 K

Question 75: Palette 75/130

JEE Mains 2019 MCQ

Two blocks of the same metal having same mass and at temperature T₁ and T₂, respectively, are brought in contact with each other and allowed to attain thermal equilibrium at constant pressure. The change in entropy, $\Delta $S, for this process is :

A

2C_p In $\left[ {{{{{\left( {{T_1} + {T_2}} \right)}^{{1 \over 2}}}} \over {{T_1}{T_2}}}} \right]$

B

2C_p In $\left[ {{{\left( {{T_1} + {T_2}} \right)} \over {2{T_1}{T_2}}}} \right]$

C

C_p In $\left[ {{{{{\left( {{T_1} + {T_2}} \right)}^2}} \over {4{T_1}{T_2}}}} \right]$

D

2C_p In $\left[ {{{\left( {{T_1} + {T_2}} \right)} \over {4{T_1}{T_2}}}} \right]$

Question 76: Palette 76/130

JEE Mains 2019 MCQ

The process with negative entropy change is :

A

Dissociation of CaSO₄ (s) to CaO(s) and SO₃(g)

B

Dissolution of iodine in water

C

Synthesis of ammonia from N₂ and H₂

D

Sublimation of dry ice

Question 77: Palette 77/130

JEE Mains 2019 MCQ

An ideal gas undergoes isothermal compression from 5m³ to 1 m³ against a constant external pressure of 4 Nm^–2. Heat released in this process is used to increase the temperature of 1 mole of Al. If molar heat capacity of Al is 24 J mol^–1 K^–1, the temperature of Al increases by :

A

${2 \over 3}K$

B

${3 \over 2}K$

C

1 K

D

2 K

Question 78: Palette 78/130

JEE Mains 2019 MCQ

A process has $\Delta $H = 200 J mol^–1 and $\Delta $S = 40 JK^–1 mol^–1. Out of the values given below, choose the minimum temperature above which the process will be spontaneous :

A

4 K

B

20 K

C

5 K

D

12 K

Question 79: Palette 79/130

JEE Mains 2019 MCQ

The entropy change associated with the conversion of 1 kg of ice at 273 K to water vapours at 383 K is :

(Specific heat of water liquid and water vapour are 4.2 kJ K^$-$1 kg^$-$1 and 2.0 kJ K^$-$1 kg^$-$1; heat of liquid fusion and vapourisation of water are 334 kJ^$-$1 and 2491 kJ kg^$-$1, respectively). (log 273 = 2.436, log 373 = 2.572, log 383 = 2.583)

A

7.90 kJ kg^$-$1 K^$-$1

B

2.64 kJ kg^$-$1 K^$-$1

C

8.49 kJ kg^$-$1 K^$-$1

D

9.26 kJ kg^$-$1 K^$-$1

Question 80: Palette 80/130

JEE Mains 2019 MCQ

Consider the reversible isothermal expansion of an ideal gas in a closed system at two different temperatures T₁ and T₂ (T₁ < T₂). The correct graphical depiction of the dependence of work done (w) on the final volume (V) is :

A

B

C

D

Question 81: Palette 81/130

JEE Mains 2018 MCQ

For which of the following processes, $\Delta $S is negative ?

A

H₂(g) $ \to $ 2H(g)

B

N₂(g, 1 atm) $ \to $ N₂(g, 5 atm)

C

C(diamond) $ \to $ C(graphite)

D

N₂(g, 273 K) $ \to $ N₂(g, 300 K)

Question 82: Palette 82/130

JEE Mains 2018 MCQ

At 320 K, a gas A₂ is 20% dissociated to A(g). The standard free energy change at 320 K and 1 atm in J mol^-1 is approximately : (R = 8.314 JK^-1 mol^-1; ln2 = 0.693; ln 3 = 1.098)

A

4763

B

2068

C

1844

D

4281

Question 83: Palette 83/130

JEE Mains 2018 MCQ

Which of the following lines correctly show the temperature dependence of equilibrium constant K, for an exothermic reaction?

A

A and D

B

A and B

C

B and C

D

C and D

Question 84: Palette 84/130

JEE Mains 2018 MCQ

The combustion of benzene(l) gives CO₂(g) and H₂O(l). Given that heat of combustion of benzene at constant volume is –3263.9 kJ mol^–1 at 25^oC; heat of combustion (in kJ mol^–1) of benzene at constant pressure will be :
(R = 8.314 JK^–1 mol^–1)

A

–3267.6

B

4152.6

C

–452.46

D

3260

Question 85: Palette 85/130

JEE Mains 2018 MCQ

Given

(i)   2Fe₂O₃(s) $ \to $ 4Fe(s) + 3O₂(g);

$\Delta $_rG^o = + 1487.0 kJ mol^-1

(ii)   2CO(g) + O₂(g) $ \to $ 2CO₂(g);

$\Delta $_rG^o = $-$ 514.4 kJ mol^-1

Free energy change, $\Delta $_rG^o for the reaction

2Fe₂O₃(s) + 6CO(g) $ \to $ 4Fe(s) + 6CO₂(g) will be :

A

$-$ 112.4 kJ mol^-1

B

$-$ 56.2 kJ mol^-1

C

$-$ 168.2 kJ mol^-1

D

$-$ 208.0 kJ mol^-1

Question 86: Palette 86/130

JEE Mains 2018 MCQ

$\Delta $_fG^o at 500 K for substance 'S' in liquid state and gaseous state are +100.7 kcl mol-¹ and +103 kcal mol^-1, respectively. Vapour pressure of liquid 'S' at 500 K is approximately equal to : ( R = 2 cal K^-1 mol^-1 )

A

0.1 atm

B

1 atm

C

10 atm

D

100 atm

Question 87: Palette 87/130

JEE Mains 2018 MCQ

An ideal gas undergoes a cyclic process as shown in Figure.


$\Delta $U_BC = $-$5 kJ mol^-1, q_AB = $2$ kJ mol^-1, W_AB = $-$5 kJ mol^-1, W_CA = 3 kJ mol^-1. Heat absorbed by the system during process $CA$ is :

A

$-$5 kJ mol^-1

B

+5 kJ mol^-1

C

18 kJ mol^-1

D

$-$18 kJ mol^-1

Question 88: Palette 88/130

JEE Mains 2018 MCQ

For which of the following reactions, $\Delta $H is equal to $\Delta $U?

A

N₂(g) + 3H₂(g) $ \to $ 2NH₃(g)

B

2HI(g) $ \to $ H₂(g) + I₂(g)

C

2NO₂(g) $ \to $ N₂O₄(g)

D

2SO₂(g) + O₂(g) $ \to $ 2SO₃(g)

Question 89: Palette 89/130

JEE Mains 2017 MCQ

A gas undergoes change from state A to state B. In this process, the heat absorbed and work done by the gas is 5 J and 8 J, respectively. Now gas is brought back to A by another process during which 3 J of heat is evolved. In this reverse process of B to A :

A

10 J of the work will be done by the gas.

B

6 J of the work will be done by the gas.

C

10 J of the work will be done by the surrounding on gas.

D

6 J of the work will be done by the surrounding on gas.

Question 90: Palette 90/130

JEE Mains 2017 MCQ

An ideal gas undergoes isothermal expansion at constant pressure. During the process :

A

enthalpy increases but entropy decreases.

B

enthalpy remains constant but entropy increases.

C

enthalpy decreases but entropy increases.

D

Both enthalpy and entropy remain constant.

Question 91: Palette 91/130

JEE Mains 2017 MCQ

The enthalpy change on freezing of 1 mol of water at 5^oC to ice at −5^oC is :

(Given $\Delta $_fusH = 6 kJ mol^$-$1 at 0^oC,
C_p(H₂O, $\ell $ = 75.3J mol^$-$1 K^$-$1)
C_p(H₂O s) =36.8 J mol^$-$1 K^$-$1)

A

5.44 kJ mol^$-$1

B

5.81 kJ mol^$-$1

C

6.56 kJ mol^$-$1

D

6.00 kJ mol^$-$1

Question 92: Palette 92/130

JEE Mains 2017 MCQ

For a reaction, A(g) $ \to $ A($\ell $); $\Delta $H= $-$ 3RT.
The correct statement for the reaction is :

A

$\Delta $H = $\Delta $U $ \ne $ O

B

$\Delta $H = $\Delta $U = O

C

$\left| {} \right.$$\Delta $H$\left| {} \right.$ < $\left| {} \right.$$\Delta $U$\left| {} \right.$

D

$\left| {} \right.$$\Delta $H$\left| {} \right.$ > $\left| {} \right.$$\Delta $U$\left| {} \right.$

Question 93: Palette 93/130

JEE Mains 2017 MCQ

$\Delta $U is equal to :

A

Isobaric work

B

Adiabatic work

C

Isothermal work

D

Isochoric work

Question 94: Palette 94/130

JEE Mains 2017 MCQ

Given, ${C_{(graphite)}} + {O_2} \to C{O_2}(g)$;

${\Delta _r}{H^o}$ = - 393.5 kJ mol^-1

${{\rm H}_2}(g)$ + ${1 \over 2}{O_2}(g)$$\to {{\rm H}_2}{\rm O}(l)$

${\Delta _r}{H^o}$ = - 285.8 kJ mol^-1

$C{O_2}(g)$ + $2{{\rm H}_2}{\rm O}(l) \to$ $C{H_4}(g)$ + $2{O_2}(g)$

${\Delta _r}{H^o}$ = + 890.3 kJ mol^-1

Based on the above thermochemical equations, the value of ${\Delta _r}{H^o}$ at 298 K for the reaction

${C_{(graphite)}}$ + $2{{\rm H}_2}(g) \to$ $C{H_4}(g)$ will be :

A

+144.0 kJ mol^–1

B

– 74.8 kJ mol^–1

C

-144.0 kJ mol^–1

D

+ 74.8 kJ mol^–1

Question 95: Palette 95/130

JEE Mains 2016 MCQ

If 100 mole of H₂O₂ decompose at 1 bar and 300 K, the work done (kJ) by one mole of O₂(g) as it expands against 1 bar pressure is :

2H₂O₂(l)    $\rightleftharpoons$    2H₂O(l) + O₂(g)

(R = 8.3 J K ^$-$1 mol^$-$1)

A

62.25

B

124.50

C

249.00

D

498.00

Question 96: Palette 96/130

JEE Mains 2016 MCQ

The plot shows the variation of −$ln$ K_p versus temperature for the two reactions.

M(s) + ${1 \over 2}$ O₂(g) $ \to $ MO(s) and

C(s) + ${1 \over 2}$ O₂(g) $ \to $ CO(s)


Identify the correct statement :

A

At T > 1200 K, carbon will reduce MO(s) to M(s).

B

At T < 1200 K, the reaction

MO(s) + C(s) $ \to $ M(s) + CO(g) is spontaneous.

C

At T < 1200 K, oxidation of carbon is unfavourable

D

Oxidation of carbon is favourable at all temperatures.

Question 97: Palette 97/130

JEE Mains 2016 MCQ

A reaction at 1 bar is non-spontaneous at low temperature but becomes spontaneous at high temperature. Identify the correct statement about the reaction among the following :

A

Both $\Delta $H and $\Delta $S are negative.

B

Both $\Delta $H and $\Delta $S are positive.

C

$\Delta $H is positive while $\Delta $S is negative.

D

$\Delta $H is negative while $\Delta $S is positive.

Question 98: Palette 98/130

JEE Mains 2016 MCQ

For the reaction,
A(g) + B(g) $ \to $ C(g) + D(g), $\Delta $H^o and $\Delta $S^o are, respectively, − 29.8 kJ mol⁻¹ and −0.100 kJ K⁻¹ mol⁻¹ at 298 K. The equilibrium constant for the reaction at 298 K is :

A

1.0 $ \times $ 10^$-$10

B

1.0 $ \times $ 10¹⁰

C

10

D

1

Question 99: Palette 99/130

JEE Mains 2016 MCQ

The heats of combustion of carbon and carbon monoxide are –393.5 and –283.5 kJ mol^–1, respectively. The heat of formation (in kJ) of carbon monoxide per mole is :

A

676.5

B

-676.5

C

–110

D

110.5

Question 100: Palette 100/130

JEE Mains 2015 MCQ

The following reaction is performed at 298 K
2NO(g) + O₂ (g) $\leftrightharpoons$ 2NO₂ (g)
The standard free energy of formation of NO(g) is 86.6 kJ/mol at 298 K. What is the standard free energy of formation of NO₂(g) at 298 K? (KP = 1.6 × 10¹²)

A

86600 + R(298) ln(1.6 $\times$ 10¹²)

B

86600 - $ln (1.6 \times 10^{12}) \over R (298)$

C

0.5[2×86,600 – R(298) ln(1.6×10¹²)]

D

R(298) ln(1.6×10¹²) – 86600

Question 101: Palette 101/130

JEE Mains 2014 MCQ

For complete combustion of ethanol, C₂H₅OH(l) + 3O₂(g) $\to$ 2CO₂(g) + 3H₂O(l) the amount of heat produced as measured in bomb calorimeter, is 1364.47 kJ mol^–1 at 25^oC. Assuming ideality the Enthalpy of combustion, $\Delta _CH$, for the reaction will be : (R = 8.314 kJ mol^–1)

A

–1460.50 kJ mol^–1

B

– 1350.50 kJ mol^–1

C

– 1366.95 kJ mol^–1

D

– 1361.95 kJ mol^–1

Question 102: Palette 102/130

JEE Mains 2013 MCQ

A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 37.0^oC. As it does so, it absorbs 208J of heat. The values of q and w for the process will be :
(R = 8.314 J/mol K) ( l n 7.5 = 2.01)

A

q = – 208 J, w = – 208 J

B

q = – 208 J, w = + 208 J

C

q = + 208 J, w = + 208 J

D

q = + 208 J, w = – 208 J

Question 103: Palette 103/130

JEE Mains 2012 MCQ

The incorrect expression among the following is :

A

${{\Delta {G_{system}}} \over {\Delta {S_{total}}}} = - T$

B

In isothermal process ${w_{reversible}}$ = $ - nRT\,\ln \,{{{V_f}} \over {{V_i}}}$

C

In $K\, = {{\Delta {H^o} - T\Delta {S^o}} \over {RT}}$

D

$K\, = \,{e^{ - \Delta {G^o}/RT}}$

Question 104: Palette 104/130

JEE Mains 2011 MCQ

The entropy change involved in the isothermal reversible expansion of 2 moles of an ideal gas from a volume of 10 dm³ to a volume of 100 dm³ at 27^oC is :

A

35.8 J mol^-1 K⁻¹

B

32.3 J mol^-1 K⁻¹

C

42.3 J mol^-1 K⁻¹

D

38.3 J mol^-1 K⁻¹

Question 105: Palette 105/130

JEE Mains 2010 MCQ

For a particular reversible reaction at temperature T, ∆H and ∆S were found to be both +ve. If T_e is the temperature at equilibrium, the reaction would be spontaneous when :

A

T_e > T

B

T > T_e

C

T_e is 5 times T

D

T = T_e

Question 106: Palette 106/130

JEE Mains 2010 MCQ

The standard enthalpy of formation of NH₃ is –46.0 kJ mol^–1. If the enthalpy of formation of H₂ from its atoms is –436 kJ mol^–1 and that of N2 is –712 kJ mol^–1, the average bond enthalpy of N–H bond in NH₃ is :

A

–964 kJ mol^–1

B

+352 kJ mol^–1

C

+ 1056 kJ mol^–1

D

–1102 kJ mol^–1

Question 107: Palette 107/130

JEE Mains 2009 MCQ

On the basis of the following thermochemical data :
($\Delta _fG^oH^+_{(aq)}$ = 0)

H₂O(l) $\to$ H⁺(aq) + OH^-(aq); $\Delta H$ = 57.32 kJ
H₂(g) + ${1 \over 2} O_2(g) \to$ H₂O(l); $\Delta H$ = -286.20 kJ

The value of enthalpy of formation of OH⁻ ion at 25^oC is :

A

-22.88 kJ

B

-228.88 kJ

C

+228.88 kJ

D

-343.52 kJ

Question 108: Palette 108/130

JEE Mains 2008 MCQ

Standard entropy of X₂, Y₂ and XY₃ are 60, 40 and 50 JK⁻¹ mol⁻¹ , respectively. For the reaction,
${1 \over 2} X_2$ + ${3 \over 2} Y_2 \to$ XY₃, $\Delta H$ = -30 kJ, to be at equilibrium, the temperature will be :

A

1250 K

B

500 K

C

750 K

D

1000 K

Question 109: Palette 109/130

JEE Mains 2008 MCQ

Oxidising power of chlorine in aqueous solution can be determined by the parameters indicated below:
${1 \over 2}C{l_2}(g)$ $\buildrel {{1 \over 2}{\Delta _{diss}}{H^\Theta }} \over \longrightarrow $ $Cl(g)$ $\buildrel {{\Delta _{eg}}{H^\Theta }} \over \longrightarrow $ $C{l^ - }(g)$ $\buildrel {{\Delta _{Hyd}}{H^\Theta }} \over \longrightarrow $ $C{l^ - }(aq)$
(Using the data, ${\Delta _{diss}}H_{C{l_2}}^\Theta $ = 240 kJ/mol, ${\Delta _{eg}}H_{Cl}^\Theta $ = -349 kJ/mol, ${\Delta _{hyd}}H_{C{l^ - }}^\Theta $ = - 381 kJ/mol) will be :

A

+152 kJ mol⁻¹

B

−610 kJ mol⁻¹

C

−850 kJ mol⁻¹

D

+120 kJ mol⁻¹

Question 110: Palette 110/130

JEE Mains 2007 MCQ

Assuming that water vapour is an ideal gas, the internal energy change $\left( {\Delta U} \right)$ when $1$ mol of water is vapourised at $1$ bar pressure and ${100^ \circ }C$ (Given : molar enthalpy of vapourisation of water at $1$ bar and $373$ $K$ $ = 41\,kJ\,mo{l^{ - 1}}\,$
and $R = 8.3\,J\,mo{l^{ - 1}}\,{K^{ - 1}}$ )

A

$41.00\,kJ\,mo{l^{ - 1}}$

B

$4.100\,kJ\,mo{l^{ - 1}}$

C

$3.7904\,kJ\,mo{l^{ - 1}}$

D

$37.904\,kJ\,mo{l^{ - 1}}$

Question 111: Palette 111/130

JEE Mains 2007 MCQ

In conversion of lime-stone to lime,
CaCO₃(s) $\to$ CaO(s) + CO₂ (g) the vales of ∆H° and ∆S° are +179.1 kJ mol−1 and 160.2 J/K respectively at 298 K and 1 bar. Assuming that ∆H° do not change with temperature, temperature above which conversion of limestone to lime will be spontaneous is :

A

1008 K

B

1200

C

845 K

D

1118 K

Question 112: Palette 112/130

JEE Mains 2007 MCQ

Identify the correct statement regarding a spontaneous process :

A

For a spontaneous process in an isolated system, the change in entropy is positive

B

Endothermic processes are never spontaneous

C

Exothermic processes are always spontaneous

D

Lowering of energy in the reaction process is the only criterion for spontaneity

Question 113: Palette 113/130

JEE Mains 2006 MCQ

The enthalpy changes for the following processes are listed below :

Cl₂(g) = 2Cl(g), 242.3 kJ mol^–1
I₂(g) = 2I(g), 151.0 kJ mol^–1
ICl(g) = I(g) + Cl(g), 211.3 kJ mol^–1
I₂(s) = I₂(g), 62.76 kJ mol^–1

Given that the standard states for iodine and chlorine are I₂(s) and Cl₂(g), the standard enthalpy of formation for ICl(g) is :

A

–14.6 kJ mol^–1

B

–16.8 kJ mol^–1

C

+16.8 kJ mol^–1

D

+244.8 kJ mol^–1

Question 114: Palette 114/130

JEE Mains 2006 MCQ

An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If T_i is the initial temperature and T_f is the final temperature, which of the following statements is correct?

A

(T_f)_irrev > (T_f)_rev

B

(T_f)_rev = (T_f)_irrev

C

T_f > T_i for reversible process but T_f = T_i for irreversible process

D

T_f = T_i for both reversible and irreversible processes

Question 115: Palette 115/130

JEE Mains 2006 MCQ

The standard enthalpy of formation $\Delta _fH^o$ at 298 K for methane, CH₄(g), is –74.8 kJ mol^–1. The additional information required to determine the average energy for C – H bond formation would be :

A

the dissociation energy of H₂ and enthalpy of sublimation of carbon

B

latent heat of vapourization of methane

C

the first four ionization energies of carbon and electron gain enthalpy of hydrogen

D

the dissociation energy of hydrogen molecule, H₂

Question 116: Palette 116/130

JEE Mains 2006 MCQ

($\Delta H - \Delta U$) for the formation of carbon monoxide (CO) from its elements at 298 K is : (R = 8.314 J K^–1 mol^–1)

A

–1238.78 J mol^–1

B

1238.78 J mol^–1

C

–2477.57 J mol^–1

D

2477.57 J mol^–1

Question 117: Palette 117/130

JEE Mains 2005 MCQ

If the bond dissociation energies of XY, X₂ and Y₂ (all diatomic molecules) are in the ratio of 1:1:0.5 and $\Delta H_f$ for the formation of XY is -200 kJ mole^-1. The bond dissociation energy of X₂ will be :

A

100 kJ mol^-1

B

200 kJ mol^-1

C

300 kJ mol^-1

D

800 kJ mol^-1

Question 118: Palette 118/130

JEE Mains 2005 MCQ

Consider the reaction: N₂ + 3H₂ $\to$ 2NH₃ carried out at constant temperature and pressure. If $\Delta H$ and $\Delta U$ are the enthalpy and internal energy changes for the reaction, which of the following expressions is true?

A

$\Delta H$ > $\Delta U$

B

$\Delta H$ < $\Delta U$

C

$\Delta H$ = $\Delta U$

D

$\Delta H$ = 0

Question 119: Palette 119/130

JEE Mains 2005 MCQ

Consider an endothermic reaction, X $\to$ Y with the activation energies E_b and E_f for the backward and forward reactions, respectively. In general :

A

E_b < E_f

B

E_b > E_f

C

E_b = E_f

D

There is no definite relation between E_b and E_f

Question 120: Palette 120/130

JEE Mains 2004 MCQ

An ideal gas expands in volume from 1$\times$10^-3 m³ to 1 $\times$ 10^-2 m³ at 300 K against a constant pressure of 1$\times$10⁵ Nm^-2. The work done is :

A

-900 J

B

900 kJ

C

270 kJ

D

-900 kJ

Question 121: Palette 121/130

JEE Mains 2004 MCQ

The enthalpies of combustion of carbon and carbon monoxide are -393.5 and -283 kJ mol-1 respectively. The enthalpy of formation of carbon monoxide per mole is :

A

110.5 kJ

B

-110.5 kJ

C

-676.5 kJ

D

676.5 kJ

Question 122: Palette 122/130

JEE Mains 2003 MCQ

The internal energy change when a system goes from state A to B is 40 kJ/mole. If the system goes from A to B by a reversible path and returns to state A by an irreversible path what would be the net change in internal energy?

A

> 40 kJ

B

< 40 kJ

C

Zero

D

40 kJ

Question 123: Palette 123/130

JEE Mains 2003 MCQ

If at 298 K the bond energies of C - H, C - C, C = C and H - H bonds are respectively 414, 347, 615 and 435 kJ/mol, the value of enthalpy change for the reaction
H₂C = CH₂(g) + H₂(g) $\to$ H₃C - CH₃(g) at 298 K will be :

A

- 250 kJ

B

+ 125 kJ

C

- 125 kJ

D

+ 250 kJ

Question 124: Palette 124/130

JEE Mains 2003 MCQ

The correct relationship between free energy change in a reaction and the corresponding equilibrium constant K_c is :

A

- $\Delta G$ = RT ln K_c

B

$\Delta G^o$ = RT ln K_c

C

- $\Delta G^o$ = RT ln K_c

D

$\Delta G$ = RT ln K_c

Question 125: Palette 125/130

JEE Mains 2003 MCQ

In an irreversible process taking place at constant T and P and in which only pressure-volume work is being done, the change in Gibbs free energy (dG) and change in entropy (dS), satisfy the criteria :

A

(dS)_{V, E} > 0, (dG)_{T, P} < 0

B

(dS)_{V, E} = 0, (dG)_{T, P} = 0

C

(dS)_{V, E} = 0, (dG)_{T, P} > 0

D

(dS)_{V, E} < 0, (dG)_{T, P} < 0

Question 126: Palette 126/130

JEE Mains 2003 MCQ

The enthalpy change for a reaction does not depend upon :

A

use of different reactants for the same product

B

the nature of intermediate reaction steps

C

the differences in initial or final temperature of involved substances

D

the physical states of reactants and products

Question 127: Palette 127/130

JEE Mains 2002 MCQ

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

A

$\Delta H$ is -ve, $\Delta S$ is +ve

B

$\Delta H$ and $\Delta S$ are both +ve

C

$\Delta H$ and $\Delta S$ are both -ve

D

$\Delta H$ is +ve, $\Delta S$ is -ve

Question 128: Palette 128/130

JEE Mains 2002 MCQ

The heat required to raise the temperature of body by 1 K is called :

A

specific heat

B

thermal capacity

C

water equivalent

D

none of these

Question 129: Palette 129/130

JEE Mains 2002 MCQ

A heat engine absorbs heat Q₁ at temperature T₁ and heat Q₂ at temperature T₂. Work done by the engine is J (Q₁ + Q₂). This data :

A

violates 1^st law of thermodynamics

B

violates 1^st law of thermodynamics if Q₁ is +ve

C

violates 1^st law of thermodynamics if Q₁ is -ve

D

does not violates 1^st law of thermodynamics

Question 130: Palette 130/130

JEE Mains 2002 MCQ

For the reactions
2C + O₂ $\to$ 2CO₂; $\Delta H$ = -393 J
2Zn + O₂ $\to$ 2ZnO; $\Delta H$ = -412 J

A

carbon can oxidise Zn

B

oxidation of carbon is not feasible

C

oxidation of Zn is not feasible

D

Zn can oxidise carbon