Chemical Equilibrium | JEE Main Chemistry Chapter Wise Question Papers

Q 1 :

The following reaction occurs in the Blast furnance where iron ore is reduced to iron metal

${Fe}_{2} O_{3} (s) + 3 CO (g) ⇌ {Fe}_{(l)} + 3 {CO}_{2} (g)$

Using the Le-chatelier's principle, predict which one of the following will not disturb the equilibrium. [2024]

Removal of $CO$
Addition of ${Fe}_{2} O_{3}$
Removal of ${CO}_{2}$
Addition of ${CO}_{2}$

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(2)

${Fe}_{2} O_{3} (s) + 3 CO (g) ⇌ Fe (l) + 3 {CO}_{2} (g)$

$K_{c} = \frac{{[{CO}_{2}]}^{3}}{{[CO]}^{3}}$

$F e_{2} O_{3} (s)$ do not affect the equilibrium. Hence addition or removal of $F e_{2} O_{3} (s)$ or $F e (l)$ do not affect the equilibrium.

Q 2 :

For a certain thermochemical reaction $M \to N$ at $T = 400 K$ , ${ΔH}^{⊝} = 77.2 kJ$ ${mol}^{- 1}, ΔS = 122 {JK}^{- 1}$ , log equilibrium constant (logk) is - ______ $\times 10^{- 1} .$ [2024]

(37)

$Δ G ° = Δ H ° - T Δ S °$

$Δ G ° = 77.2 kJ {mol}^{- 1} - 400 K \times 122 {JK}^{- 1}$

$= 77.2 \times 1000 {Jmol}^{- 1} - 400 K \times 122 {JK}^{- 1}$

$= 28400 J {mol}^{- 1}$

$- 2.303 RT \log_{10} K = ΔG °$

$- 2.303 RT \log_{10} K_{eq} = 28400 J {mol}^{- 1}$

$- 2.303 \times 8.314 J {mol}^{- 1} K^{- 1} \times 400 K \times \log_{10} K_{eq} = 28400 J {mol}^{- 1}$

$\log_{10} K_{e q} = - 3.7 = - 37 \times 10^{- 1}$

Q 3 :

For a certain reaction at 300K, K = 10, then $∆ G^{o}$ for the same reaction is _________ $\times 10^{- 1}$ kJ ${mol}^{- 1}$ . (Given R = 8.314 ${JK}^{- 1}$ ${mol}^{- 1}$ ) [2024]

(57)

$ΔG ° = - 2.303 RT \log_{10} K$

$=-2.303×8.314 J {mol}^{- 1} K^{- 1} \times 300 K \log_{10} 10$

$= - 5744.143 J {mol}^{- 1}$

$= - 5.744 kJ {mol}^{- 1} \approx - 57 \times 10^{- 1} kJ {mol}^{- 1}$

Q 4 :

Consider the equilibrium

$CO(g) + 3 H_{2} (g) ⇌ {CH}_{4} (g) + H_{2} O(g)$

If the pressure applied over the system increases by two fold at constant temperature then

(A) Concentration of reactants and products increases.
(B) Equilibrium will shift in forward directions.
(C) Equilibrium constant increases since concentration of products increase.
(D) Equilibrium constant remains unchanged as concentration of reactants and products remain same.

Choose the correct answer from the options given below: [2025]

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

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(1)

(A) Since pressure is increased, this means volume has been reduced. If volume is reduced, then concentration of each species (reactants as well as products) in the vessel increases.

(B) On increasing the pressure, system moves in a direction with less number of gaseous moles (Le Chatelier’s principle) which is forward direction in given case.

(C) (D) Equilibrium constant does not change upon changing concentration or pressure of reactants or products.

Q 5 :

Given below are two statements:

Statement I: A catalyst cannot alter the equilibrium constant $(K_{c})$ of the reaction, temperature remaining constant.

Statement II: A homogenous catalyst can change the equilibrium composition of a system, temperature remaining constant.

In the light of the above statements, choose the correct answer from the options given below. [2025]

Statement I is false but Statement II is true
Both Statement I and Statement II are true
Both Statement I and Statement II are false
Statement I is true but Statement II is false

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(4)

A catalyst does not affect the position of equilibrium. It does not affect equilibrium constant or composition of reaction mixture.

Q 6 :

In the following system,

${PCl}_{5} (g) ⇌ {PCl}_{3} (g) + {Cl}_{2} (g)$ at equilibrium, upon addition of xenon gas at constant T and P, the concentration of [2025]

${PCl}_{5}$ will increase
${Cl}_{2}$ will decrease
${PCl}_{5}, {PCl}_{3}$ and ${Cl}_{2}$ remain constant
${PCl}_{3}$ will increase

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(4)

If inert gas is added at constant pressure, then volume of the system increases. This decreases partial pressure of components of the system. To increase the partial pressure, system moves in a direction of more number of gaseous moles i.e. in forward direction.

Q 7 :

The effect of addition of helium gas to the following reaction in equilibrium state, is: ${PCl}_{5} (g) ⇌ {PCl}_{3} (g) + {Cl}_{2} (g)$ [2023]

Addition of helium will not affect the equilibrium.
The equilibrium will shift in the forward direction and more of ${Cl}_{2}$ and ${PCl}_{3}$ gases will be produced.
The equilibrium will go backward due to suppression of dissociation of ${PCl}_{5}$ .
Helium will deactivate ${PCl}_{5}$ and reaction will stop.

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(2)

At constant pressure equilibrium shift where number of moles of gas increases so this reaction goes forward direction.

Q 8 :

Water decomposes at 2300 K

$H_{2} O (g) ⇌ H_{2} (g) + \frac{1}{2} O_{2} (g)$

The percent of water decomposing at 2300 K and 1 bar is __________ (Nearest integer).

Equilibrium constant for the reaction is $2 \times 10^{- 3}$ at 2300 K. [2023]

(2)

$\begin{matrix} H_{2} O (g) & ⇌ & H_{2} (g) & + & \frac{1}{2} O_{2} (g) \\ 1 - α & α & α / 2 \end{matrix}$

$K_{p} = \frac{α {(\frac{α}{2})}^{1 / 2}}{1 - α} = 2 \times 10^{- 3}$

$= \frac{{(α)}^{3 / 2}}{\sqrt{2} (1 - α)} = 2 \times 10^{- 3}$

$= {(α)}^{3 / 2} = 2 \sqrt{2} \times 10^{- 3} (α ≪ 1)$

${(α)}^{3 / 2} = \sqrt{8} \times 10^{- 3}$

$α = 2 \times 10^{- 2}$

$% α = 2 \times 10^{- 2} \times 100 = 2$

Q 9 :

At 298 K

$N_{2} (g) + 3 H_{2} (g) ⇌ 2 {NH}_{3} (g), K_{1} = 4 \times 10^{5}$

$N_{2} (g) + O_{2} (g) ⇌ 2 NO (g), K_{2} = 1.6 \times 10^{12}$

$H_{2} (g) + \frac{1}{2} O_{2} (g) ⇌ H_{2} O (g), K_{3} = 1.0 \times 10^{- 13}$

Based on above equilibria, the equilibrium constant of the reaction, $2 {NH}_{3} (g) + \frac{5}{2} O_{2} (g) ⇌ 2 NO (g) + 3 H_{2} O (g)$ is ________ $\times 10^{- 33}$ (Nearest integer). [2023]

(4)

$Target equation = eq(2) - eq(1) + 3 eq(3)$

$K = \frac{K_{2} \times {(K_{3})}^{3}}{K_{1}} = \frac{1.6 \times 10^{12} \times {(1 \times 10^{- 13})}^{3}}{4 \times 10^{5}}$

$= \frac{16 \times 10^{11} \times 10^{- 39}}{4 \times 10^{5}} = 4 \times 10^{- 33} = 4$

Q 10 :

Consider the following equation:

$2 {SO}_{2} (g) + O_{2} (g) ⇌ 2 {SO}_{3} (g), Δ H = - 190 kJ$

The number of factors which will increase the yield of ${SO}_{3}$ at equilibrium from the following is _______ .

A. Increasing temperature

B. Increasing pressure

C. Adding more ${SO}_{2}$

D. Adding more $O_{2}$

E. Addition of catalyst [2023]

(3)

(i) As reaction is exothermic so on increase in temperature equilibrium shift in backward direction.

(ii) On increasing pressure equilibrium shift in forward direction.

(iii) Addition of catalyst does not affect equilibrium it only increases rate of reaction.

Q 11 :

For reaction: ${SO}_{2} (g) + \frac{1}{2} O_{2} (g) ⇌ {SO}_{3} (g)$

$K_{p} = 2 \times 10^{12}$ at $27 ° C$ and 1 atm pressure. The $K_{C}$ for the same reaction is _______ $\times 10^{13}$ . (Nearest integer)

$(Given R = {0.082 L atm K}^{- 1} {mol}^{- 1})$ [2023]

(1)

$k_{p} = k_{c} {(R T)}^{Δ n}$

$k_{c} = \frac{k_{p}}{{(R T)}^{Δ n}} = \frac{2 \times 10^{12}}{{(0.082 \times 300)}^{- 1 / 2}} = 2 \times 10^{12} \times 4.95 = 0.99 \times 10^{13}$

$\approx 1 \times 10^{13}$

Q 12 :

The value of log K for the reaction $A ⇌ B$ at 298 K is _______. (Nearest integer)

$Given: Δ H ° = - {54.07 kJ mol}^{- 1}$

$Δ S ° = {10 J K}^{- 1} {mol}^{- 1}$

$(Take 2.303×8.314×298=5705)$ [2023]

(10)

$Δ G ° = Δ H ° - T Δ S °$

$Δ G ° = - 54070 - 298 \times 10 = - 57050 J$

$Δ G ° = - {2.303 RT log K}_{e q}$

$- 57050 J = - {5705 log K}_{e q}$

${log K}_{e q} = 10$

Q 13 :

For the reaction $N_{2} O_{4} ⇌ 2 {NO}_{2}$ graph is plotted as shown below. Identify correct statements:

A. Standard free energy change for the reaction is $- 5.40 kJ mol⁻¹ .$

B. As ${ΔG}^{⊝}$ in graph is positive, $N_{2} O_{4}$ will not dissociate into ${NO}_{2}$ at all.

C. Reverse reaction will go to completion.
D. When 1 mole of $N_{2} O_{4}$ changes into equilibrium mixture, value of ${ΔG}^{⊝} = - 0.84 kJ mol⁻¹.$
E. When 2 mole of ${NO}_{2}$ changes into equilibrium mixture, ${ΔG}^{⊝}$ for equilibrium mixture is $- 6.24 kJ mol⁻¹.$

Choose the correct answer from the options given below : [2026]

B and C only
D and E only
A and D only
C and E only

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(2)

$(A) Δ_{r} G ° = G_{B} ° - G_{A} ° = + v e$

$(B) Δ_{r} G ° = + v e, N_{2} O_{4} will partially dissociate into N O_{2} .$

$(C) For reverse reaction$

$It is partially completed as there is equilibrium at E.$

$(D) For 1 mole N_{2} O_{4}; Δ_{r} G ° = - 0.84 {kJ mol}^{- 1}$

$(E) For 2 mole N O_{2}; Δ_{r} G ° = - 5.4 - 0.84$

$= - 6.24 {kJ mol}^{- 1}$

Q 14 :

Dissociation of a gas $A_{2}$ takes place according to the following chemical reaction. At equilibrium, the total pressure is 1 bar at 300K.

$A_{2} (g) ⇌ 2 A (g)$

The standard Gibbs energy of formation of the involved substances has been provided below:

Substance $Δ G_{f} ° / {kJ mol}^{- 1}$

$A_{2}$ - 100.00

$A$ - 50.832

The degree of dissociation of $A_{2} (g)$ is given by ${(x \times 10^{- 2})}^{1 / 2}$ where $x$ =_______. (Nearest integer).

[Given: $R = 8 {J mol}^{- 1} K^{- 1}, \log 2 = 0.3010, \log 3 = 0.48$ ]

Assume degree of dissociation is not negligible. [2026]

(33)

$- 1.664 \times 10^{3} = - 8.3 \times 300 \ln K_{p}$

$\ln K_{p} = 0.693$

$K_{p} = 2$

$2 = \frac{4 α^{2} P_{0}}{1 - α^{2}}$

$α = \frac{1}{\sqrt{3}}$

$α = {(\frac{100}{3} \times 10^{- 2})}^{1 / 2}$

$= {(33.33 \times 10^{- 2})}^{1 / 2}$

Q 15 :

Observe the following equilibrium in a 1 L flask.

$A (g) ⇌ B (g)$

At T(K), the equilibrium concentrations of A and B are 0.5 M and 0.375 M respectively. 0.1 moles of A is added into the flask and heated to T(K) to establish the equilibrium again. The new equilibrium concentrations (in M) of A and B are respectively [2026]

0.742, 0.557
0.557, 0.418
0.367, 0.275
0.53, 0.4

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(2)

$\begin{matrix} A & ⇌ & B \\ 0.5 M & 0.375 M & (At equilibrium) \end{matrix}$

$K_{e q} = \frac{{[B]}_{e q}}{{[A]}_{e q}} = \frac{0.375}{0.5} = 0.75$

$Now 0.1 mole of A is added so reaction will move in forward direction.$

$\begin{matrix} A & ⇌ & B \\ 0.6 - x & 0.375 + x \end{matrix}$

$K_{e q} = 0.75 = \frac{0.375 + x}{0.6 - x}$

$0.45 - 0.75 x = 0.375 + x$

$1.75 x = 0.075$

$x = \frac{0.075}{1.75} = \frac{3}{70} = 0.043$

$Moles of A = 0.6 - 0.043 = 0.557$

$Moles of B = 0.375 + 0.043 = 0.418$

$Ans. (2) is correct.$

Q 16 :

$X_{2} (g) + Y_{2} (g) ⇌ 2 Z (g)$

$X_{2} (g)$ and $Y_{2} (g)$ are added to a 1 L flask and it is found that the system attains the above equilibrium at T(K) with the number of moles of $X_{2} (g), Y_{2} (g) and Z (g)$ being 3, 3 and 9 mol respectively (equilibrium moles). Under this condition of equilibrium, 10 mol of Z(g) is added to the flask and the temperature is maintained at T(K). Then, the number of moles of Z(g) in the flask when the new equilibrium is established is ______. (Nearest integer) [2026]

(15)

$X_{2} (g) + Y_{2} (g) ⇌ 2 Z (g)$

$K_{c} = \frac{{(9)}^{2}}{3 \times 3} = 9$

Now 10 moles of Z are added then reaction will move in backward direction.

$X_{2} (g) + Y_{2} (g) ⇌ 2 Z (g)$

$\begin{matrix} 3 + X & 3 + X & 19 - 2 X \end{matrix}$

$K_{c} = \frac{{(19 - 2 X)}^{2}}{(3 + X) (3 + X)} = 9$

$\frac{19 - 2 X}{3 + X} = 3$

$19 - 2 X = 9 + 3 X$

$10 = 5 X$

$X = 2$

$At equilibrium \Rightarrow moles of Z = 19 - 2 \times 2 = 15 moles$

Topic Question Set

Q 1 :

The following reaction occurs in the Blast furnance where iron ore is reduced to iron metal

${Fe}_{2} O_{3} (s) + 3 CO (g) ⇌ {Fe}_{(l)} + 3 {CO}_{2} (g)$

Using the Le-chatelier's principle, predict which one of the following will not disturb the equilibrium. [2024]

Q 2 :

For a certain thermochemical reaction $M \to N$ at $T = 400 K$ , ${ΔH}^{⊝} = 77.2 kJ$ ${mol}^{- 1}, ΔS = 122 {JK}^{- 1}$ , log equilibrium constant (logk) is - ______ $\times 10^{- 1} .$ [2024]

Q 3 :

For a certain reaction at 300K, K = 10, then $∆ G^{o}$ for the same reaction is _________ $\times 10^{- 1}$ kJ ${mol}^{- 1}$ . (Given R = 8.314 ${JK}^{- 1}$ ${mol}^{- 1}$ ) [2024]

Q 6 :

In the following system,

${PCl}_{5} (g) ⇌ {PCl}_{3} (g) + {Cl}_{2} (g)$ at equilibrium, upon addition of xenon gas at constant T and P, the concentration of [2025]

Q 7 :

The effect of addition of helium gas to the following reaction in equilibrium state, is: ${PCl}_{5} (g) ⇌ {PCl}_{3} (g) + {Cl}_{2} (g)$ [2023]

Q 8 :

Water decomposes at 2300 K

$H_{2} O (g) ⇌ H_{2} (g) + \frac{1}{2} O_{2} (g)$

The percent of water decomposing at 2300 K and 1 bar is __________ (Nearest integer).

Equilibrium constant for the reaction is $2 \times 10^{- 3}$ at 2300 K. [2023]

Q 11 :

For reaction: ${SO}_{2} (g) + \frac{1}{2} O_{2} (g) ⇌ {SO}_{3} (g)$

$K_{p} = 2 \times 10^{12}$ at $27 ° C$ and 1 atm pressure. The $K_{C}$ for the same reaction is _______ $\times 10^{13}$ . (Nearest integer)

$(Given R = {0.082 L atm K}^{- 1} {mol}^{- 1})$ [2023]

Q 12 :

The value of log K for the reaction $A ⇌ B$ at 298 K is _______. (Nearest integer)

$Given: Δ H ° = - {54.07 kJ mol}^{- 1}$

$Δ S ° = {10 J K}^{- 1} {mol}^{- 1}$

$(Take 2.303×8.314×298=5705)$ [2023]

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Substance	$Δ G_{f} ° / {kJ mol}^{- 1}$
$A_{2}$	- 100.00
$A$	- 50.832

Topic Question Set

Q 1 : The following reaction occurs in the Blast furnance where iron ore is reduced to iron metal Fe2O3(s)+3CO(g)⇌Fe(l)+3CO2(g) Using the Le-chatelier's principle, predict which one of the following will not disturb the equilibrium. [2024]

Q 2 : For a certain thermochemical reaction M→N at T=400K, ΔH⊝=77.2kJ mol-1,ΔS=122JK-1, log equilibrium constant (logk) is - ______ ×10-1. [2024]

Q 3 : For a certain reaction at 300K, K = 10, then ∆Go for the same reaction is _________ ×10-1 kJ mol-1. (Given R = 8.314 JK-1 mol-1) [2024]

Q 6 : In the following system, PCl5(g)⇌PCl3(g)+Cl2(g) at equilibrium, upon addition of xenon gas at constant T and P, the concentration of [2025]

Q 7 : The effect of addition of helium gas to the following reaction in equilibrium state, is: PCl5(g)⇌PCl3(g)+Cl2(g) [2023]

Q 8 : Water decomposes at 2300 K H2O(g)⇌H2(g)+12O2(g) The percent of water decomposing at 2300 K and 1 bar is __________ (Nearest integer). Equilibrium constant for the reaction is 2×10-3 at 2300 K. [2023]

Q 9 : At 298 K N2(g)+3H2(g)⇌2NH3(g), K1=4×105 N2(g)+O2(g)⇌2NO(g), K2=1.6×1012 H2(g)+12O2(g)⇌H2O(g), K3=1.0×10-13 Based on above equilibria, the equilibrium constant of the reaction, 2NH3(g)+52O2(g)⇌2NO(g)+3H2O(g) is ________ ×10-33 (Nearest integer). [2023]

Q 10 : Consider the following equation: 2SO2(g)+O2(g)⇌2SO3(g), ΔH=-190 kJ The number of factors which will increase the yield of SO3 at equilibrium from the following is _______ . A. Increasing temperature B. Increasing pressure C. Adding more SO2 D. Adding more O2 E. Addition of catalyst [2023]

Q 11 : For reaction: SO2(g)+12O2(g)⇌SO3(g) Kp=2×1012 at 27°C and 1 atm pressure. The KC for the same reaction is _______ ×1013. (Nearest integer) (Given R=0.082 L atm K-1 mol-1) [2023]

Q 12 : The value of log K for the reaction A⇌B at 298 K is _______. (Nearest integer) Given: ΔH°=-54.07 kJ mol-1 ΔS°=10 J K-1 mol-1 (Take 2.303×8.314×298=5705) [2023]

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Q 1 :

The following reaction occurs in the Blast furnance where iron ore is reduced to iron metal

${Fe}_{2} O_{3} (s) + 3 CO (g) ⇌ {Fe}_{(l)} + 3 {CO}_{2} (g)$

Using the Le-chatelier's principle, predict which one of the following will not disturb the equilibrium. [2024]

Q 2 :

For a certain thermochemical reaction $M \to N$ at $T = 400 K$ , ${ΔH}^{⊝} = 77.2 kJ$ ${mol}^{- 1}, ΔS = 122 {JK}^{- 1}$ , log equilibrium constant (logk) is - ______ $\times 10^{- 1} .$ [2024]

Q 3 :

For a certain reaction at 300K, K = 10, then $∆ G^{o}$ for the same reaction is _________ $\times 10^{- 1}$ kJ ${mol}^{- 1}$ . (Given R = 8.314 ${JK}^{- 1}$ ${mol}^{- 1}$ ) [2024]

Q 6 :

In the following system,

${PCl}_{5} (g) ⇌ {PCl}_{3} (g) + {Cl}_{2} (g)$ at equilibrium, upon addition of xenon gas at constant T and P, the concentration of [2025]

Q 7 :

The effect of addition of helium gas to the following reaction in equilibrium state, is: ${PCl}_{5} (g) ⇌ {PCl}_{3} (g) + {Cl}_{2} (g)$ [2023]

Q 8 :

Water decomposes at 2300 K

$H_{2} O (g) ⇌ H_{2} (g) + \frac{1}{2} O_{2} (g)$

The percent of water decomposing at 2300 K and 1 bar is __________ (Nearest integer).

Equilibrium constant for the reaction is $2 \times 10^{- 3}$ at 2300 K. [2023]

Q 11 :

For reaction: ${SO}_{2} (g) + \frac{1}{2} O_{2} (g) ⇌ {SO}_{3} (g)$

$K_{p} = 2 \times 10^{12}$ at $27 ° C$ and 1 atm pressure. The $K_{C}$ for the same reaction is _______ $\times 10^{13}$ . (Nearest integer)

$(Given R = {0.082 L atm K}^{- 1} {mol}^{- 1})$ [2023]

Q 12 :

The value of log K for the reaction $A ⇌ B$ at 298 K is _______. (Nearest integer)

$Given: Δ H ° = - {54.07 kJ mol}^{- 1}$

$Δ S ° = {10 J K}^{- 1} {mol}^{- 1}$

$(Take 2.303×8.314×298=5705)$ [2023]