Core Syllabus Module

Chemical Equilibrium

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Law of Mass Action

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Le-Chatelier's Principle

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Chapter Elite-20 Challenge Zone

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JEE Main 2021

LEVELJEE Advanced

The gas phase reaction $2 A (g) ⇌ A_{2} (g)$ at $400 K$ has $Δ G^{\circ} = + 25.2 kJ mol^{- 1}$ . The equilibrium constant $K_{C}$ for this reaction is ......... $\times 1 0^{- 2}$ . (Round off to the nearest integer). [Use : $R = 8.3 J mol^{- 1} K^{- 1}$ , $ln 10 = 2.3$ ] $lo g_{10} 2 = 0.30$ , $1 atm = 1 bar$ ] $[antilog (- 0.3) = 0.501]$

JEE Advanced 2016

LEVELJEE Advanced

Comprehension Passage

Thermal decomposition of gaseous

X_{2}

to gaseous X at 298 K takes place according to the following equation :

X_{2} (g) ⇌ 2 X (g)

The standard reaction Gibbs energy,

Δ_{r} G^{\circ}

, of this reaction is positive. At the start of the reaction, there is one mole of

X_{2}

and no X. As the reaction proceeds, the number of moles of X formed is given by

β

. Thus,

β_{equilibrium}

is the number of moles of X formed at equilibrium. The reaction is carried out at a constant total pressure of 2 bar. Consider the gases to behave ideally. (Given :

R = 0.083 L bar K^{- 1} mol^{- 1}

)

Question 1:

The equilibrium constant $K_{P}$ for this reaction at 298 K, in terms of $β_{equilibrium}$ , is

(A)

\frac{8 β _{equilibrium}^{2}}{2 - β _{equilibrium}}

(B)

\frac{8 β _{equilibrium}^{2}}{4 - β _{equilibrium}^{2}}

(C)

\frac{4 β _{equilibrium}^{2}}{2 - β _{equilibrium}}

(D)

\frac{4 β _{equilibrium}^{2}}{4 - β _{equilibrium}^{2}}

Question 2:

The INCORRECT statement among the following , for this reaction, is

(A)

Decrease in the total pressure will result in formation of more moles of gaseous X

(B)

At the start of the reaction, dissociation of gaseous

X_{2}

takes place spontaneously

(C)

β_{equilibrium} = 0.7

(D)

K_{C} < 1

JEE Advanced 2015

LEVELJEE Advanced

The % yield of ammonia as a function of time in the reaction $N_{2} (g) + 3 H_{2} (g) ⇌ 2 N H_{3} (g), Δ H < 0$ at $(P, T_{1})$ is given below - If this reaction is conducted at $(P, T_{2})$ , with $T_{2} > T_{1}$ , the % yield of ammonia as a function of time is represented by -

5.1 g $NH_{4} SH$ is introduced in 3.0 L evacuated flask at $32 7^{\circ} C$ . 30\% of the solid $NH_{4} SH$ decomposed to $NH_{3}$ and $H_{2} S$ as gases. The $K_{p}$ of the reaction at $32 7^{\circ} C$ is ( $R = 0.082 atm mol^{- 1} K^{- 1}$ , molar mass of $S = 32 g mol^{- 1}$ , molar mass of $N = 14 g mol^{- 1}$ )

(A)

0.242 \times 1 0^{- 4} atm^{2}

(B)

0.242 atm^{2}

(C)

4.9 \times 1 0^{- 3} atm^{2}

(D)

1 \times 1 0^{- 4} atm^{2}

JEE Main 2019

LEVELJEE Advanced

Two solids dissociate as follows: $A (s) ⇌ B (g) + C (g); K_{p_{1}} = x atm^{2}$ $D (s) ⇌ C (g) + E (g); K_{p_{2}} = y atm^{2}$ The total pressure when both the solids dissociate simultaneously is

(A)

x + y atm

(B)

x^{2} + y^{2} atm

(C)

(x + y) atm

(D)

2 (x + y) atm

JEE Main 2021

LEVELJEE Advanced

A homogeneous ideal gaseous reaction, $A B_{2} (g) ⇌ A (g) + 2 B (g)$ is carried out in a 25 L flask at 27°C. The initial amount of $A B_{2}$ was 1 mole and the equilibrium pressure was 1.9 atm. The value of $K_{p}$ is $x \times 1 0^{- 2}$ . The value of $x$ is ………… .

LEVELJEE Advanced

The equilibrium constants $K_{p_{1}}$ and $K_{p_{2}}$ for the reactions $X ⇌ 2 Y$ and $Z ⇌ P + Q$ , respectively are in the ratio of $1 : 9$ . If the degree of dissociation of $X$ and $Z$ be equal, then the ratio of total pressure at these equilibria is

(A)

1 : 36

(B)

1 : 1

(C)

1 : 3

(D)

1 : 9

JEE Main 2019

LEVELJEE Advanced

Consider the reaction, $N_{2} (g) + 3 H_{2} (g) ⇌ 2 N H_{3} (g)$ The equilibrium constant of the above reaction is $K_{p}$ . If pure ammonia is left to dissociate, the partial pressure of ammonia at equilibrium is given by (Assume that $p_{N H_{3}} ≪ p_{total}$ at equilibrium)

(A)

\frac{3 ^{3/2} K _{p}^{1/2} p ^{2}}{4}

(B)

\frac{3 ^{3/2} K _{p}^{1/2} p ^{2}}{16}

(C)

\frac{K _{p}^{1/2} p ^{2}}{16}

(D)

\frac{K _{p}^{1/2} p ^{2}}{4}

JEE Main 2015

LEVELJEE Advanced

The standard Gibbs energy change at $300 K$ for the reaction, $2 A ⇌ B + C$ is $2494.2 J$ . At a given time, the composition of the reaction mixture is $[A] = \frac{1}{2}, [B] = 2$ and $[C] = \frac{1}{2}$ . The reaction proceeds in the $[R = 8.314 J K^{- 1} mol^{- 1}, e = 2.718]$

(A)

forward direction because

Q < K_{c}

(B)

reverse direction because

Q > K_{c}

(C)

forward direction because

Q > K_{c}

(D)

reverse direction because

Q < K_{c}

JEE Main 2021

LEVELJEE Advanced

When $5.1 g$ of solid $NH_{4} HS$ is introduced into a two litre evacuated flask at $2 7^{\circ} C$ , $20%$ of the solid decomposes into gaseous ammonia and hydrogen sulphide. The $K_{p}$ for the reaction at $2 7^{\circ} C$ is $x \times 1 0^{- 2}$ . The value of $x$ is ........... . [Given, $R = 0.082 L atm K^{- 1} mol^{- 1}$ ]

JEE Main 2021

LEVELJEE Main

For the reaction, $A (g) ⇌ B (g)$ at $495 K$ , $Δ_{r} G^{\circ} = - 9.478 kJ mol^{- 1}$ . If we start the reaction in a closed container at $495 K$ with $22$ millimoles of $A$ , the amount of $B$ in the equilibrium mixture is ......... millimoles (Round off to the nearest integer). $[R = 8.314 J mol^{- 1} K^{- 1}, ln 10 = 2.303]$

JEE Main 2018

LEVELJEE Main

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

$PCl_{5} ⇌ PCl_{3} + Cl_{2}, K_{c} = 1.844$ $3.0$ moles of $PCl_{5}$ is introduced in a $1 L$ closed reaction vessel at $380 K$ . The number of moles of $PCl_{5}$ at equilibrium is ............ $\times 1 0^{- 3}$ . (Round off to the nearest integer)

LEVELJEE Main

An amount of solid $NH_{4} HS$ is placed in a flask already containing ammonia gas at a certain temperature and $0.50 atm$ pressure. Ammonium hydrogen sulphide decomposes to yield $NH_{3}$ and $H_{2} S$ gases in the flask. When the decomposition reaction reaches equilibrium, the total pressure in the flask rises to $0.84 atm$ . The equilibrium constant for the decomposition of $NH_{4} HS$ at this temperature is

(A)

0.11

(B)

0.17

(C)

0.18

(D)

0.30

JEE Main 2019

LEVELJEE Main

In a chemical reaction, $A + 2 B ⇌ 2 C + D$ , the initial concentration of $B$ was 1.5 times of the concentration of $A$ , but the equilibrium concentrations of $A$ and $B$ were found to be equal. The equilibrium constant ( $K$ ) for the aforesaid chemical reaction is

(A)

\frac{1}{4}

The number of moles of $NH_{3}$ , that must be added to $2 L$ of $0.80 M$ $AgNO_{3}$ in order to reduce the concentration of $Ag^{+}$ ions to $5.0 \times 1 0^{- 8} M$ ( $K_{formation}$ for $[Ag (NH_{3})_{2}]^{+} = 1.0 \times 1 0^{8}$ ) is ......... (Nearest integer) [Assume no volume change on adding $NH_{3}$ ]

JEE Main 2019

LEVELJEE Main

For the reaction, $2 SO_{2} (g) + O_{2} (g) ⟶ 2 SO_{3} (g)$ , $Δ H = - 57.2 kJ mol^{- 1}$ and $K_{c} = 1.7 \times 1 0^{16}$ . Which of the following statement is incorrect?

(A)

The equilibrium constant decreases as the temperature increases

(B)

The addition of inert gas at constant volume will not affect the equilibrium constant

(C)

The equilibrium will shift in forward direction as the pressure increases

(D)

The equilibrium constant is large suggestive of reaction going to completion and so no catalyst is required

JEE Main 2019

LEVELJEE Main

For the following reactions, equilibrium constants are given : $S (s) + O_{2} (g) ⇌ SO_{2} (g); K_{1} = 1 0^{52}$ $2 S (s) + 3 O_{2} (g) ⇌ 2 SO_{3} (g); K_{2} = 1 0^{129}$ The equilibrium constant for the reaction, $2 SO_{2} (g) + O_{2} (g) ⇌ 2 SO_{3} (g)$ is

(A)

1 0^{25}

(B)

1 0^{77}

(C)

1 0^{154}

(D)

1 0^{181}

JEE Main 2019

LEVELJEE Main

The values of $\frac{K _{p}}{K _{C}}$ for the following reactions at $300 K$ are, respectively (At $300 K$ , $R T = 24.62 dm^{3} atm mol^{- 1}$ ) $N_{2} (g) + O_{2} (g) ⇌ 2 NO (g)$ $N_{2} O_{4} (g) ⇌ 2 NO_{2} (g)$ $N_{2} (g) + 3 H_{2} (g) ⇌ 2 NH_{3} (g)$

(A)

1

24.62 dm^{3} atm mol^{- 1}

606.0 dm^{6} atm^{2} mol^{- 2}

(B)

1

24.62 dm^{3} atm mol^{- 1}

1.65 \times 1 0^{- 3} dm^{- 6} atm^{- 2} mol^{2}

(C)

24.62 dm^{3} atm mol^{- 1}

606.0 dm^{6} atm^{- 2} mol^{2}

1.65 \times 1 0^{- 3} dm^{- 6} atm^{- 2} mol^{2}

(D)

1

4.1 \times 1 0^{- 2} dm^{- 3} atm^{- 1} mol

606 dm^{6} atm^{2} mol^{- 2}

JEE Main 2020

LEVELJEE Main

Consider the following reaction : $N_{2} O_{4} (g) ⇌ 2 N O_{2} (g); Δ H^{\circ} = + 58 kJ$ For each of the following cases (A, B), the direction in which the equilibrium shifts is (A) temperature is decreased. (B) pressure is increased by adding $N_{2}$ at constant $T$ .

(A)

(A) towards product, (B) towards reactant

(B)

(A) towards reactant, (B) no change

(C)

(A) towards reactant, (B) towards product

(D)

(A) towards product, (B) no change

Micro-Topic Strategy Matrix

Law of Mass Action

Le-Chatelier's Principle

Chapter Elite-20 Challenge Zone

Comprehension Passage

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The equilibrium constant KP​ for this reaction at 298 K, in terms of βequilibrium​ , is

The INCORRECT statement among the following , for this reaction, is

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Two solids dissociate as follows: A(s)⇌B(g)+C(g);Kp1​​=x atm2 D(s)⇌C(g)+E(g);Kp2​​=y atm2 The total pressure when both the solids dissociate simultaneously is

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } Which of the following lines correctly show the temperature dependence of equilibrium constant, K, for an exothermic reaction?

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } For the reaction, 2SO2​(g)+O2​(g)⟶2SO3​(g), ΔH=−57.2 kJ mol−1 and Kc​=1.7×1016. Which of the following statement is incorrect?

The equilibrium constant $K_{P}$ for this reaction at 298 K, in terms of $β_{equilibrium}$ , is

Two solids dissociate as follows: $A (s) ⇌ B (g) + C (g); K_{p_{1}} = x atm^{2}$ $D (s) ⇌ C (g) + E (g); K_{p_{2}} = y atm^{2}$ The total pressure when both the solids dissociate simultaneously is

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

For the reaction, $2 SO_{2} (g) + O_{2} (g) ⟶ 2 SO_{3} (g)$ , $Δ H = - 57.2 kJ mol^{- 1}$ and $K_{c} = 1.7 \times 1 0^{16}$ . Which of the following statement is incorrect?