$\mathrm{N}_{2}+3 \mathrm{H}_{2} \rightleftharpoons 2 \mathrm{NH}_{3}$ Which is correct statement if $\mathrm{N}_{2}$ is added at equilibrium condition?

(B) The condition for equilibrium is $\mathrm{G}_{\mathrm{N}_{2}}+3 \mathrm{G}_{\mathrm{H}_{2}}=2 \mathrm{G}_{\mathrm{NH}_{3}}$ where G is Gibbs free energy per mole of the gaseous species measured at that partial pressure. The condition of equilibrium is unaffected by the use of catalyst, which increases the rate of both the forward and backward reactions to the same extent.

(A) The equilibrium will shift to forward direction because according to II ${ }^{\mathrm{nd}}$ law of thermodynamics the entropy must increases in the direction of spontaneous reaction.

(C) The catalyst will increase the rate of forward reaction by $\alpha$ and that of backward reaction by $\beta$.

(D) Catalyst will not alter the rate of either of the reaction.

JEE Advanced · 2006 · 09 Apr 2006 · Equilibrium

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N_{2} + 3 H_{2} ⇌ 2 NH_{3}

Which is correct statement if

N_{2}

is added at equilibrium condition?

(A)The equilibrium will shift to forward direction because according to II $^{nd}$ law of thermodynamics the entropy must increases in the direction of spontaneous reaction.
(B)The condition for equilibrium is $G_{N_{2}} + 3 G_{H_{2}} = 2 G_{NH_{3}}$ where G is Gibbs free energy per mole of the gaseous species measured at that partial pressure. The condition of equilibrium is unaffected by the use of catalyst, which increases the rate of both the forward and backward reactions to the same extent.✓ Correct
(C)The catalyst will increase the rate of forward reaction by $α$ and that of backward reaction by $β$ .
(D)Catalyst will not alter the rate of either of the reaction.

Answer: (B)

Solution

At equilibrium, the condition

Δ G = 0

gives

\sum ν_{i} G_{i} = 0

, which for this reaction is

G_{N_{2}} + 3 G_{H_{2}} = 2 G_{NH_{3}}

, where G represents the molar Gibbs free energy at the respective partial pressures. A catalyst increases the rates of both forward and backward reactions equally, leaving the equilibrium position unchanged. Option (A) is incorrect because adding

N_{2}

shifts equilibrium forward by Le Chatelier's principle, not due to entropy considerations alone.

JEE Advanced · 2006 · 09 Apr 2006 · Single correct option

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JEE Advanced · 2006 · 09 Apr 2006 · Equilibrium

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