Question

$N_2+3H_2$ $\to 2N{H}_3$
Which is the correct statement if $N_2$ is added to equilibrium condition?

• A. The equilibrium will shift to forward direction because according to $I{I}^{nd}$ law thermodynamics the entropy must increase in the direction of the spontaneous reaction.
• B. The condition for equilibrium is $G_{N_2}+3G_{H_2}=2G_{N{H}_3}$ 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 the catalyst, which increases the rate both the forward and backward reactions to the same extent.
• 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.

Answer 1

Answer: (B)

The condition for equilibrium is $G_{N_2}+3G_{H_2}=2G_{N{H}_3}$ 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 the catalyst, which increases the rate both the forward and backward reactions to the same extent.

$N_2+3H_{2^{}}\rightleftharpoons 2N{H}_3$
The statement B is correct statement if $N_2$ is added at equilibrium condition.
(A) The equilibrium will shift to forward direction because according to Le Châtelier's principle. When a reactant is added, more of it will be consumed during the reaction to form product so as to nullify the effect of added reactant.

(b) The condition for equilibrium is $G_{N_2}+3G_{H_2}=2G_{N{H}_3}$ where $G$ is Gibbs free energy per mole of the gaseous species measured at that partial pressure. In other words, the Gibbs free energy change during equilibrium reaction is zero. 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.

(C) The catalyst will increase the rate of forward reaction and that of backward reaction by equal extents.

(D) Catalyst will alter the rate of forward as well as backward reaction.