$N_2 + 3 H_2 \rightleftharpoons 2 NH_3$
Which statement is correct if $N_2$ is added at equilibrium condition?

• A
  The equilibrium will shift to the forward direction because according to the $II^{nd}$ law of thermodynamics,the entropy must increase in the direction of a spontaneous reaction.
• B
  The condition for equilibrium is $G_{N_2} + 3 G_{H_2} = 2 G_{NH_3}$,where $G$ is the Gibbs free energy per mole of the gaseous species measured at that partial pressure. The condition of equilibrium is unaffected by the use of a catalyst,which increases the rate of both the forward and backward reactions to the same extent.
• C
  The catalyst will increase the rate of the forward reaction by $\alpha$ and that of the backward reaction by $\beta$.
• D
  $A$ catalyst will not alter the rate of either reaction.