Chemical and Ionic Equilibrium 1 Question 15
16. $\mathrm{N}{2}+3 \mathrm{H}{2} \rightleftharpoons 2 \mathrm{NH}_{3}$
Which is correct statement if $\mathrm{N}_{2}$ is added at equilibrium condition?
(2006, 3M)
(a) The equilibrium will shift to forward direction because according to Ind law of thermodynamics, the entropy must increases in the direction of spontaneous reaction
(b) The condition for equilibrium is $G\left(\mathrm{~N}{2}\right)+3 G\left(\mathrm{H}{2}\right)$ $=2 G\left(\mathrm{NH}_{3}\right)$ 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
(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
Show Answer
Solution:
- At equilibrium,
$$ \Delta G=0 $$
$$ G(\text { reactants })=G \text { (products) } $$
$$ G\left(\mathrm{~N}{2}\right)+3 G\left(\mathrm{H}{2}\right)=2 G\left(\mathrm{NH}_{3}\right) $$
A catalyst does not affect either equilibrium composition or equilibrium constant, it just increases rate of both forward and backward reaction but by the same factor.
