Answer
$\text { (c) } \mathrm{N}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}$
Work Step by Step
According to Le Chatelier’s principle, a change in pressure affects equilibrium only if the number of moles of gas changes during the reaction.
If the total number of gas molecules (moles) on the reactant side = total number on the product side, then equilibrium is not affected by pressure.
The reaction $\text { (c) } \mathrm{N}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}$ is the one whose equilibrium composition is not affected by pressure, because the number of gas molecules is the same on both sides.
The corect answer is (c).
