The reaction quotient $(\mathrm{Q})$ for the reaction: $\mathrm{N}_{2(g)}+3 \mathrm{H}_{2(g)}…

The reaction quotient $(\mathrm{Q})$ for the reaction:
$\mathrm{N}_{2(g)}+3 \mathrm{H}_{2(g)} \rightleftharpoons 2 \mathrm{NH}_{3(\mathrm{~g})}$
is given by $\mathrm{Q}=\frac{\left[\mathrm{NH}_3\right]^2}{\left[\mathrm{~N}_2\right]\left[\mathrm{H}_2\right]^3}$ The reaction will proceed from right to left if:
  1. $\mathrm{Q}=\mathrm{K}_e$
  2. $\mathrm{Q} < \mathrm{K}_c$
  3. $\mathrm{Q} > \mathrm{K}_c$
  4. $Q=0$

Solution

$\mathrm{N}_{2(g)}+3 \mathrm{H}_{2(g)} \rightleftharpoons 2 \mathrm{NH}_{3(g)}$
$\begin{aligned}
& \mathrm{K}_{\mathrm{C}}=\frac{\left[\mathrm{NH}_3\right]^2}{\left[\mathrm{~N}_2\right]\left[\mathrm{H}_2\right]^3}: \\
& \Delta n=2-4=-2
\end{aligned}$
Thus, the reaction moves in forward direction, when $\mathrm{Q} > \mathrm{K}_c$.

Asked in: NEET 2003

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