A reaction mixture containing $\mathrm{H}_{2}, \mathrm{~N}_{2}$ and $\mathrm{NH}_{3}$ has partial pressures…

A reaction mixture containing $\mathrm{H}_{2}, \mathrm{~N}_{2}$ and $\mathrm{NH}_{3}$ has partial pressures $2 \mathrm{~atm}, 1 \mathrm{~atm}$ and $3 \mathrm{~atm}$ respectively at $725 \mathrm{~K}$. If the value of $\mathrm{K}_{\mathrm{p}}$ for the reaction, $\mathrm{N}_{2(\mathrm{~g})}+3 \mathrm{H}_{2(\mathrm{~g})} ightleftharpoons 2 \mathrm{NH}_{3(\mathrm{~g})}$ is $4.28 \times 10^{-5} \mathrm{~atm}^{-2}$ at $725 \mathrm{~K}$, in which direction the net reaction will go ?
  1. Forward
  2. Backward
  3. No net reaction
  4. Direction of reaction cannot be predicted

Solution

$$
\mathrm{O}_{\mathrm{p}}=\frac{\left(\mathrm{P}_{\mathrm{NH}_{3}}ight)^{2}}{\mathrm{P}_{\mathrm{N}_{2}} \times\left(\mathrm{P}_{\mathrm{H}_{2}}ight)^{3}}=\frac{(3)^{2}}{(1)(2)^{3}}=\frac{9}{8} \mathrm{~atm}^{-2}
$$
$$
=1.125 \mathrm{~atm}^{-2}
$$
Since value of $\mathrm{Q}_{\mathrm{p}}$ is larger than $\mathrm{K}_{\mathrm{p}}$ $\left(4.28 \times 10^{-5} \mathrm{~atm}^{-2}ight)$, it indicates net reaction will proceed in backward direction.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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