Q. The equilibrium constants $K_{p_{1}}\ and\ K_{p_{2}}$ for the reactions $X \rightleftharpoons 2Y\ and\ Z \rightleftharpoons P + Q$, respectively are in the ratio of $1:9$. If the degree of dissociation of $X\ and\ Z$ be equal, then the ratio of total pressure at these equilibria is

A) $1:36$
B) $1:1$
C) $1:3$
D) $1:9$
Explanation

(a)
$X\ \ \ \ \ \rightleftharpoons \ \ \ \ \ 2Y$
1 0
At equilibrium $1 - x$ $2x$
Total no. of moles = $1 + x$
$K_{p1} = \frac{\left\lbrack \frac{2x}{1 + x}.p_{1} \right\rbrack^{2}}{\left( \frac{1 - x}{1 + x} \right).P_{1}} = \frac{4x^{2}}{(1 - x)}\ \frac{p_{1}}{(1 + x)}$
$Z\ \ \ \ \ \ \ \ \ \ \ \rightleftharpoons \ \ \ \ \ \ \ \ \ P\ + \ \ \ \mathcal{Q}$
1 0 0
At equilibrium $1 - x$ $x$ $x$
Similarly, $K_{p2} = \frac{x^{2}}{(1 - x)}\ \frac{p_{2}}{(1 + x)}$
$\frac{K_{p1}}{K_{p2}} = \frac{1}{9}$
So, $\frac{4 \times p_{1}}{p_{2}} = \frac{1}{9}$
$\Rightarrow$ $\frac{p_{1}}{p_{2}} = \frac{1}{36}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

Want more practice?
Practice Equilibrium MCQs