Question

The degree of dissociation of $PC{l}_5\left(\alpha \right)$ obeying the equilibrium,

$PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right)$,

is approximately related to the pressure at equilibrium by :

• A. $\alpha \propto P$
• B. $\alpha \propto \frac{1}{\sqrt{P}}$
• C. $\alpha \propto \frac{1}{P^2}$
• D. $\alpha \propto \frac{1}{P^4}$

Answer 1

Answer: (B)

$\alpha \propto \frac{1}{\sqrt{P}}$

$PC{l}_5\rightleftharpoons PC{l}_3+C{l}_2$

$1$ 0 0
$1-\alpha$ $\alpha$ $\alpha$

$K_p=\frac{{\alpha }^2}{(1-\alpha )}\left[\frac{P}{1+\alpha }\right]=\frac{{\alpha }^{2}P}{1-{\alpha }^2}$

$\alpha =\sqrt{\frac{K_p}{P}}$ if $1-{\alpha }^2=1$

Hence, option B is correct.