Question

The $K_p$ for the reaction; $H_2+I_2\rightleftharpoons 2HI$, at ${460}^{o}C$ is $49$. If the initial pressure of $H_2$ and $I_2$ is $0.5atm$ respectively, determine the partial pressure of each gas at equilibrium.

Answer 1

	$H_2$	$+H_2$	$\rightleftharpoons$	$2HI$
Initial	$0.5$	$0.5$		$0$
At eqm.	$0.5-x$	$0.5-x$		$2x$

$K_p=\frac{(2x{)}^2}{(0.5-x{)}^2}=49$ or $\frac{2x}{0.5-x}=7$
or $2x=3.5-7x$ or $9x=3.5$
or $x=\frac{3.5}{9}=0.39$
$\therefore$ Pressure of $H_2$ and $I_2$ at eqm. $=0.5-0.39$
$=0.11atm$