Question

The equilibrium constant for,
$2H_{2}S\left(g\right)\rightleftharpoons 2H_2\left(g\right)+S_2\left(g\right)$
is 0.0118 at 1300 K while the heat of dissociation is 597.4 kJ. The standard equilibrium constant of the reaction at 1200 K is:

• A. ${10}^{-4}$
• B. ${10}^{-6}$
• C. ${10}^{-8}$
• D. ${10}^{-10}$

Answer 1

The correct option is A ${10}^{-4}$

Using Van't Hoff equation :

$\log \frac{K_2}{K_1}=\frac{\Delta H^{\circ }}{2.303R}[\frac{1}{T_1}-\frac{1}{T_2}]\log \frac{K_2}{0.0118}=\frac{597.4\times {10}^3}{2.303\times 8.314}[\frac{1}{1300}-\frac{1}{1200}]\log K_2=-2+\log \left(0.0118\right)=-3.928\log K_2\approx -4K_2={10}^{-4}$