Question

$H_2\left(g\right)+S\left(s\right)\rightleftharpoons H_{2}S\left(g\right)$
What is the mass action expression (equilibrium constant expression) for the equilibrium mixture of solid sulfur, hydrogen gas. and hydrogen sulfide gas represented by the equation above?

• A. $K=\frac{1}{\left[H_2\right]}$
• B. $K=\frac{1}{\left[H_{2}S\right]}$
• C. $K=\frac{\left[H_{2}S\right]}{\left[H_2\right]}$
• D. $K=\frac{\left[H_2\right]\left[S\right]}{\left[H_{2}S\right]}$
• E. $K=\frac{\left[H_{2}S\right]}{\left[H_2\right]\left[S\right]}$

Answer 1

The correct option is C $K=\frac{\left[H_{2}S\right]}{\left[H_2\right]}$

The given reaction is :-

$H_2\left(g\right)+S\left(s\right)\rightleftharpoons H_{2}S\left(g\right)$

$\Rightarrow K_C=\frac{\left[H_{2}S\right]}{\left[H_2\right]\left[S\right]}$

$\because$ $S$ is pure solid $\Rightarrow \left[S\right]=1$

$\Rightarrow K_C=\frac{\left[H_{2}S\right]}{\left[H_2\right]}$