Question

The thermodynamic equilibrium constant, $ K_c $ , for the reaction
$ CuO(s) +H_2(g) \rightarrow Cu(s) +H_2O(g) $ is given by

• A. $ K_{c}=\frac{\left[Cu\right]\left[H_{2}O\right]}{\left[CuO\right]\left[H_{2}\right]} $
• B. $ K_{c}=\frac{\left[Cu\right]\left[H_{2}O\right]}{\left[H_{2}\right]} $
• C. $ K_{c}=\frac{\left[H_{2}O\right]}{\left[CuO\right]\left[H_{2}\right]} $
• D. $ K_{c}=\frac{\left[H_{2}O\right]}{\left[H_{2}\right]} $

Answer 1

Answer: (D)

$CuO(s) + H_2(g) \rightleftharpoons Cu(s) + H_2O(g)$
$K_c = \frac {[H_2O]}{[H_2]}$
(As a general rule, the concentration of pure solids and pure liquids are not included when writing an equilibrium equation.)