Question

The equilibrium constant for the reaction
$P_4\left(s\right)+5O_2\left(g\right)\rightleftharpoons P_4{O}_{10}\left(s\right)$ is :

• A. $K_c=\frac{1}{{\left[O_2\right]}^5}$
• B. $K_c={\left[O_2\right]}^5$
• C. $K_c=\frac{\left[P_4{O}_{10}\right]}{5\left[P_4\right]\left[O_2\right]}$
• D. $K_c=\frac{\left[P_4{O}_{10}\right]}{\left[P_4\right]{\left[O_2\right]}^5}$

Answer 1

The correct option is A $K_c=\frac{1}{{\left[O_2\right]}^5}$

$P_4\left(s\right)+5O_2\left(g\right)\rightleftharpoons P_4{O}_{10}\left(s\right)$
$K_c=\frac{1}{{\left[O_2\right]}^5}$; note that the expression does not involve the concentration terms of solid species.