Question

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

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

Answer 1

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

For $P_4\left(s\right)+5O_2\left(g\right)\rightleftharpoons P_4{O}_{10}\left(s\right)$
$K_c=\frac{\left[P_4{O}_{10}\right]\left[P_4\right]}{\left[O_2{)}^5\right]}$
The solids have concentration unity
so, $K_c=\frac{1}{\left[O_2{)}^5\right]}.$