Question

What is the equilibrium expression for the reaction
$\left(\text{P}\right)_{4} \left(\text{s}\right) + 5 \left(\text{O}\right)_{2} \left(\text{g}\right) \overset{}{\rightleftharpoons} \left(\text{P}\right)_{4} \left(\text{O}\right)_{1} _{0} \left(\text{s}\right) ?$

• A. $K_{C}=\frac{\left[P_{4} O_{10}\right]}{5 \left[P_{4}\right] \left[O_{2}\right]}$
• B. $K_{C}=\frac{1}{\left[O_{2}\right]^{5}}$
• C. $K_{C}=\frac{\left[P_{4} O_{10}\right]}{\left[P_{4}\right] \left[O_{2}\right]}$
• D. $K_{C}=\left[O_{2}\right]^{5}$

Answer 1

Answer: (B)

In the expression for equilibrium constant species in solid state are not written (i.e, their molar concentrations are taken as 1)
$P_{4}\left(s\right)+5O2\left(s\right)\overset{}{\rightleftharpoons}P_{4}O_{10}\left(s\right)$
So $K_{C}=\frac{1}{\left[O_{2}\right]^{5}}$