Question

What is the equilibrium constant expression for the reaction
$P_{4}\left(\right.s\left.\right)+5O_{2}\left(\right.g\left.\right)\rightleftharpoonsP_{4}O_{10}\left(\right.s\left.\right)$

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

Answer 1

Answer: (B)

The concentration of pure solids and liquids do not change with time during the reaction. Thus, in the equilibrium constant expression, their concentration is taken as unity.
For the reaction $P_{4}\left(\right.s\left.\right)+5O_{2}\left(\right.g\left.\right)\rightleftharpoonsP_{4}O_{10}\left(\right.s\left.\right)$
Equilibrium constant is given by
$K_{c}=\frac{\left[\right. P_{4} O_{10} \left]\right.}{\left[\right. P_{4} \left]\right. \left[\right. O_{2} \left]\right.^{5}}$
In equilibrium constant expression, solid and liquid are not considered.
$K_{c}=\frac{1}{\left[\right. O_{2} \left]\right.^{5}}$