Question

The equilibrium constant $K_c$ for the reaction $P_4\left(g\right)\rightleftharpoons 2P_2\left(g\right)$ is 1.4 at ${400}^{o}C.$ Suppose that 3 moles of $P_4$ (g) and 2 moles of $P_2\left(g\right)$ are mixed in 2 litre container at ${400}^{o}C.$ What is the value of reaction quotient (Q)?

• A. $\frac{3}{2}$
• B. $\frac{2}{3}$
• C. 1
• D. None of these

Answer 1

The correct option is B $\frac{2}{3}$

$P_4\left(g\right)\rightleftharpoons 2P_2\left(g\right)$
Reaction Quotient $Q_c$: $Q_c=\frac{\left[P_2\right(g){]}^4}{\left[P_4\right(g\left)\right]}=$
$Q_c=\frac{(\frac{n_{P_2}}{V}{)}^4}{\frac{n_{P_4}}{V}}=$
$\frac{n_{P_2}}{V}$ = $\frac{2}{2}=1$
$\frac{n_{P_4}}{V}=\frac{3}{2}$
$Q_c=\frac{\left[P_2\right(g){]}^4}{\left[P_4\right(g\left)\right]}=\frac{(1{)}^2}{\left(3/2\right)}=\frac{2}{3}$