Question

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

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

Answer 1

Answer: (B)

$\frac{2}{3}$

Given that,
Number of moles of gas, $P_4=3moles$

Number of moles of gas, $P_2=2moles$
Volume of the container, $V=2liter$
Now,
$\left[P_4\right(g\left)\right]=\frac{n_{P_4}}{V}=\frac{3}{2}M$

$\left[P_2\right(g\left)\right]=\frac{n_{P_2}}{V}=\frac{2}{2}M=1M$

Again,
$Q_c=\frac{\left[P_2\right(g){]}^2}{\left[P_4\right(g\left)\right]}$

$=\frac{(1{)}^2}{\left(3/2\right)}$

$=\frac{2}{3}M$