Question

Equilibrium constant $\left(K_C\right)$ of $2H{I}_{\left(g\right)}\rightleftharpoons H_{2\left(g\right)}+I_{2\left(g\right)}$ is $2\times {10}^{-4}$. What is the equilibrium concentration of $HI$, if concentration of $H_{2\left(g\right)}$ and $I_{2\left(g\right)}$ respectively are $2.2\times {10}^{-2}M$ and $2.2\times {10}^{-4}M$?

• A. $1.55\times {10}^{-1}M$
• B. $2.22\times {10}^{-5}M$
• C. $3.11\times {10}^{-5}M$
• D. $6.66\times {10}^{-5}M$

Answer 1

The correct option is A $1.55\times {10}^{-1}M$

$\begin{array}{c}{K}_C=\frac{\left[H_2\right]\left[I_2\right]}{{\left[HI\right]}^2}=2\times {10}^{-4}\\ {\left[HI\right]}^2=\frac{\left[H_2\right]\left[I_2\right]}{2\times {10}^{-4}}\Rightarrow \frac{2.2\times {10}^{-2}\times 2.2\times {10}^{-4}}{2\times {10}^{-4}}\\ {\left[HI\right]}^2=1.1\times 2.2\times {10}^{-2}\\ \left[HI\right]=\sqrt{2\left(1.1\right)\left(1.1\right)\times {10}^{-2}}\Rightarrow 1.1\times {10}^{-1}\sqrt{2}\Rightarrow 1.55\times {10}^{-1}M\end{array}$