Question

The gas $A_2$ in the left flask allowed to react with gas $B_2$ present in right flask as

$A_2\left(g\right)+B_2\left(g\right)\rightleftharpoons 2AB\left(g\right);K_c=4$ at ${27}^{\circ }$
What is the concentration of $AB$ when equilibrium is established ?

• A. $1.33\text{M}$
• B. $2.66\text{M}$
• C. $0.66\text{M}$
• D. $0.33\text{M}$

Answer 1

The correct option is C $0.66\text{M}$

$\begin{array}{cccccc}& A_2& +& B_2& \rightleftharpoons & 2AB\\ t=0& 2& & 4& & 0\\ \text{at equi.}& 2-x& & 4-x& & 2x\end{array}$
$4=\frac{4x^2}{(2-x)(4-x)}$
$x^2=(4-x)(2-x)$
$\Rightarrow x^2=8-6x+x^2$
$\Rightarrow x=\frac{8}{6}=1.33$
$\Rightarrow \left[AB\right]=\frac{2x}{4}=\frac{x}{2}=0.665$