Question

The equilibrium $S{O}_2\left(g\right)+1/2O_2\left(g\right)\rightleftharpoons S{O}_3\left(g\right)$ is established in a container of $4\text{L}$ at a particular temperature. If the number of moles of $S{O}_2\left(g\right),O_2\left(g\right)$ and $S{O}_3\left(g\right)$ at equilibrium are $2,1$ and $4$ respectively, then find the value of the equilibrium constant.

• A. 4
• B. 3
• C. 8
• D. 5

Answer 1

The correct option is A 4

Given,
The number of moles of $S{O}_2\left(g\right),O_2\left(g\right)$ and $S{O}_3\left(g\right)$ at equilibrium are $2,1$ and $4$ respectively.
Volume $=4\text{L}$
Concentration in terms of molarity is given by,
$\text{Molarity}=\frac{\text{Number of moles of solute}}{\text{Volume of solution (in L)}}$

	$S{O}_2\left(g\right)+$	$\frac{1}{2}{O}_2\left(g\right)$	$\rightleftharpoons S{O}_3\left(g\right)$
$\text{Moles at equilibrium}$	$2$	$1$	$4$
$\text{Concentration at equilibrium}$	$\frac{2}{4}$	$\frac{1}{4}$	$\frac{4}{4}$
	$0.5$	$0.25$	$1$

The equilibrium constant expression for the given reaction is as fallows;

$K_c=\frac{[S{O}_3{]}_{eq}}{\left[S{O}_2{]}_{eq}\right[O_2{]}_{eq}^{1/2}}\Rightarrow \frac{1}{\left(0.5\right)(0.25{)}^{1/2}}$

$K_c=4$