Question

$2S{O}_2+O_2\rightleftharpoons 2S{O}_3$

For the given reaction, the units of $K_c$ are:

• A. mole / litre
• B. litre / mol
• C. mole${}^2$ / lit${}^2$
• D. lit${}^2$ /mole ${}^2$

Answer 1

The correct option is B litre / mol

The unit of the equilibrium constant $K_c$ is $(mole/litre{)}^{\Delta n}$.

Here, $\Delta n$ is the difference in the total number of gaseous products and the total number of gaseous reactants.

For the reaction $2S{O}_2+O_2\leftrightharpoons 2S{O}_3$, $\Delta n=2-(2+1)=-1$.

Hence, the unit of the equilibrium constant $K_c$ will be $(mole/litre{)}^{\Delta n}=(mole/litre{)}^{-1}=litre/mol$.

Hence, the correct option is $\text{B}$