Question

Give the units of $K_c$ for the formation of 1 mole of ${\mathrm{NH}}_3$ from its constituents.

Answer 1

1. $K_c$ is the ratio of the concentration of products to the product multiplied with the concentration of reactants with all of them raised to the power of their stoichiometric coefficient in the balanced chemical equation.
2. $$\begin{gathered} {\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3\left(\mathrm{g}\right) \\ \mathrm{Nitrogen}\mathrm{Hydrogen}\mathrm{Ammonia} \end{gathered}$$
   $K_c=\frac{{\left[{\mathrm{NH}}_3\right]}^2}{\left[{\mathrm{N}}_2\right]{\left[{\mathrm{H}}_2\right]}^3}$
   $K_c=\frac{{\left(mol{L}^{-1}\right)}^2}{\left(mol{L}^{-1}\right){\left(mol{L}^{-1}\right)}^3}$
3. Thus, unit of $K_c={\mathrm{mol}}^{-2}{\mathrm{L}}^2$.