For homogeneous gas reaction

$4{\mathrm{NH}}_3+5{\mathrm{O}}_2 \rightleftharpoons 4\mathrm{NO} + 6{\mathrm{H}}_2\mathrm{O}.$ The equilibrium constant ${\mathrm{K}}_{\mathrm{C}}$ has the unit of

$$\begin{gathered} 4{\mathrm{NH}}_3\left(\mathrm{g}\right)+5{\mathrm{O}}_2\left(\mathrm{g}\right) \rightleftharpoons 4\mathrm{NO}\left(\mathrm{g}\right) + 6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ \mathrm{at} \mathrm{equilibrium} \mathrm{x} \mathrm{x} \mathrm{x} \mathrm{x} \end{gathered}$$

$$\begin{gathered} {\mathrm{K}}_{\mathrm{C}}=\frac{{\left(\mathrm{x}\right)}^4 \times {\left(\mathrm{x}\right)}^6}{{\left(\mathrm{x}\right)}^4 \times {\left(\mathrm{x}\right)}^5}= \left(\mathrm{x}\right)=\mathrm{concentration} \\ {\mathrm{K}}_{\mathrm{C}}=\left(\mathrm{x}\right) \end{gathered}$$