A dynamic equilibrium is reached when methane produces hydrogen and ethyne, $\text{C}_2\text{H}_2$. $2CH_4(g) \rightleftharpoons 3H_2(g) + C_2H_2(g)$ What are the units of $K_c$?
- A$\text{mol dm}^{-3}$
- B$\text{mol}^2\,\text{dm}^{-6}$
- C$\text{mol}^3\,\text{dm}^{-9}$
- D$\text{mol}^4\,\text{dm}^{-12}$