Determine the equilibrium law expression for homogeneous and heterogeneous systems.

The combustion of methane can be represented by the following equilibrium: $\mathrm{CH_4(g) + 2O_2(g) \rightleftharpoons CO_2(g) + 2H_2O(g)}$ (a) Write the equilibrium law expression $(K_c)$ for this reaction. (1 mark) (b) State whether this is a homogeneous or heterogeneous equilibrium system, and justify your answer. (1 mark)

Determine the equilibrium law expression $K_c$ for the following reaction at constant temperature: $$\text{2SO}_3(g) \rightleftharpoons \text{2SO}_2(g) + \text{O}_2(g)$$

Determine the equilibrium constant expression $( K_c )$ for the reaction: $$\text{PCl}_5(g) \rightleftharpoons \text{PCl}_3(g) + \text{Cl}_2(g)$$