Using the law of mass action, write the equiLiBrium expression for each of the following reactions. (a) 3 C₂H₂(g) + 3 H2(g) ⇌ C6H12(f) , (b) CO₂(g) + C(s) ⇌ 2 CO(g) , (c) CF₄(g) + 2 H₂O(l) ⇌ CO₂(g) + 4 HF(g) , (d) K2NiiF6(s) + TiF4(s) ⇌ K2TiF6(s) + NiF2(s) + F2(g)