For a hypothetical reaction:
aA ↔ bB
the equilibrium constant is given as:
Keq = [B]^b/[A]^a
activity of pure solids and liquids = 1
For the given reactions:
A) O2(l) ↔ O2(g)
Keq = [O₂]
B) 2O3(g) ↔ 3O2(g)
Keq = [O₂]³/[O₃]²
C) 2H2O(l) ↔2H2(g) + O2(g)
Keq = [H₂]²[O₂]
D) 2Hg(s) + O2(g) ↔ 2HgO(s)
Keq = [Hg]²[O₂]
Ans: A
