The equilibrium constant (Kp) for the decomposition of gaseous H2O and the equilibrium equation, H2O(g) ⇌ H2(g) + 1/2 O2(g), is related to the degree of dissociation (α) at a total pressure P is given by:

1. Kp = α³P^(1/2)/(1+α)(2+α)^(1/2)
2. Kp = α³P^(3/2)/(1-α)(2+α)^(1/2)
3. Kp = α^(3/2)/P²(1+α)(2+α)^(1/2)
4. Kp = α^(3/2)/P^(1/2)/(1-α)(2+α)^(1/2)