Calculate Kp?

In the heterogeneous equilibrium, only the partial pressures of the gaseous components are involved in the equilibrium expression.

                   2 MgO(s) + 2Cl₂(g) ⇌ 2MgCl₂(s) + O₂(g)
Initial:                             1 mol                          0 mol
Change:                      -0.3 mol                    +0.15 mol
Equilibrium:                  0.7 mol                      0.15 mol

Partial pressure of Cl₂, 𝑃Cl₂ = (1.00 × 10⁵ Pa) × [0.7/(0.7 + 0.15)]= 82350 Pa
Partial pressure of O₂, 𝑃O₂ = (1.00 × 10⁵ Pa) × [0.15/(0.7 + 0.15)] = 17650 Pa
Kp = 𝑃O₂/𝑃Cl₂² = (17650 Pa) / (82350 Pa)² = 2.60 × 10⁻⁵ Pa⁻¹