The equilibrium constant for the reaction, CaCO3(s) ⇌ CaO(s) + CO2 (g), is
Molar concentration of pure solids or liquids is constant. Therefore [CaCO3(s)] = [ CaO(s)] = 1.
For the reaction CaCO3(s) ⇋ CaO(s) + CO2(g) the partial pressure of CO2 (at equilibrium) depends on: