The equilibrium constant : Kc=[CO₂]
Further explanation
The equilibrium constant is the value of the product in the equilibrium state of the substance in the right (product) divided by the substance in the left (reactant) with the exponents of each reaction coefficient
The equilibrium constant is based on the concentration (Kc) in a reaction
pA + qB -----> mC + nD
Solid (s) and liquid (l) are not included in the calculation of Kc(only aq-aquoeus and g-gas)
From reaction
CaCO₃(s)⇔CaO(s)+CO₂(g)
Because CaCO₃ and CaO are solid, only CO₂ is included in the calculation