Final answer:
The equilibrium constant expression for the given reaction is Kc = [CO₂-Hb-H+][O₂] / [HbO₂][H₃O+][CO₂], derived from the law of mass action excluding pure liquids and solids.
Step-by-step explanation:
To write the equilibrium constant expression for the reaction HbO₂ (aq) + H₃O+ (aq) + CO₂(g) = CO₂-Hb-H+ + O₂(g) + H₂O(l), we need to use the law of mass action. This law states that the equilibrium constant (Kc) for a chemical reaction is the ratio of the molar concentrations of the products to the molar concentrations of the reactants, each raised to the power of their respective coefficients in the balanced chemical equation.
The expression for this reaction would be:
Kc = [CO₂-Hb-H+][O₂(g)] / [HbO₂(aq)][H₃O+(aq)][CO₂(g)]
Note that H₂O(l) is not included in the equilibrium expression because the activity of pure liquids (and solids) is taken as 1 and does not affect the value of Kc.