Now our A reactant is in the gas state, our B reactor is in the liquid state, our C product is in the Aqueous state and our D product is in the Aqueous state. So let's write the equilibrium constant expression for this reaction. And let's assume that equilibrium has been reached. So our equilibrium constant under standard conditions is equal to the concentration of product C times the concentration of product D divided by the concentration of product A. Now remember, whenever we're writing our equilibrium constant expressions, only aqueous molecules and gas molecules count in our equilibrium expression. We don't include liquid molecules or solid molecules.