A friend of mine insists that there are cases where a reactant or product in a liquid state is used in the equilibrium constant calculation ( the equilibrium constant Kc, Kc = [products]/[reactants]). And I believe that no, a liquid or a solid do not take part in the calculation of Kc, ever.
I've read in many places, that a pure liquid or a pure solid do not take part in the calculation of Kc. So that refers to any reactant or product that has an (l) or an (s) after their chemical formula in the chemical equation, right? We can't have a represention of "chemical formula (l)" without the substance being pure, can we? For example if the substance is potassium chloride, KCl, if KCl(l) appears in a chemical equation, the potassium chloride is pure because if it wasn't the chemical formula wouldn't be KCl, it would be a solution, not a substance. So any product or reactant with an (l) after is a pure liquid and will not take part in the calculation of Kc. Am I correct or nah?