I'm having some trouble understanding heterogenous equilibria. I read that solids, pure liquids and solvents are omitted from the equilibrium expression. Lets say I have some AgCl in a litre of water. The tiny amount of AgCl that dissociates and dissolved is given by its Ksp. I understand that once a sufficient amount of solid AgCl is present it will give a constant amount of dissociated ions regardless of how much more AgCl is added. What I don't understand is how the solvent (water in this case) is omitted. If I double the volume of water wouldn't I be doubling the amount of dissolved Ag+ and Cl- ions because I would be doubling the amount of solvent for them to dissolve in?