# Does reaction quotient Q take into account pure solids and liquids?

I understand that the equilibrium constant does not take into account the concentrations/ pressures of pure solids and liquids. How about the reaction quotient?

In the following reversible reaction, am I right to say that since water is a pure liquid, it is not reflected in the reaction quotient, hence removing water (without changing the temperature) will not shift the equation left/right after applying Le Chatelier's Principle?

$$\ce{H3PO4 (aq) + H2O <=> H3O+ (aq) + H2PO4- (aq)}$$

• You're wrong, it will. – Mithoron May 17 '16 at 19:14
• @Mithoron: Thank you so much for your reply. Could you help me understand why? Do we actually have to include pure solids/liquids in the reaction quotient Q? Or do do we not use reaction quotient in applying Le Chatelier's Principle? Grateful for your help! – Psteo2891988 May 19 '16 at 3:26
• They shouldn't appear in the reaction quotient, indeed. However, by removing water, you concentrate the solution, which leads to a shift of the equilibrium. – Thomas Jungers May 29 '17 at 11:03

$$K_\mathrm{eq} = \frac{a_\ce{H2PO4-}a_\ce{H3O+}}{a_\ce{H3PO4}a_\ce{H2O}}$$