Answer
adding an acid to water increases the concentration of the H3O+ ion. decrease in the concentration of the OH- ion.
Explanation/ complete answer
Adding an acid to water therefore has an effect on the concentration of both the H3O+ and OH- ions. Because it is a source of this ion, adding an acid to water increases the concentration of the H3O+ ion. Adding an acid to water, however, decreases the extent to which water dissociates. It therefore leads to a significant decrease in the concentration of the OH- ion.
