Consider the equilibrium: H2O(l) + HC2H3O2 ⇌ H3O+ + C2H3O2-

( All species are aqueous)

Why will the addition of NaOH to a solution of acetic acid cause the concentration of the acetate ion to increase?

1 answer

More Le Chatelier's Principle. Adding NaOH neutralizes the H3O^+. Decreasing H3O^+ means the equilibrium must shift to the right in order to undo what you just did to the reaction and that increases the acetate.