Is diluting an acidic or basic solution with water an effective means of affecting its pH? Why or why not?

Answer 1

Yes. The reason is that water, which also contributes H⁺ and OH^- ions, does not ionize very readily (1x10^-14 is the K_w), so it will not contribute a great deal of H⁺ or OH^-, compared to the acid or base that is contributing H⁺ and OH^- respectively.