If a base is added to pure water, why does the [H₃O⁺] decrease?

One of the most acidic lakes in the United States is Little Echo Pond in the Adirondacks in New York. Recently, this lake had a pH of 4.2, well below the recommended pH of 6.5. (10.6, 10.7) a. What are the [H₃O⁺] and [OH⁻] of Little Echo Pond?

In an acidic solution, how does the concentration of H₃O⁺ compare to the concentration of OH⁻?

Calculate the [H₃O⁺] of each aqueous solution with the following [OH⁻]:d. bile, 2.5 x 10⁻⁶ M

Calculate the [H₃O⁺] of each aqueous solution with the following [OH⁻]:a. baking soda, 1.0 x 10⁻⁶ M

State whether each of the following is acidic, basic, or neutral:c. drain cleaner, pH 11.2

Why does a neutral solution have a pH of 7.0?