The higher the hydronium ion concentration of a solution, the its ph.

a. higher
b. lower

B. Lower

Explanation:

Remember that the pH is calculated as

-log (H30 +)

That is, at a higher concentration of H30 +, with the -log, the pH value decreases and vice versa.

With a concentration 1e-5, it yields a pH of 5.00 and with 1e-2 a value of 2.00

Explanation:

The hydronium ion is [H3O+] or it can be written as [H+].[H2O].

As pH is a measure of the concentration of [H+], pH = -log[H+].

The higher the hydronium ion concentration of a solution, the _Lower_ its pH.

The answer is B.