Question

A substance with pH 2 is ______ times more acidic than a substance with pH 4.
A. 2
B. 10
C. 100

Answer 1

A. 2

Answer 2

Remember pH is determined by the log-base-10 of the molality of the protons in solution.
\[pH=\log_{10}(m_{H^{+}})\]

For this reason, each pH is separated above and below by a factor of 10 times more basic and acidic respectively.

So for two solutions separated by pH difference of 2, the lower pH is 10^2 times more acidic.

The answer is (C) 100.