The pH is a measure of the concentration of the hydrogen ion (H+) in water. Highly acidic water has a very high H+ concentration, while basic water has very low H+ concentrations. The pH scale is a logarithmic scale, such that a difference of one pH unit means a 10-fold difference in H+ concentration. The mathematical relationship between pH and H+ concentration ([H+]) is pH = –log [H+] OR [H+] = 10-pH where [H+] is in moles per liter.

Use a scientific calculator to calculate [H+] for the following pH values:

7 (a neutral solution)

5.6 (unpolluted rainwater)

3.7 (first acid rain sample in North America)

How many times higher is the concentration of H+ in the Hubbard Brook sample than in unpolluted rainwater?

7 (a neutral solution)
10-7= 0.0000001 moles per liter
5.6 (unpolluted rainwater)
10-5.6 = 0.0000025 moles per liter
3.7 (first acid rain sample in North America)
10-3.7 = 0.00020 moles per liter
The concentration of H+ in the Hubbard Brook sample is 0.00020/0.0000025, which is 80 times higher than the H+ concentration in unpolluted rainwater. (Plato)