Acid rain (see Chemistry in the Environment box in Section 5.9) over the Great Lakes has

Solution: Here, we are going to calculate the concentration of hydronium ion of rain over the Great Lakes and compare it with that over the West Coast.

Step1:

pH is the negative logarithm to base 10 of hydrogen ion concentration.

pH = - log[H3O+ ]

Step2:

Given, pH of the acid rain over the Great Lakes = 4.5

                                        pH =  - log[H3O+]

Therefore, [H3O+] = 10-pH 

                                                 = 10-4.5

                                            = 3.16 x 10-5

Again, pH of the rain over the West Coast = 5.4

                                        pH =  - log[H3O+]

Therefore, [H3O+] = 10-pH 

                                                 = 10-5.4

                                            = 3.98 x 10-6

Step3:

Thus, the concentration of hydronium ion is higher in the acid rain over the Great Lakes.

Now, [H3O+] over Great Lakes / [H3O+] over the West Coast = (3.16 x 10-5) / (3.98 x 10-6)

                                                                 = 7.93

                                                                  = 8 (approx.)

Thus, the acid in rain over the Great Lakes is approximately 8 times more concentrated.

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