Question

making connections
after dr rustad completed her undergraduate degree, she went to the adirondack mountains in new york with dreams of being a woods woman. she accepted the only open position available, a volunteer technician on an acid rain project. the scientists on this project they studied the lakes in the area and found that they were 100 times more acidic than they were supposed to be. the ph of the water was similar to that of lemon juice. they linked the pollution that caused the high ph levels in the northeast to power plants in the midwest. one of the scientists on the project presented the findings to the u.s. congress. in 1990, the clean air act amendment was passed. as a result, acid rain was reduced by 80%. inspired by this accomplishment, dr rustad decided to go back to school and pursue a career as a scientist.
explain if the lake is 100 times more acidic than it is supposed to be, what does that mean?

Explanation:

The pH scale is logarithmic. A change of 1 unit on the pH scale means a 10 - fold change in acidity or alkalinity. If a lake is 100 times more acidic than it should be, since \(100 = 10\times10\), this means the pH of the lake water is 2 units lower than the normal pH (because a lower pH means more acidity). For example, if the normal pH of the lake water was \(pH = 7\) (neutral), the current pH would be \(pH=7 - 2=5\).

Answer:

It means the pH of the lake water is 2 units lower than the normal pH (due to the logarithmic nature of the pH scale where a factor of 10 change in acidity corresponds to a 1 - unit pH change, and \(100 = 10^{2}\)).