Chapter 15

Q. 15.7

Acid rain is a matter of serious concern because most species of fish die in waters having a pH lower than 4.5 – 5.0. Calculate the H_{3}O^{+} concentration in a lake that has a pH of 4.5.


Calculate the H_{3}O^{+} concentration by taking the antilogarithm of the negative of the pH.

Known Unknown
pH = 4.5 [H_{3}O^{+}]


Verified Solution

[H_{3}O^{+}]= antilog  (-pH)=10^{-pH}=10^{-4.5}=3\times 10^{-5}  M

[H_{3}O^{+}] is reported to only one significant figure because the pH has only one digit beyond the decimal point. (If you need help in finding the antilog of a number, see Appendix A.2.)