How is [H+] found from pH?

How do you determine concentration of hydrogen ions when given the pH of a solution?
Mamuke, Illinois State University

Vocabulary
pH*
molarity*
A simple, working definition of pH is [1]

pH = - log[H+]

To obtain the hydrogen ion molarity from the pH, remember that a logarithm of a number is really just the exponent when that number is written as a power of ten:

x = 10log x
so the definition of pH solved for hydrogen ion molarity is
[H+] = 10-pH
For example, the molarity of hydrogen ions in a pH 5 solution is 10-5 M.

Notes

  1. pH is only approximately equal to minus the log of the hydrogen ion molarity. For details, see "What is pH?"

Author: Fred Senese senese@antoine.frostburg.edu



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Last Revised 08/17/15.URL: http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/print-molarity-and-pH.shtml