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 = 10^{log 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

Copyright © 1997-2001 by Fred Senese
Comments & questions to senese@antoine.frostburg.edu
Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101-hidden/acidbase/faq/molarity-and-pH.shtml