## Acids & Bases Problem Set

### Question 6: Relation between H + and OH - concentrations

Tutorial to help answer the question

If the concentration of H +  in a solution is 10 - 3 M, what will the concentration of OH -  be in the same solution at 25° C?

 A. 10 - 3 M B. 10 - 11 M C. 1011 M D. 2 x 10 - 11 M E. 10 - 14 M

### Tutorial

Relation between H + and OH -  concentrations at 25° C
 In aqueous solutions at 25° C, the product of the H +  and OH -  concentrations is always 10 - 14, as expressed in this equation: [H +] [OH - ] = 10 - 14 This allows calculation of the OH -  concentration if the H +  concentration is known. [OH - ] = 10 - 14 / [H +] [OH - ] = 10 - 14 / 10 - 3 = 10 - 11 This calculation is used when the solution in question is not pure water, but contains some mixture of acids and bases.

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The University of Arizona
January 6, 1999
Revised: October 2004
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