Acids & Bases Problem Set

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

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.