pH Chemistry Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
A solution has pH = 9. Calculate [H+][\text{H}^+] and [OH−][\text{OH}^-].

Solution

  1. 1
    [H+]=10−pH=10−9=1.0×10−9 M[\text{H}^+] = 10^{-\text{pH}} = 10^{-9} = 1.0 \times 10^{-9}\,\text{M}.
  2. 2
    Using Kw=[H+][OH−]=1.0×10−14K_w = [\text{H}^+][\text{OH}^-] = 1.0 \times 10^{-14}:
  3. 3
    [OH−]=1.0×10−141.0×10−9=1.0×10−5 M[\text{OH}^-] = \frac{1.0 \times 10^{-14}}{1.0 \times 10^{-9}} = 1.0 \times 10^{-5}\,\text{M}.

Answer

[H+]=10−9 M,[OH−]=10−5 M[\text{H}^+] = 10^{-9}\,\text{M},\quad [\text{OH}^-] = 10^{-5}\,\text{M}
The product [H+][OH−][\text{H}^+][\text{OH}^-] always equals 10−1410^{-14} at 25°C25°\text{C}. A basic solution has [OH−]>[H+][\text{OH}^-] > [\text{H}^+].

About pH

A logarithmic scale ranging from 0 to 14 that quantifies the hydrogen ion concentration [H+][\text{H}^+] in an aqueous solution, where values below 7 indicate acidic.

Learn more about pH →

More pH Examples

Example 1 easy

Calculate the pH of a solution with [formula].

Example 3 medium

What is the pH of a [formula] HCl solution? (HCl is a strong acid.)

Example 4 medium

Compare a solution with pH 2 and a solution with pH 5. How many times greater is the hydrogen-ion co

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