pH from Hydrogen Ion Concentration
Also known as pH formula · pH from concentration
Worked example: [H+] = 1.0e-3 mol/L → pH = 3 — press Try an example to run it live, then adjust anything.
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The pH scale →
Grade 11Grade 11 Chemistry
The pH scale →
Grade 12Grade 12 Chemistry
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pH from Hydrogen Ion Concentration explained
Hydrogen ion concentrations in water span more than ten orders of magnitude, so in 1909 the Danish chemist Søren Sørensen — working at the Carlsberg brewery laboratory — compressed them onto a logarithmic scale. Each pH unit is a factor of ten: lemon juice at pH 2 carries a hundred times the hydrogen ion concentration of tomato juice at pH 4. Pure water at 25 °C sits at pH 7, where [H⁺] = 1.0 × 10⁻⁷ mol/L. The logarithm takes the concentration in mol/L, and the inverse direction is exact: [H⁺] = .
In water treatment pH is the master variable. Boiler water is typically held between 10.5 and 11.5 to suppress corrosion, cooling towers near 7–9 to balance scale against corrosion, and municipal drinking water around 7.0–8.5. A pH swing of a single unit — a tenfold chemistry change — is often the first sign that a chemical feed pump has failed.
pH from Hydrogen Ion Concentration formula
- = pH
- = Hydrogen ion concentration (M)
Missing one of these? Work it out first, then come back
- Hydrogen ion concentration — Percent Ionization of a Weak Acid, pOH from Hydroxide Ion Concentration