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Chemistry · Glossary

What is pH-metric titration, half-equivalence?

Also known as: pH-metric titration · half-equivalence

Definition 46.1 School Chemistry — Grades 1 to 12 · Chapter 46 — Titrations by pH and Conductivity

In a pH-metric titration the pH of the titrated solution is measured after each addition of titrant, and the curve pH against the volume added is drawn. Half-equivalence is the point where half the equivalent volume has been added.

A pH-metric titration: the probe dips in the stirred solution, the meter shows the pH after each addition.
A pH-metric titration: the probe dips in the stirred solution, the meter shows the pH after each addition.
Computed pH curves (blue) and their derivative d pH/dV (orange, dotted, divided by 4). Left: 20.0\, mL of hydrochloric acid at 0.100\, mol/ L; equivalence at pH 7.00. Right: 10.0\, mL of diluted vinegar; at half-equivalence the pH equals the pK_a, and equivalence lies at a basic pH.
Computed pH curves (blue) and their derivative d pH/dV (orange, dotted, divided by 4). Left: 20.0\, mL of hydrochloric acid at 0.100\, mol/ L; equivalence at pH 7.00. Right: 10.0\, mL of diluted vinegar; at half-equivalence the pH equals the pK_a, and equivalence lies at a basic pH.
Computed pH curves (blue) and their derivative dpH/dVd\mathrm{pH}/dV (orange, dotted, divided by 4). Left: 20.0 mL20.0\,\mathrm{mL} of hydrochloric acid at 0.100 mol/L0.100\,\mathrm{mol}/\mathrm{L}; equivalence at pH 7.00. Right: 10.0 mL10.0\,\mathrm{mL} of diluted vinegar; at half-equivalence the pH equals the pKapK_a, and equivalence lies at a basic pH.
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