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Chemistry · Glossary

What is Strong and weak acids and bases?

Also known as: strong acid · weak acid · strong base · weak base

Definition 44.6 School Chemistry — Grades 1 to 12 · Chapter 44 — Acids and Bases: Ka and pKa

A strong acid reacts totally with water: none of the acid remains as such in the solution. A weak acid reacts partially: its reaction with water reaches an equilibrium. Likewise a strong base reacts totally with water, a weak base partially.

Examples

Example 44.8 (Hydrochloric acid)

Hydrochloric acid at 0.010 mol/L0.010\,\mathrm{mol}/\mathrm{L}: [HX3OX+]=0.010 mol/L[\ce{H3O+}] = 0.010\,\mathrm{mol}/\mathrm{L} and pH=−log⁡0.010=2.0\mathrm{pH} = -\log 0.010 = 2.0. Diluted ten times, pH 3.0.

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Definition 10.5 University Chemistry — Year 1 · Chapter 10 — Acid–Base Equilibria and the Predominant-Reaction Method

An acid is strong in water if its reaction with water is total: no molecule HA remains (hydrochloric, nitric, perchloric acids, the first acidity of sulfuric acid); otherwise it is weak. A base is strong if its reaction with water is total, giving OHX−\ce{OH-} (hydroxides, the oxide ion, alkoxides), and weak otherwise.

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