Strong and Weak Acids and Bases

A comprehensive tool for understanding strong and weak acids and bases, their dissociation behavior, Ka and pKa values, and examples of each category. Strong acids and bases completely ionize in solution, while weak acids and bases only partially dissociate at equilibrium.

Strong and Weak Acids and Bases

A strong acid or strong base completely ionizes (dissociates) in a solution. In water, one mole of a strong acid HA dissolves yielding one mole of H+ (as hydronium ion H₃O+) and one mole of the conjugate base, A−. Essentially, none of the non-ionized acid HA remains.

A weak acid or weak base only partially dissociates. At equilibrium, both the acid and the conjugate base are present in solution.

Stronger acids have a larger acid dissociation constant (Ka) and a smaller logarithmic constant (pKa = −log Ka) than weaker acids. The stronger an acid is, the more easily it loses a proton, H+.

Strong AcidsFormulaStrong BasesFormula
Hydrobromic acidHBrBarium hydroxideBa(OH)₂
Hydrochloric acidHClCalcium hydroxideCa(OH)₂
Hydroiodic acidHILithium hydroxideLiOH
Nitric acidHNO₃Potassium hydroxideKOH
Perchloric acidHClO₄Sodium hydroxideNaOH
Sulfuric acidH₂SO₄Strontium hydroxideSr(OH)₂
Weak AcidsFormulaWeak BasesFormula
Acetic acidCH₃COOHAmmoniaNH₃
Carbonic acidH₂CO₃Diethylamine(CH₃CH₂)₂NH
Formic acidCHOOHMethylamineCH₃NH₂
Hydrocyanic acidHCNSodium bicarbonateNaHCO₃
Hydrofluoric acidHF
Phosphoric acidH₃PO₄
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pKa--
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Acid Dissociation Constant (Ka)--