Conjugate acid

In the Brønsted-Lowry (protonic) theory of acids and bases, a conjugate acid is the acid member, HX, of a pair of two compounds that transform into each other by gain or loss of a proton. The base produced, X-, is called the conjugate base. In aqueous solution, the chemical reaction involved is of the form

Related Topics:
Brønsted - Lowry - Protonic - Acids and bases

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:HX + H2O ↔ X- + H3O+

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This principle is discussed in detail in the article on acid-base reaction theories.

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Tabulated below are several examples of conjugate acid-base pairs. Acid strength decreases and base strength increases down the table. (The dissociation reaction reaches equilibrium further to the right, with more X- produced.)

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AcidBase

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HCl Hydrochloric acid

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Cl- Chloride ion

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H2SO4 Sulfuric acid

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HSO4- Hydrogen sulphate ion

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HNO3 Nitric acid

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NO3- Nitrate ion

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H3O+ Hydronium ion

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H2O Water

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HSO4- Hydrogensulphate ion

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SO42- Sulfate ion

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H3PO4 Phosphoric acid

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H2PO4- Dihydrogen phosphate ion

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HC2H3O2 Acetic acid

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C2H3O2- Acetate ion

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H2CO3 Carbonic acid

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HCO3- Hydrogen carbonate ion

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H2S Hydrosulfuric acid

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HS- Hydrogen sulphide ion

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H2PO4- Dihydrogen phosphate ion

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HPO4+ Hydrogen phosphate ion

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NH4+ Ammonium ion

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NH3 Ammonia

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HCO3- Hydrogen carbonate ion

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CO32- Carbonate ion

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HPO42- Hydrogen phosphate ion

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PO43- Phosphate ion

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H2O Water

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OH- Hydroxide ion

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