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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.

AcidBase
HCL Hydrochloric acid Cl- Chlorine ion
H2SO4 Sulfuric acid HSO4- Hydrogen sulfate ion
HNO3 Nitric acid NO3- Nitrate ion
H3O+ Hydronium ion H2O Water
HSO4- Hydrogen sulfate ion SO42- Sulfate ion
H3PO4 Phosphoric acid H2PO4- Dihydrogen phosphate ion
HC2H3O2 Acetic acid C2H3O2- Acetate ion
H2CO3 Carbonic acid HCO3- Hydrogen carbonate ion
H2S Hydrosulfuric acid HS-
H2PO4- Dihydrogen phosphate ion HPO4+ Hydrogen phosphate ion
NH4+ Ammonium ion NH3 Ammonia
HCO3- Hydrogen carbonate ion CO32- Carbonate ion
HPO42- Hydrogen phosphate ion PO43- Phosphate ion
H2O Water OH- Hydroxide ion
Strength of Conjugate Acid-Base Pairs. Acid strength decreases and base strength increases down the table.