Conjugate Acids & Bases (DP IB Chemistry) : Revision Note

Conjugate Acids & Bases

• A Brønsted-Lowry acid is a species that can donate a proton

• A Brønsted-Lowry base is a species that can accept a proton

• In an equilibrium reaction, the products are formed at the same rate as the reactants are used

CH₃COOH (aq) + H₂O (l)         ⇌    CH₃COO^- (aq)          +         H₃O⁺ (aq)

         acid                 base                    conjugate base             conjugate acid

• The reactant CH₃COOH is linked to the product CH₃COO^- by the transfer of a proton from the acid to the base

  • Similarly, the H₂O molecule is linked to H₃O⁺ ion by the transfer of a proton

• These pairs are therefore called conjugate acid-base pairs

  • A conjugate acid-base pair is two species that are different from each other by a H⁺ ion

    • Conjugate here means related

    • In other words, the acid and base are related to each other by one proton difference