Edexcel A Level Chemistry:复习笔记5.2.1 Brønsted–Lowry Acids & Bases

• The Brønsted-Lowry Theory defines acids and bases in terms of proton transfer between chemical compounds
• A Brønsted acid is a species that can donate a proton
  • For example, hydrogen chloride (HCl) is a Brønsted acid as it can lose a proton to form a hydrogen (H+) and chloride (Cl-) ion

HCl (aq) → H+ (aq) + Cl- (aq)

• A Brønsted base is a species that can accept a proton
  • For example, a hydroxide (OH-) ion is a Brønsted base as it can accept a proton to form water

  OH- (aq) + H+ (aq) → H2O (l)

• Conjugate acid-base pairs are a pair of reactants and products that are linked to each other by the transfer of a proton
• In a reaction equilibrium 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
  • Conjugate here means related
  • In other words, the acid and base are related to each other by one proton difference