Chapter summary
Theories of Acids and Bases, at a glance
Choose the definition that explains the reaction: aqueous ions, proton transfer or electron-pair donation.
A-Level 9476 (2026-2027)
Quick revision
Revisit the essentials, then return to an explanation when you need it.
| Term | Definition to write |
|---|---|
| Arrhenius acid and base | An Arrhenius acid produces H+ ions in aqueous solution; an Arrhenius base produces OH- ions in aqueous solution. |
| Brønsted-Lowry acid and base | An acid is a proton (H+) donor; a base is a proton acceptor. |
| Lewis acid and base | A Lewis acid is an electron-pair acceptor; a Lewis base is an electron-pair donor. |
| Conjugate acid-base pair | Two species that differ by one proton, such as CH3COOH and CH3COO-. |
| Theory | Ask |
|---|---|
| Arrhenius | Does it increase H+(aq) or OH-(aq)? |
| Bronsted-Lowry | Which species donates a proton, and which accepts it? |
| Lewis | Where is the donated electron pair, and which species accepts it? |
A conjugate pair differs by one H+. Water can be acid or base depending on its partner. BF3 accepting a lone pair from NH3 shows why acid-base chemistry is broader than aqueous neutralisation.
Quick recall
State the Arrhenius definitions of an acid and a base.