Chapter summary
Theories of Acids and Bases, at a glance
Follow protons, calculate strong-solution pH and explain how buffers respond to change.
A-Level 8873, revised syllabus (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. |
| Conjugate acid-base pair | Two species that differ by one proton, such as CH3COOH and CH3COO-. |
| Strong acid | An acid that dissociates completely in water. |
| Weak acid | An acid that dissociates only partially in water. |
| pH | pH = -lg[H+]. |
| Ionic product of water, Kw | Kw = [H+][OH-] = 1.00 × 10-14 mol2 dm-6 at 25 °C. |
| Buffer solution | A solution that resists a change in pH when a small amount of acid or base is added. |
| Task | Method |
|---|---|
| Identify conjugate pairs | Species differ by one H+ and one unit of signed charge. |
| Calculate strong-acid pH | Count H+ per formula unit; find concentration; use -log10[H+]. |
| Calculate strong-base pH | Count OH-; use [H+] = Kw/[OH-]; then the logarithm. |
| Mix strong acid and alkali | Neutralise moles first; divide excess by total volume. |
| Choose an indicator | Its transition must lie in the steep supplied pH interval. |
| Explain buffering | Name the component that consumes the added H+ or OH-. |
Quick recall
Define a Bronsted-Lowry acid and base.