Chapter summary
Chemistry of Aqueous Solutions, at a glance
Calculate acidity, follow titrations and buffers, and predict whether an ionic solid dissolves or precipitates.
A-Level 9476 (2026-2027)
Quick revision
Revisit the essentials, then return to an explanation when you need it.
| Term | Definition to write |
|---|---|
| Strong acid | An acid that dissociates completely in water. |
| Weak acid | An acid that dissociates only partially in water. |
| pH | pH = -lg[H+]. |
| Buffer solution | A solution that resists a change in pH when a small amount of acid or base is added. |
| Solubility product, Ksp | The product of the concentrations of the ions in a saturated solution of a sparingly soluble salt, each raised to the power of its stoichiometric coefficient, at a given temperature. |
| Common ion effect | The reduction in the solubility of a sparingly soluble salt when a solution containing one of its ions is added. |
- Has acid reacted with base?
Do the mole balance and dilution first.
- Identify what remains
Strong excess: concentration directly. Weak acid/base alone: small-dissociation model. Conjugate pair: buffer ratio.
- Check conditions
Use the stated temperature, correct Kw, justified approximation and relevant indicator range.
Buffers resist small changes by reacting with what is added, but their capacity is limited. Ocean CO2 uptake uses up carbonate and lowers pH. For solubility, compare the free-ion product with Ksp. A common ion reduces dissolving, while forming a complex with a dissolved ion can increase it. Give every K its units (Ka and Kb: mol dm-3; Ksp: count the ions). A p value has no units.
Quick recall
Write Ka for ethanoic acid and give its units.