WACE Chemistry — Unit 3
Titration — Flashcards & Quiz
Titration is a quantitative technique for determining an unknown concentration by reacting it with a standard solution of known concentration. WACE Chemistry Year 12 Unit 3 tests both the experimental procedure and the calculation. You need to distinguish equivalence point (stoichiometric) from endpoint (indicator colour change), choose the right indicator based on the pH curve, and perform accurate mole-ratio calculations.
Sample Flashcards
Q1: Describe the key features of a strong acid–strong base titration curve.
The curve has three regions: 1) Gradual pH change far from equivalence point. 2) A steep vertical section at the equivalence point where pH changes rapidly. 3) Gradual change beyond equivalence. Equivalence point pH = 7 (neutral salt formed). The steep region spans roughly pH 3–11, so almost any indicator works.
Q2: How does a weak acid–strong base titration curve differ from a strong acid–strong base curve?
Key differences: 1) Starting pH is higher (weak acid is less dissociated). 2) There is a buffer region before equivalence where pH changes slowly. 3) Equivalence point pH > 7 (the conjugate base of the weak acid is basic). 4) The steep region is shorter (roughly pH 7–11). An indicator with a colour change above pH 7 is needed (e.g. phenolphthalein).
Sample Quiz Questions
Q1: The equivalence point of a strong acid–strong base titration is always at pH 7.
Answer: TRUE
At equivalence, only the neutral salt and water are present. Neither the cation nor anion hydrolyses, so pH = 7 at 25°C.
Q2: The equivalence point of a weak acid–strong base titration is below pH 7.
Answer: FALSE
The equivalence point is ABOVE pH 7 because the conjugate base of the weak acid hydrolyses to produce OH⁻ ions, making the solution basic.
Q3: At the half-equivalence point of a weak acid–strong base titration, pH equals pKa.
Answer: TRUE
At half-equivalence, exactly half the weak acid has been neutralised so [HA] = [A⁻]. By the Henderson-Hasselbalch equation, pH = pKa + log(1) = pKa.
Last updated: March 2026 · 2 flashcards · 3 quiz questions