CAIE A-Level Chemistry 7.2.9 pH Titration Curves

Practise sketching and interpreting pH curves for combinations of strong and weak acids with strong and weak alkalis.

Exam points

set the initial pH from acid strength and place the equivalence volume from reacting mole ratios
draw the vertical pH change at equivalence and show how its range depends on acid and base strength
identify the acid–alkali combination from initial pH, buffer-like region and equivalence-point pH

[Maximum number: 1]

Aqueous acid P and aqueous alkali Q have the same concentration.
$20 \mathrm{~cm}^{3}$ of P is added to a conical flask.
Q is slowly added to the flask and the volume of Q and the pH are recorded.
The pH titration curve is shown.

Figure for Question 7.2.9—Sketch the pH titration curves of titrations question 1 — CAIE A-Level Chemistry AS

Which row gives the identity of P and Q ?

HCl

NaOH

$\mathrm{H}_{2} \mathrm{SO}_{4}$

$\mathrm{NH}_{3}$

HCl

$\mathrm{Ba}(\mathrm{OH})_{2}$

$\mathrm{CH}_{3} \mathrm{COOH}$

$\mathrm{Sr}(\mathrm{OH})_{2}$

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7.2.9—Sketch the pH titration curves of titrations question 1