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3.1.8—pH curves

Syllabus
First assessment 2025
Objective
3.1.8
Level
SL

Strong-Acid–Strong-Base Titration Curves

The equivalence point is where stoichiometric amounts of analyte and titrant have reacted. A monoprotic strong-acid–strong-base curve has a steep neutral region centred at the equivalence point.

Read the initial pH, steep intercept region and final plateau; curve direction depends on whether acid or base is added.

For a strong acid titrated with strong base at 25 °C, calculate the initial pH from excess acid, locate equivalence from stoichiometric moles, and place the steep section around pH 7. Equivalence is a mole condition; it is not the same as equal solution volumes unless concentrations and stoichiometry make it so.

Interpreting a Strong Titration Curve

Assessment in practice

Representative question

Question 1

[Maximum number: 1]

Which graph would be obtained by adding 0.10moldm−3HCl(aq)0.10 \mathrm{moldm}^{-3} \mathrm{HCl}(\mathrm{aq}) to 25 cm325 \mathrm{~cm}^{3} of 0.10moldm−3NaOH(aq)0.10 \mathrm{moldm}^{-3} \mathrm{NaOH}(\mathrm{aq}) ?

A
B
C
D

Proton Transfer Reactions Summary

Retrieve the route: track proton transfer and conjugates, calculate pH and Kw, distinguish strength, balance neutralization, read titration curves, use Ka/Kb and hydrolysis, select indicators, and explain and calculate buffer behaviour.

Check donor versus acceptor, one-proton differences, logarithm direction, ion comparison, strength versus concentration, equivalence versus endpoint, pKa landmarks, conjugate equations and dilution ratios.