IB Chemistry - Acids and Bases

IB Chemistry home > Syllabus 2016 > Acids and Bases > pH curves in itrations

Syllabus ref: 18.3

Titration is an experimental technique whereby a solution is added dropwise from a burette into another solution in a conical flask. It is used to find the concentration of an unknown solution from the stoichiometric quantities of each reagent required for complete reaction (equivalence).

Nature of science:

Increased power of instrumentation and advances in available techniques-development in pH meter technology has allowed for more reliable and ready measurement of pH.


Essential idea: pH curves can be investigated experimentally, but are mathematically determined by the dissociation constants of the acid and base. An indicator with an appropriate end point can be used to determine the equivalence point of the reaction.

The characteristics of the pH curves produced by the different combinations of strong and weak acids and bases.

An acid-base indicator is a weak acid or a weak base where the components of the conjugate acid-base pair have different colours.

The relationship between the pH range of an acid-base indicator, which is a weak acid, and its pKa value.

The buffer region on the pH curve represents the region where small additions of acid or base result in little or no change in pH.

Applications and skills

The general shapes of graphs of pH against volume for titrations involving strong and weak acids and bases with an explanation of their important features.

Selection of an appropriate indicator for a titration, given the equivalence point of the titration and the end point of the indicator.

In Chapter 8.8