Introduction
In a titration a fast reaction is carried out in solution, one reactant being added dropwise from a burette to the other in a flask.
The acid–base reaction shown below can be carried out by titration, provided pKa of the acid is less than 9.
Reaction 1: HA + OH – → H2O + A–
At an equivalence point in a titration of a monoprotic acid is when exactly enough OH – has been added to remove the one acidic hydrogen. The equivalence point can be detected by
- an indicator that changes colour at the pH of the equivalence point solution.
- a titration curve that plots pH vs. volume of added base.
The titration curve is a plot of pH against volume of added titrant.
For the titration of aqueous sodium hydroxide with an aqueous acid,
the curve is fairly flat before equivalence
This is known as the buffer region, and the solution has both the acid and conjugate base as major species. Place your mouse over the curve.
the pH rises steeply at equivalence.
At the equivalence point the conjugate base is the major solute (species in solution).