How do you determine the end point in a titration?

The end point in a titration is determined when the indicator changes colour, signifying neutralisation has occurred.

In a titration, a solution of known concentration (the titrant) is used to determine the concentration of an unknown solution (the analyte). The end point of a titration is the point at which the reaction between the titrant and the analyte is complete. This is typically indicated by a change in colour of an indicator that has been added to the analyte solution.

The choice of indicator is crucial in determining the end point accurately. The indicator must change colour at a pH that is within the equivalence point of the titration. The equivalence point is the point at which stoichiometrically equivalent amounts of the titrant and analyte have reacted. For example, in an acid-base titration, phenolphthalein is often used as the indicator. It changes colour from colourless to pink as the solution changes from acidic to slightly basic.

During the titration, the titrant is added to the analyte solution gradually. As the titrant is added, the indicator in the analyte solution starts to change colour. However, this colour change is not permanent and reverts back as the solution is still not neutral. The end point is reached when the colour change is permanent, indicating that all of the analyte has reacted with the titrant.

It's important to note that the end point is not always exactly the same as the equivalence point. There may be a slight difference between the two, known as the titration error. However, with careful choice of indicator and precise titration technique, this error can be minimised.

In summary, the end point in a titration is determined by observing the colour change of an indicator added to the analyte solution, which signifies that the reaction between the titrant and the analyte is complete.