How is titration used to determine the purity of a substance?

Titration is used to determine the purity of a substance by measuring the amount of a solution of known concentration needed to react with it.

In a titration process, a solution of known concentration, called the titrant, is carefully added to a solution of the substance whose purity is being tested, known as the analyte. The titrant is added until the reaction between the two solutions is complete. This point is called the equivalence point or end point, and it is usually indicated by a colour change due to the presence of an indicator.

The purity of the substance can be determined by comparing the volume of titrant needed to reach the equivalence point with the theoretical volume that would be required if the substance was pure. If less titrant is needed, it indicates that the substance is less pure because there are fewer molecules of the substance to react with the titrant. Conversely, if more titrant is needed, it suggests that the substance is more pure.

The concentration of the titrant is known, so the amount of titrant used gives information about the amount of the analyte that reacted. This can be used to calculate the concentration of the analyte, which in turn can be used to calculate the purity of the substance. This is done using the formula: (volume of titrant used x concentration of titrant) / volume of analyte = concentration of analyte.

In summary, titration is a powerful tool in determining the purity of a substance. It involves a reaction between the substance being tested and a solution of known concentration, with the volume of this solution required to complete the reaction providing key information about the purity of the substance.