Question

A solution of silver nitrate can be used to determine the number of moles of chloride ions in a solution by titration
WHAT is the indicator used in the reaction?
BRIEFLY describe the principle in which the titration is based

Answer 1

When silver nitrate is added to the solution which contains chloride ions, the white precipitate of silver chloride can be formed according to the reaction below:

Ag⁺(aq) + Cl^-(aq) = AgCl(s).

The indicator, which can be used for this reaction, is potassium chromate (K₂CrO₄) dilute solution. After all chloride ions have reacted with silver ions, the remaining part (excess) of silver ions (silver nitrate) can react with chromate ions and red - brown precipitate of silver chromate will be formed accodrind to the reaction below:

Ag⁺(aq) + CrO₄^2-(aq) = Ag₂CrO₄(s).

This is also known as a Mohr's method.