Question

Role of starch as indicator in redox titration

Answer 1

The role of starch as an indicator in redox titrations is explained below:

• Iodometry is a redox titration reaction in which the endpoint is indicated by the release and absorption of iodine due to some reaction.
• Sodium thiosulphate is a reducing agent which reduces the other reactant which is an oxidizing agent and at the endpoint blue color of iodine changed to straw yellow color.
• This color change is due to the presence of starch which we have added before titration in the reaction mixture as an indicator.
• It is used as an indicator because starch is a helix structure that traps the iodine produced at the endpoint and makes the color change from the deep blue of iodine to yellow.
• Starch form a blue color complex with iodine and after reaction or at the endpoint creates yellow color.
• It is used to know the concentration of oxidizing agents.

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