Redox Titrations

Chemistry page

This is the theory section of redox titrations.
Experiments make up the majority of this section.

Redox Titration  a titration using oxidising and reducing agents

Manganate (VII) – Iron (II) Titrations

Potassium manganate (VII) solution is often used for two reasons

1. It reacts completely
2. It is its own indicator (Colour change from purple to pink)

Potassium Manganate (VII) solution must be standardised before use with a solution of ammonium iron (II) sulfate [primary standard]

Sulfuric acid is added to this redox titration for two reasons

1. It prevents premature oxidation of iron (II) to iron (III)
2. It ensures manganate reduces fully from (VII) to (II) [a brown precipitate indicates manganate (IV)]

Burette readings are taken from the top of the meniscus as the mensicus of potassium manganate (VII) is difficult to see.

This type of titration can be used to find the concentration of iron (II) in a substance e.g. amount of iron in an iron tablet

Iodine-Thiosulfate Titrations

Iodine-thiosulfate titrations are used in volumetric analysis e.g. to determine the percentage of hypochlorite in bleach

A standard solution of iodine can be used to standardise a sodium thiosulfate solution, but the opposite is also true.

Starch is used as an indicator:

Brown >> straw yellow >> starch added >>> blue/black colour >>> colourless