A potassium manganate (VII)/ammonium iron (II) sulphate titration.

Explain why it is necessary

• To use dilute sulfuric acid when preparing the standard solution from hydrated ammonium iron (II) sulfate,

• To add more dilute sulfuric acid to each 25.0cm3 portion of the standard solution used in the titrations.

• To prevent air oxidation of the Fe2+ in solution.

• To ensure MnO4- is reduced to Mn2+

What observations indicate that the correct end point has been reached?

Faint pink colour remains.

What is a standard solution?

Solution of known concentration pure

Give two essential properties of a primary standard for volumetric analysis.

Pure and solid.

Describe fully the procedure used during the titrations to ensure the accuracy of the end point.

• Swirl flask while adding manganate solution from burette.

• Rinse down walls of flask with deionised water.

• Add manganate dropwise as end point is approached.

• Read burette at eye level.

• Carry out a rough titration.

• Repeat to find two more titres that agree to within 0.1 cm3.

• Use a white tile to see colour changes in flask clearly.