LC CHEMISTRY- DETERMINE THE AMOUNT OF IRON IN AN IRON TABLE (REDOX TITRATION)

Oxidising agent

KMnO4

Indicator

KMnO4 is self indicating

Colour change/ How is the end-point detected?

colourless to permanent pale pink

Ratio

1 MnO4- : 5 Fe2+

Describe in detail the procedure for making up the 250 cm³ solution from the tablets.

crush tablets using a mortar and pestle, using dilute H2SO4, transfer with rinsings to a beaker with some deionised water and dilute H2SO4, stir to dissolve, using a funnel, and transfer solution and rinsings to a 250 cm3 volumetric flask, drop by drop, add deionised water to the volumetric flask until the bottom of the meniscus reaches the graduation mark at eye level, stopper and invert 20 times

Why was it important to use dilute sulfuric acid as well as deionised water in making up the solution from the tablets?

to prevent the oxidation by air of Fe2+ to Fe3+

The reason for adding more dilute sulfuric acid to the conical flask before the titration

to ensure Mn(VII) reduces completely to Mn (II)

Explain why nitric acid could not be used to provide acidic conditions for this reaction.

strong oxidising agent

Why are iron tablets sometimes medically prescribed?

to prevent anaemia

Why must potassium manganate(VII) solutions be standardised?

Not a primary standard

Why was it necessary to standardise the potassium manganate(VII) solution immediately before use in the titration?

unstable

What reagent is used for this purpose?

ammonium iron (II) sulfate