Redox: Iron in Iron tablets

2009, 2003 - calculations

Why are iron tablets sometimes medically prescribed?

To prevent anaemia

Why must potassium manganate(VII) solutions be standardised?

Not primary standard / to find concentration / reagent impure

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

Unstable / decomposed / affected by light / reacts with water

What reagent is used to standardise the potassium manganate(VII) solution?

Ammonium iron(II) sulfate

Describe how exactly 250cm³ of Fe²⁺ solution was prepared from five iron tablets, each of mass 0.325g.

Tablets crushed in mortar and pestle //

washed into beaker //

stirred to dissolve //

transfer into flask using funnel //

rinsings of beaker added to flask //

fill flask with deionised water until bottom of meniscus is on calibration mark, reading at eye level //

stopper and invert several times

Why was some dilute sulfuric acid used in making up this solution?

Prevents oxidation by air of iron(II)

Explain why additional dilute sulfuric acid must be added to the titration flask before each titration is carried out

To ensure complete conversion of MnO₄^- to Mn²⁺ //

to prevent formation of manganese(IV) / to prevent formation of a brown ppt

How was the end-point detected?

Permanent pale pink colour remains