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

KMnO4

Oxidising agent

KMnO4 is self indicating

Indicator

colourless to permanent pale pink

Colour change/ How is the end-point detected?

MnO4 - + 5Fe2+ + 8H+ ->Mn2+ + 5Fe3+ + 4H2O

Ionic Equation

1 MnO4- : 5 Fe2+

Ratio

-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

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

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

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

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

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

strong oxidising agent

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

to prevent anaemia

Why are iron tablets sometimes medically prescribed?

Not a primary standard

Why must potassium manganate(VII) solutions be standardised?

unstable

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

ammonium iron (II) sulfate

What reagent is used for this purpose?