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% purity of iron in cast iron?

ive been set a homework to find out percentage of iron in cast iron via redox titration, im gathering you could determine the mass of iron in a sample of cast iron by titration.
Help with what to use would be extremely helpful.
thanks Roko
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Avatar for vVPiKaVv
vVPiKaVv
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Since it is redox titration, Fe must get oxidised, preferably to Fe (III) ions to prevent discrepancies in results.. A strong oxidising agent, such as acidified potassium permanganate or potassium dichromate, will do the trick.
yeah, weigh out a sample, say 3g, dissolve your sample in sulphuric acid and then make it up to a suitable vollume, say 250cm3. extract 25cm3 portions and titrate with 0.01 mol dm-3 KMnO4 solution (self indicating).

Fe + H2SO4 --> FeSO4 + H2

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

work out moles of (MnO4)- used, then moles of Fe2+, then mass of Fe.

% purity = (mass of Fe in whole sample)/(mass of sample) x 100

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