How do I do redox calculations?
For example,Iron(II) sulphate can be oxidised using acidified potassium permanganate solution. Calculate the mass of iron(II) sulphate which will completely react with 200 cm3 of 0.25 mol l-1 acidified permanganate solution.
Write the redox equation:-2MnO4- + 16H+ + 5Fe2+ à 2Mn2+ + 8H2O + 5Fe3+
Calculate the number of moles of the ‘known’ reactantNo. of moles = C x V(litres)= 0.25 x 0.2 = 0.05 mol
Use: mole ratio in equation to calculate the number of moles ofthe ‘unkown’ reactant.0.05 mol of MnO4- reacts with 5/2 x 0.05 = 0.125 mol of Fe2+
Use: mass = no. of mole x gfm to calculate the mass of iron(II) sulphate Mass of FeSO4 = number of moles x gfmMass of Fe SO4 = 0.125 x152 = 19g
CG
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