posted by darren on .
The amount of Fe in a 2.0008 g sample of an iron ore was determined by a redox titration with K2Cr2O7. The sample was dissolved in HCl and the iron brought to a +2 oxidation state. Titration required 26.48 mL of 0.034 M K2Cr2O7. Calculate the iron content as %w/w Fe2O3.
Cr2O72- + 14H+ + 6Fe2+ → 2Cr3+ + 7H2O + 6Fe3+
hint: Remember you are looking for Fe2O3 (2 mols of Fe)
mols Cr2O7^2- = M x L = ?
Convert moles Cr2O7^2- to mol Fe.
mols Fe = mols Cr2O7^2- x (6 mol Fe/1 mol Cr2O7^2-) = ? (from the equation)
Convert to moles Fe2O3.
mol Fe x (1 mol Fe2O3/2 moles Fe) = ?
g Fe2O3 = moles Fe2O3 x molar mass = ?
%Fe2O3 = (mass Fe2O3/mass sample)*100 = ?