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Q 1119856719.     A 3.00 g sample containing `Fe_3O_4, Fe_2O_3` and an inert impure substance is treated with excess of KI solution in presence of dilute `H_2SO_4`. The entire iron is converted into `Fe^(2+)` along with the liberation of iodine. The resulting solution is diluted to 100 mL. A 20 mL aliquot of the diluted solution requires 11.0 mL 0.5 M `Na_2S_2O_3` solution to reduce the iodine present. A 50 mL of the diluted solution after complete extraction of the iodine requires 12.80 mL of 0.25 M `K.MnO_4` solution in dilute `H_2SO_4` medium for the oxidation of `Fe^(2+)`. What is the percentage of `Fe_2O_3` in the original sample?
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