# Let's improve in Chemistry

Chemistry Level pending

A $$3.00\text{ g}$$ sample containing $$\ce{Fe3O4}$$, $$\ce{Fe2O3}$$ and an inert impure substance, is treated with excess of $$\ce{KI}$$ solution in presence of dilute $$\ce{H2SO4}$$. The entire ion is converted into $$\ce{Fe^{2+}}$$ along with liberation of Iodine. The resulting solution is diluted to $$100\text{ mL}$$. A $$20\text{ mL}$$ of the dilute solution requires $$11.0\text{ mL}$$ of $$0.5\text{ M}$$ $$\ce{Na2S2O3}$$ to reduce iodine present. A $$50\text{ mL}$$ of dilute solution, after complete extraction of Iodine requires$$12.80\text{ mL}$$ of $$0.25\text{ M}$$ $$\ce{KMnO4}$$ solution in dilute $$\ce{H2SO4}$$ medium for oxidation of $$\ce{Fe^{2+}}$$. Calculate the percentage of $$\ce{Fe2O3}$$ in the mixture.

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