83. How many percent of iron is contained in hematite,

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83. How many percent of iron is contained in hematite, if the titration of 50.00 cm3 of a solution obtained from a weighed portion of 1.00 g, dissolved in acid and diluted in a volumetric flask with a capacity of 250 cm3 requires 20.50 cm3 of KMnO4 solution with C (1 / 5KMnO4 ) = 0.1217 mol / dm3.