A mixture of FeO and Fe2O3 contains 75.0% Fe by mass. The mass percentage of Fe2O3 in the mixture is (Fe = 56, O = 16)

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JEE Advanced levelSingle correct optionDifficulty 3 of 3mc180

A mixture of $FeO$ and $Fe X_{2} O X_{3}$ contains $75.0%$ Fe by mass. The mass percentage of $Fe X_{2} O X_{3}$ in the mixture is (Fe = 56, O = 16)

A $64.3%$
B $50.0%$
C $35.7%$
D $7.1%$

Answer: C

Fe fraction in FeO = 56/72 = 0.7778; in Fe2O3 = 112/160 = 0.7000. Let w be the mass fraction of FeO: 0.7778w + 0.7000(1 - w) = 0.750, so w = 0.6429. Fe2O3 fraction = 0.3571, i.e. 35.7%.

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A mixture of FeO and FeX2​OX3​ contains 75.0% Fe by mass. The mass percentage of FeX2​OX3​ in the mixture is (Fe = 56, O = 16)

Answer: C

More questions on Empirical and molecular formula, percentage composition

A mixture of $FeO$ and $Fe X_{2} O X_{3}$ contains $75.0%$ Fe by mass. The mass percentage of $Fe X_{2} O X_{3}$ in the mixture is (Fe = 56, O = 16)