Question

You heat 3.970 g of a mixture of Fe₃O₄ and FeO to form 4.195 g Fe₂O₃. The mass percent of FeO originally in the mixture was?

Answer 1

You heat 3.970 g of a mixture of Fe3O4 and FeO to form 4.195 g Fe2O3.

The molar masses of Fe3O4, FeO and Fe2O3 are 231.5 g/mol, 71.8 g/mol and 159.7 g/mol respectively.

Let x% be the mass percent of FeO originally in the mixture.

Mass of FeO in original mixture

Mass of Fe3O4 in the mixture

Number of moles of FeO

Number of moles of Fe3O4

Number of moles of Fe2O3 obtained from FeO

Number of moles of Fe2O3 obtained from Fe3O4

Total number of moles of Fe2O3

Total number of moles of Fe2O3

Mass of FeO3 formed

But mass of FeO3 formed is 4.195 g.

Hence,

Hence, the mass percent of FeO originally in the mixture is .