Question

A 29.7 g sample of iron ore is treated as follows. The iron in the sample is all converted by a series of chemical reactions to Fe₂O₃. The mass of Fe₂O₃ is measured to be 15.6 g. What was the mass of iron in the sample of ore? Answer in units of g.

Answer 1

Answer: The mass of iron in the ore is 10.9 g

Explanation:

We are given:

Mass of iron (III) oxide = 15.6 g

We know that:

Molar mass of Iron (III) oxide = 159.69 g/mol

Molar mass of iron atom = 55.85 g/mol

As, all the iron in the ore is converted to iron (III) oxide. So, the mass of iron in iron (III) oxide will be equal to the mass of iron present in the ore.

To calculate the mass of iron in given mass of iron (III) oxide, we apply unitary method:

In 159.69 g of iron (III) oxide, mass of iron present is $(2\times 55.85)=111.7g$

So, in 15.6 g of iron (III) oxide, mass of iron present will be = $\frac{111.7g}{159.69g}\times 15.6g=10.9g$

Hence, the mass of iron in the ore is 10.9 g