Question

An oxide of iron contains 69.9% Fe. Determine the empirical formula of the oxide [ Fe= 55.5, O=16]​

Answer 1

Answer:

The iron oxide has 69.9% iron and 30.1% dioxygen by mass.

Thus, 100 g of iron oxide contains 69.9 g iron and 30.1 g dioxygen.

The number of moles of iron present in 100 g of iron oxide are

55.8

69.9

=1.25.

The number of moles of dioxygen present in 100 g of iron oxide are

32

30.1

=0.94.

The ratio of the number of oxygen atoms to the number of iron atoms present in one formula unit of iron oxide is

1.25

2×0.94

=1.5:1=3:2.

Hence, the formula of the iron oxide is Fe

2

O

3

.