Question

Determine the empirical formula of an oxide of iron which has 69.9% iron and 30.1% dioxygen by mass.

Answer 1

% of iron by mass = 69.9 % [Given]

% of oxygen by mass = 30.1 % [Given]

Relative moles of iron in iron oxide :-

`="% of iron by mass"/"Atomic mass of iron"`

`=69.9/55.85`

= 1.25

Relative moles of oxygen in iron oxide :-

`="% of oxygen by mass"/"Atomic mass or oxygen"`

`=30.1/16.00`

= 1.88

Simplest molar ratio of iron to oxygen:

= 1.25: 1.88

= 1: 1.5

`~=` 2: 3

∴ The empirical formula of the iron oxide is Fe₂O_3.