Question

A sample of the black mineral hematite, an oxide of iron found in many iron ores. contains 34.97 g of iron and 15.03 g of oxygen . What is the empirical formula of hematite

Answer 1

Fe = 34.97g

O = 15.03g

Divide by molar mass

Fe = 34.97/56 = 0.624

O = 15.03/16 = 0.939

Divide by smaller number

Fe = 0.624/0.624 = 1

O = 0.939/0.624 = 1.5

Multiply by 2 to turn values to natural numbers

Fe = 2

O = 3

$\therefore$ The empirical formula of the compound is $Fe_2O_3$