Question

One mole of iron III sulfate, Fe2(SO4)3, contains how many moles of SO−24 ions? How many moles of O atoms?

Answer 1

We write down the respective molar masses of the elements in the compound as follows.

Fe = 56

S = 32

O = 16

Molar mass of the iron (iii) Sulphate is given as :

56 × 2 + 3 × 32 + 4 × 3 × 16 = 400 g/mol

Moles of Sulphate ions in the compound is :

Molar mass of Sulphate ions in the compound = 3 × 32 + 12 × 16 = 288

288/400 × 1 = 0.72 moles

The moles of oxygen in the compound is :

Molar mass of oxygen in the compound = 3 × 4 × 16 = 192

192/400 × 1 = 0.48 moles