What is the total number of oxygen atoms in 0.300 mol of iron(III) sulfate, Fe2(SO4)3? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
A. 2.17 × 10^24
Principle or equation
Each formula unit of Fe2(SO4)3 contains 3 sulfate ions, each with 4 oxygen atoms, so 12 oxygen atoms per formula unit. Multiply the number of moles by 12 and by Avogadro's constant to get the total number of oxygen atoms.
Why this answer is correct
Moles of O atoms = 0.300 mol × 12 = 3.60 mol. Number of O atoms = 3.60 mol × 6.02 × 10^23 mol^-1 = 2.167 × 10^24 ≈ 2.17 × 10^24.
Example
For 0.100 mol of Al2(SO4)3, O atoms = 0.100 × 12 × 6.02 × 10^23 = 7.22 × 10^23.
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