What is the total number of oxygen atoms in 0.200 mol of iron(III) sulfate, Fe2(SO4)3? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
B. 1.45 × 10^24
Principle or equation
Each formula unit of Fe2(SO4)3 contains 12 oxygen atoms (3 sulfate groups × 4 O each). Multiply moles by Avogadro's number and by 12.
Why this answer is correct
Moles of O atoms = 0.200 mol × 12 = 2.40 mol. Number of O atoms = 2.40 × 6.02 × 10^23 = 1.4448 × 10^24 ≈ 1.45 × 10^24.
Example
For 0.100 mol of Na2SO4 (4 O atoms), O atoms = 0.100 × 4 × 6.02 × 10^23 = 2.41 × 10^23.
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