What is the total number of oxygen atoms in 0.300 mol of aluminum sulfate, Al2(SO4)3? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
A. 2.17 × 10^24
Principle or equation
One formula unit of Al2(SO4)3 contains 3 sulfate ions, each with 4 oxygen atoms, so 12 oxygen atoms per formula unit. Multiply moles by Avogadro's number and by the number of atoms per formula unit.
Why this answer is correct
Number of oxygen atoms = 0.300 mol × 12 atoms/formula × 6.02 × 10^23 formula/mol = 0.300 × 12 × 6.02 × 10^23 = 3.6 × 6.02 × 10^23 = 21.672 × 10^23 = 2.1672 × 10^24, which rounds to 2.17 × 10^24.
Example
For 0.100 mol of Na2SO4 (4 O atoms per formula), oxygen atoms = 0.100 × 4 × 6.02 × 10^23 = 2.41 × 10^23.
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