What is the total number of oxygen atoms in 0.240 mol of magnesium nitrate, Mg(NO3)2? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
A. 8.67 × 10^23
Principle or equation
Each formula unit of Mg(NO3)2 contains 6 oxygen atoms. Multiply the number of moles by 6 and by Avogadro's constant to get the total number of oxygen atoms.
Why this answer is correct
Moles of O atoms = 0.240 mol × 6 = 1.44 mol. Number of O atoms = 1.44 mol × 6.02 × 10^23 mol^-1 = 8.6688 × 10^23, which rounds to 8.67 × 10^23.
Example
For 0.100 mol of Ca(NO3)2, O atoms = 0.100 × 6 × 6.02 × 10^23 = 3.61 × 10^23.
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