What is the mass of nitrogen atoms in 0.150 mol of ammonium nitrate, NH4NO3? (Molar masses: N = 14.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol)
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Correct answer
A. 4.20 g
Principle or equation
Each formula unit of NH4NO3 contains two nitrogen atoms. Moles of N atoms = 2 × moles of NH4NO3. Mass of N = moles of N × molar mass of N.
Why this answer is correct
Moles of NH4NO3 = 0.150 mol. Moles of N atoms = 2 × 0.150 = 0.300 mol. Mass of N = 0.300 mol × 14.0 g/mol = 4.20 g.
Example
For 0.100 mol of (NH4)2SO4, there are 2 N atoms per formula unit, so moles N = 0.200, mass N = 0.200 × 14.0 = 2.80 g.
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