What is the mass of nitrogen atoms in 0.250 mol of ammonium sulfate, (NH4)2SO4? (Molar masses: N = 14.0 g/mol, H = 1.0 g/mol, S = 32.1 g/mol, O = 16.0 g/mol)
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Correct answer
A. 7.00 g
Principle or equation
In (NH4)2SO4, there are 2 nitrogen atoms per formula unit. Moles of N = 2 × moles of compound. Mass = moles × molar mass.
Why this answer is correct
Moles of N = 2 × 0.250 = 0.500 mol. Mass of N = 0.500 × 14.0 = 7.00 g.
Example
For 0.100 mol (NH4)2SO4, N moles = 0.200, mass = 2.80 g.
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