Compare nitrogen mass percentages using molar masses

Steps:

• Identify nitrogen atoms: all compounds have 2 N atoms (28 g/mol total N mass).
• Apply formula: %N = (28 / molar mass) × 100.
• Calculate: A = 29.2%, B = 21.2%, C = 35.0%, D = 43.8%.
• Select lowest: B at 21.2%.

Why B is correct:

• (NH₄)₂SO₄ has the highest molar mass (132 g/mol) with fixed 28 g N, minimizing %N per the mass percentage formula.

Why the others are wrong:

• A: Lower molar mass (96 g/mol) yields higher 29.2% N.
• C: Lower molar mass (80 g/mol) yields higher 35.0% N.
• D: Lowest molar mass (64 g/mol) yields highest 43.8% N.

Final answer: B