Mass percent of nitrogen determines nitrogen content in 100g

Steps:

• Calculate molar mass (MM) and nitrogen mass for each formula unit.
• Compute %N = (mass of N / MM) × 100 for each.
• For A (KNO3): MM=101 g/mol, N=14 g, %N=13.9%.
• For B (NH4): MM=18 g/mol, N=14 g, %N=77.8%; for C ((NH4)2SO4): MM=132 g/mol, N=28 g, %N=21.2%; for D ((NH4)H2PO4): MM=115 g/mol, N=14 g, %N=12.2%.
• Highest %N means greatest N mass in 100g.

Why B is correct:

• NH4 formula has single N atom with minimal H mass, yielding highest N fraction per mass percent definition.

Why the others are wrong:

• A: K and O3 add non-N mass, lowering %N.
• C: SO4 group dilutes two N atoms' contribution.
• D: H2PO4 adds significant non-N mass to one N.

Final answer: B