Total elemental percentage of N and P in ammonium phosphate

Steps:

• Identify formula: Ammonium phosphate is (NH₄)₃PO₄.
• Calculate molar mass: N=42, H=12, P=31, O=64; total=149 g/mol.
• Compute N percentage: (42/149) × 100 ≈ 28%.
• Compute P percentage: (31/149) × 100 ≈ 21%; total N + P = 49%.

Why D is correct:

• Nitrogen and phosphorus are key elements for plant growth; their combined mass percentage in (NH₄)₃PO₄ is exactly 49% by atomic weights.

Why the others are wrong:

• A: Matches only N percentage, ignores P.
• B: Matches only N percentage in common fertilizers like DAP, but not total here.
• C: Matches only N percentage in (NH₄)₃PO₄, ignores P.

Final answer: D