Evaluating nitrogen compounds as fertilizers based on use and properties

Steps:

• Identify if each compound is used as fertilizer and verify the stated reason against chemical facts.
• For A, check pH effect: ammonia solutions are basic, so assess if it lowers pH.
• For B, confirm solubility: test if NH4Cl dissolves in water per solubility rules.
• For C, examine usage and production: determine if it's unsuitable due to synthesis or stability.
• For D, validate fertilizer role, production via Haber process, and solubility for nutrient delivery.

Why D is correct:

• Ammonium nitrate (NH4NO3) is a standard fertilizer providing N from Haber-derived ammonia and HNO3, with high water solubility (formula enables ionic dissociation for soil uptake).

Why the others are wrong:

• A: Aqueous ammonia (NH3(aq)) is basic and raises soil pH, does not lower it.
• B: NH4Cl is highly soluble in water, contrary to the claim.
• C: (NH4)2CO3 is unstable and decomposes, but the incomplete reason about production is irrelevant; it's not commonly used due to volatility.

Final answer: D