Question

For commercial production of DAP (Diammonium phosphate), liquid ammonia is reacted with mineral acid

• A. Nitric acid (\(\text{HNO}_3\))
• B. Sulphuric acid (\(\text{H}_2\text{SO}_4\))
• C. Hydrochloric acid (\(\text{HCl}\))
• D. Phosphoric acid (\(\text{H}_3\text{PO}_4\))

Hint:

To remember chemical fertilizer compositions:
- Ammonia + Nitric Acid \(\rightarrow\) Ammonium Nitrate
- Ammonia + Sulphuric Acid \(\rightarrow\) Ammonium Sulphate
- Ammonia + Phosphoric Acid \(\rightarrow\) Ammonium Phosphate (DAP/MAP)

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Diammonium phosphate (DAP) is a widely used phosphatic fertilizer containing \(18\%\) Nitrogen and \(46\%\) \(\text{P}_2\text{O}_5\). It is synthesized by neutralizing phosphoric acid with ammonia.

Step 2: Detailed Explanation:
1. In commercial production, anhydrous liquid ammonia (\(\text{NH}_3\)) is reacted with phosphoric acid (\(\text{H}_3\text{PO}_4\)) in a reactor: \[ 2\text{NH}_3 + \text{H}_3\text{PO}_4 \rightarrow (\text{NH}_4)_2\text{HPO}_4 \] 2. The reaction is highly exothermic and managed under controlled temperature and pH to optimize the production of the diammonium form rather than monoammonium phosphate (MAP).
3. The resulting slurry is granulated and dried to produce agricultural-grade DAP.

Step 3: Final Answer:
The mineral acid used in the commercial manufacture of DAP is phosphoric acid (\(\text{H}_3\text{PO}_4\)).