Question

Monoammonium phosphate is produced by reaction of ammonia with

• A. Phosphoric acid
• B. Nitric acid
• C. Sulphuric acid
• D. Hydrochloric acid

Hint:

Think about which acid supplies the phosphate group in the fertilizer.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Monoammonium phosphate, written as \(NH_4H_2PO_4\), is a common water soluble phosphatic fertilizer, and the question asks which acid reacts with ammonia to make it.

Step 2: Key Formula or Approach:
Ammonium phosphate fertilizers are made by neutralizing phosphoric acid with ammonia gas. The ratio of ammonia to acid used decides whether the product is monoammonium phosphate or diammonium phosphate.

Step 3: Detailed Explanation:
Reacting one mole of ammonia with one mole of phosphoric acid gives monoammonium phosphate:
\[ NH_3 + H_3PO_4 \rightarrow NH_4H_2PO_4 \]
Using two moles of ammonia with one mole of phosphoric acid instead gives diammonium phosphate, \((NH_4)_2HPO_4\), a different fertilizer, so this reaction always starts from phosphoric acid regardless of the ammonia ratio.
Nitric acid reacting with ammonia gives ammonium nitrate, not a phosphate fertilizer, so option 2 does not fit.
Sulphuric acid reacting with ammonia gives ammonium sulphate, again not a phosphate fertilizer, ruling out option 3.
Hydrochloric acid reacting with ammonia gives ammonium chloride, which is also not a phosphate salt, ruling out option 4.

Step 4: Final Answer:
Monoammonium phosphate is produced by reacting ammonia with phosphoric acid, so option 1 is correct.