Question

Assertion :Ammonium sulphate is a better fertiliser than urea. Reason: Urea decomposes to give $N{H}_3$ and $C{O}_2$.

• A. Both assertion and reason are CORRECT and reason is the CORRECT explanation of the assertion.
• B. Both assertion and reason are CORRECT, but reason is NOT THE CORRECT explanation of the assertion.
• C. Assertion is CORRECT, but reason is INCORRECT.
• D. Assertion is INCORRECT, but reason is CORRECT.

Answer 1

The correct option is D Assertion is INCORRECT, but reason is CORRECT.

Urea (carbamide), readily produced from ammonia and carbon dioxide, Urea contains the highest percentage of nitrogen Containing 46% N, it is the most concentrated nitrogen fertilizer, and is readily available as free-flowing prills (granules). It is the cheapest form of nitrogen fertilizer to transport and it is also the least likely to 'cake'. When surface applied, urea is the most readily volatilized of the dry nitrogen materials.
Disadvantages of using ammonium sulfate over urea
1. It only 21% nitrogen (420 lb N/ton).
2. It is much more acidic form of nitrogen and requires 5.35 lbs of pure limestone to neutralize the acidity resulting from 1 lb N as Ammonium Sulphate (compared to only 1.8 lbs of limestone per lb N as urea and other common N sources).
3. It is almost always more expensive per lb of N. Thus urea is better than ammonium sulphate and urea decomposes to ammonia and $C{O}_2$.
Thus, Option D is correct.