Complete the reaction
\(NH_2CONH_2 + H_2O \longrightarrow\)
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → NH3, CO2, H2O
Urea is hydrolysed by water (in the soil, by the enzyme urease) to ammonia and carbon dioxide; this is one of the natural sources of ammonia:
\( \ce{NH2CONH2 + 2H2O -> (NH4)2CO3 <=> 2NH3 + H2O + CO2} \)
Why the other options are incorrect
Option (1) NO, H2O, CO — Incorrect. Nitrogen in urea is in the −3 state; hydrolysis is not an oxidation, so NO cannot form.
Option (2) N2O, CO2, H2O — Incorrect. \( \ce{N2O} \) is made by heating \( \ce{NH4NO3} \), not by hydrolysis of urea.
Option (3) HNO3, CO2 — Incorrect. Nitric acid would need oxidation of nitrogen to the +5 state.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Preparation – “Ammonia is present in small quantities in air and soil where it is formed by the decay of nitrogenous organic matter e.g., urea.”
\( \ce{NH2CONH2 + 2H2O -> (NH4)2CO3 <=> 2NH3 + H2O + CO2} \)