In the urea process, which product results directly from the dehydration of ammonium carbamate under high-pressure reactor conditions?

Introduction / Context:
Commercial urea manufacture proceeds by first forming ammonium carbamate from ammonia and carbon dioxide, followed by its dehydration to urea and water. Understanding this step is fundamental in nitrogenous fertilizer technology and plant troubleshooting.

Given Data / Assumptions:

• Feed mixture at high pressure contains NH3 and CO2.
• Ammonium carbamate is the intermediate species.
• Reaction pathway: carbamate → urea + H2O (endothermic dehydration).

Concept / Approach:
The net reaction to urea is 2 NH3 + CO2 → NH2CONH2 + H2O via the carbamate intermediate. Biuret forms only as a side product by condensation of urea molecules at higher temperatures or prolonged residence. “Ammonia water” is not a process product of the dehydration step; rather, excess NH3 is recovered in recycle sections.

Step-by-Step Solution:
Form ammonium carbamate in the reactor from NH3 and CO2.Apply dehydration (heat/pressure conditions) to convert carbamate to urea + water.Recognize that biuret requires urea–urea condensation, not direct carbamate dehydration.Therefore, the direct product is urea.

Verification / Alternative check:
Process flow diagrams show high-pressure synthesis leading to urea solution, followed by recovery/stripping and finishing; biuret control is a specification issue in prilling/granulation, not the primary synthesis step.

Why Other Options Are Wrong:
Biuret: secondary byproduct from urea, not from carbamate dehydration.Ammonia water: not a defined product of the key dehydration reaction.“None of these” is incorrect because urea is correct.

Common Pitfalls:
Confusing the intermediate (carbamate) with byproducts; assuming higher temperature necessarily improves conversion without raising biuret formation.

Final Answer:
Urea