Urea synthesis chemistry — The dehydration of ammonium carbamate to urea is best described as which type of reaction?

Introduction:
In the urea process, the second step converts ammonium carbamate to urea and water. Recognizing the heat effect and equilibrium nature informs heat integration and reactor/stripper design.

Given Data / Assumptions:

• Step 1 (formation of carbamate) is rapid and strongly exothermic.
• Step 2 (dehydration to urea) proceeds more slowly and is reversible.
• Operating at high pressure and moderate temperature in liquid phase.

Concept / Approach:
The dehydration reaction NH2COONH4 ⇌ NH2CONH2 + H2O absorbs heat (endothermic). Higher temperatures favor urea formation but also increase corrosion and side reactions; pressure and NH3/CO2 ratios influence equilibrium by affecting activities. No solid catalyst is used; kinetics depend on solution composition and temperature.

Step-by-Step Solution:
Write reaction: ammonium carbamate → urea + water.Identify heat effect: endothermic (requires heat input).Acknowledge reversibility: equilibrium-limited; stripping removes CO2/NH3 to shift conversions.

Verification / Alternative check:
Energy balances in plant design allocate heat to the reactor/stripper to sustain dehydration; coolant duty is assigned to the upstream exothermic carbamate formation.

Why Other Options Are Wrong:

• “Catalytic” is incorrect; no solid catalyst is employed.
• “Exothermic” swaps the heat effect with step 1.
• “Reversible only” misses the heat effect; while reversible, the key classification here is endothermic.
• Not spontaneous at ambient conditions.

Common Pitfalls:
Conflating the heat effects of the two sequential reactions; assuming catalysts are required because many synthesis processes are catalytic.

Final Answer:
Endothermic (heat is absorbed; equilibrium-limited)