Urea, a commonly used nitrogen-based fertiliser, is prepared by the reaction between ammonia and ______.
Answer & explanation
Correct answer: option 1
The correct answer is option 1. carbon dioxide.
The synthesis of urea involves the reaction between ammonia (\(NH_3\)) and carbon dioxide (\(CO_2\)). This chemical process is known as the Bosch–Meiser urea process. Here's an overview of the reaction and the process:
1. Formation of Ammonium Carbamate:
Ammonia gas (\(NH_3\)) is allowed to react with carbon dioxide (\(CO_2\)) in the presence of water (\(H_2O\). The initial reaction involves the formation of ammonium carbamate (\(NH_2COONH_4)).
\[ 2NH_3 + CO_2 + H_2O \rightarrow NH_2COONH_4 \]
2. Formation of Urea:
The ammonium carbamate formed in the first step undergoes further chemical rearrangement to yield urea (\(CO(NH_2)_2\)).
\[ NH_2COONH_4 \rightarrow CO(NH_2)_2 + H_2O \]
3. Overall Reaction
The overall reaction can be represented as follows:
\[ 2NH_3 + CO_2 \rightarrow CO(NH_2)_2 + H_2O \]
4. Process Conditions:
The synthesis typically occurs under high pressure and elevated temperatures to favor the formation of urea. A catalyst, often a compound containing manganese, is used to enhance the reaction rate.
5. Purification:
The urea formed is then purified, often through processes such as crystallization, to obtain the final product in a solid form suitable for use as a fertilizer.
In summary, urea is prepared by reacting ammonia with carbon dioxide in a series of chemical steps known as the Bosch–Meiser urea process. The resulting urea is a valuable nitrogen fertilizer widely used in agriculture.