Question

The following questions are based on the preparation of ammonia gas in the laboratory: Explain why ammonium nitrate is not used in the preparation of ammonia?

Answer 1

Ammonium nitrate is an inorganic compound. The formula of ammonium nitrate is $N{H_4}N{O_3}$. It is highly soluble in water but does not form hydrates. It is commonly used as fertilizer for nitrogen.

Complete step by step answer:
When Solid ammonium nitrate is very explosive, when heated , it decomposes into gas very rapidly. ammonium nitrate decomposes into nitrous oxide and water vapor.
The reaction of decomposition is
$N{H_4}N{O_3}\left( s \right) \to {N_2}O(g) + 2{H_2}O(g)$.
This decomposition is exothermic with the value of $\Delta H = - 36kJ/mol$.
But this decomposition can be more exothermic up to ${{\Delta H = - 280kJ/mol}}$ with formation of more gaseous product as follows,
$N{H_4}N{O_3}\left( s \right) + C \to {N_2}(g) + 4{H_2}O(g){\text{ }} + C{O_2}(g)$
Due to this reason ammonium nitrate cannot be used in the preparation of ammonia in the laboratory.

Additional information:
The Haber process is used to prepare ammonia. In this reaction nitrogen and hydrogen gas is used and to catalyst the reaction solid iron is used. This mechanism is also exothermic. The reaction is shown below,
${N_2}(g) + 3{H_2}(g)\xrightarrow{{Fe}}2N{H_3}(g)$

Note:
Solid ammonium nitrate decomposes into gas very rapidly. Ammonium nitrate decomposes fully into gaseous products like nitrogen, carbon dioxide, water vapour etc. Ammonia is formed by the Haber process where nitrogen and hydrogen gas is used as reactant and as catalyst solid iron is used.