Question

The following questions are based on the preparation of ammonia gas in the laboratory:
(a) Explain why ammonium nitrate is not used in the preparation of ammonia.
(b) Name the compound normally used as a drying agent during the process.
(c) How is ammonia gas collected?
(d) Explain why it is not collected over water.

Answer 1

1. • Ammonium nitrate $\left({\mathrm{NH}}_4{\mathrm{NO}}_3\right)$ is not utilized in the manufacture of ammonia because it is explosive and decomposes into nitrous oxide and water vapors.
   • The reactions is as follows:
     ${\mathrm{NH}}_4{\mathrm{NO}}_3\left(\mathrm{aq}\right)\stackrel{∆}{\to }{\mathrm{N}}_2\mathrm{O}\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$
2. • In industrial and chemical operations, a drying agent is a chemical that acts to remove water from a compound that is currently in solution.
   • The quicklime $\left(\mathrm{CaO}\right)$ is basic in nature and does not react with ammonia gas.
   • Thus, quicklime is the compound used as a drying agent during the process.
3. • Ammonia gas $\left({\mathrm{NH}}_3\right)$ is lighter than air.
   • Ammonia gas is highly soluble in water.
   • Hence, ammonia gas is collected by the downward displacement of air in an inverted gas jar.
4. • Ammonia gas is highly soluble in water.
   • Hence, ammonia gas cannot be collected by the downward displacement of water.