Question

The following questions are based on the preparation of ammonia gas in the laboratory:

1. Explain why ammonium nitrate is not used in the preparation of ammonia.

2. Name the compound normally used as a drying agent during the process.

3. How is ammonia gas collected ? Explain why it is not collected over water. 

Answer 1

1. Ammonium nitrate does not undergo a reversible sublimation reaction, it melts and then decompses into nitrogen oxide gas and water vapour. Thus it is not used in the preparation of ammonia.

NH₄NO₃ → N₂O + 2H₂O

2. Calcium oxide

3. Ammonia is collected in an inverted dry gas jar by downward displacement of air. It is highly soluble in water and hence cannot be collected by downward displacement of water.