Lab preparation of Ammonia (NH3):
Theory: In the laboratory, a mixture of Ca(OH)2 & NH4Cl is heated in order to produce NH3 gas. In this reaction CaCl2 & water vapor is also produced.
Description of the process: A certain mass of NH4Cl & double of it’s mass of Ca(OH)2 is taken in a boiling tube. A delivery tube is fitted to the mouth of the boiling tube using a cork, & the boiling tube is clamped to a stand.
The open end of the delivery tube is fitted to the lower end of a tower containing dry CaO, which is being used here as a drying agent. Finally, the side tube at the upper part of the tower is inserted into a dry & inverted gas jar.
Now, if the mixture in the boiling tube is heated slowly, wet NH3 is produced.
Drying & collection of wet gas: Water vapor is mixed with the prepared NH3. If tips wet gas is passed through the tower containing CaO (drying agent), the water vapor is absorbed by the CaO & dry NH3 gas is obtained. Since NH3 gas is lighter than air, k can be collected in a dry gas jar by downward displacement of air.
It is dried with CaO (quick lime), because Ca0 and NH3 both are basic compounds so they do not react with each other.
CaO + NH3 —> No reaction
CaO + H2O —> Ca(OH)2