Question

How is ethyne (acetylene) prepared in the laboratory?

Answer 1

Ethyne is prepared in the laboratory by the reaction of calcium carbide with water. The equation is:

$\underset{\mathrm{Calcium}\mathrm{carbide}}{{\mathrm{CaC}}_2}+2{\mathrm{H}}_2\mathrm{O}\to \underset{\mathrm{Ethyne}}{{\mathrm{C}}_2{\mathrm{H}}_2}+\mathrm{Ca}(\mathrm{OH}{)}_2$

Take a few pieces of calcium carbide in a conical flask and then add a few drops of water to it. Ethyne gas is produced, which is collected by the downward displacement of water. Arrangement of apparatus is shown in the following figure:



To remove impurities like phosphene, ammonia and hydrogen sulphide from it, ethyne gas is passed through an acidified solution of CuSO₄.