Question

How is ethyne prepared in the laboratory?

1. Draw a diagram.
2. Give an equation.
3. How is pure dry gas collected?

Answer 1

Reactants: Water and calcium carbide.

Procedure: Arrange the apparatus as shown in Fig. Take a few pieces of calcium carbide in a conical flask. Add a few drops of water through the thistle funnel. Calcium carbide reacts with water to produce colourless gas with a sweet smelling (ether-like) odour (ethyne gas). The reaction is exothermic.

Reaction:

\[\ce{\underset{carbide}{\underset{Calcium}{CaC2}} + 2H2O -> \underset{hydroxide}{\underset{Calcium}{Ca(OH)2}} + \underset{acetylene}{C2H5 ^}}\]

Collection: The gas is collected by the downward displacement of water since it is insoluble in water.