Question

A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?

Answer 1

When ethyne is burnt in the air, it gives a sooty flame. This is due to incomplete combustion caused by the limited supply of air. However, if ethyne is burnt with oxygen, it gives a clean flame with temperature 3000°C because of complete combustion. This oxy-acetylene flame is used for welding. It is not possible to attain such a high temperature without mixing oxygen. This is why a mixture of ethyne and air is not used.

\[\ce{C2H2_{(g)} + 5/2O2_{(g)} -> 2CO2_{(g)} + H2O_{(l)}}\]