Question

A mixture of ethyne and oxygen is burnt for welding. In your opinion, why cannot we use a mixture of ethyne and air for this purpose

Answer 1

Ethyne burns in air with a sooty flame because of incomplete combustion caused by the limited supply of air. Bur when burnt at 3000^oC in oxygen it gives a clean flame because of complete combustion. This oxy-acetylene flame is used for welding. Such a high temperature cannot be achieved without mixing oxygen. Therefore, a mixture of ethyne and air is not used for welding.