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

Ethyne:

• Ethyne is a chemical compound with a molecular formula $\left({\mathrm{C}}_2{\mathrm{H}}_2\right)$.
• It is a colorless gas that is used as fuel.

Reaction of ethyne with Oxygen:

• When ethyne reacts with a mixture of oxygen it produces carbon dioxide along with water.
• The chemical reaction can be depicted as:

$$\begin{gathered} 2\mathrm{HC}\equiv \mathrm{CH}\left(\mathrm{g}\right)+5{\mathrm{O}}_2\left(\mathrm{g}\right)\to 4{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ \left(\mathrm{Ethyene}\right)\left(\mathrm{Oxygen}\right)(\mathrm{Carbon}\mathrm{dioxide})\left(\mathrm{Water}\right) \end{gathered}$$

• A mixture of ethyne and oxygen is used for welding as they both combine completely producing a clean flame.
• When ethyne is burnt with oxygen a high temperature is attained due to the complete combustion of ethyne. Thus, it is used in welding.

A mixture of ethyne and air is not used for welding as no high temperature is being attained when ethyne is burnt with air and it produces a sooty flame.