Question

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

Answer 1

Explanation:

When ethyne is burnt in air incomplete burning takes place and produce sooty flame due to limited supply oxygen present in the air. However, if ethyne is burnt in oxygen, it gives a clean flame with high temperature (3000°C ) due to complete combustion of ethyne. Hence, This oxy-acetylene flame is used for welding and it is not possible to attain such a high temperature with air. Due this reason a mixture of ethyne and air is not used for welding.

Answer 2

Incomplete Combustion

Explanation:

• Ethyne, also known as acetylene, burns, but how cleanly it burns depends on the availability of oxygen
• Acetylene torch is generally used for welding/cutting metal

Due to limited supply oxygen present in the air ethyne is burnt in air producing sooty flame.

$C_2H_2(g) + O_2(g)$ → $CO(g) + H_2O(g) + C(s) + heat (1)$

The reason is the partial combustion of ethyne

If we add up more oxygen the flame will turn clean blue-white with high temperature (3000°C ).

$2C_2H_2(g) + 5O_2$ → $4CO_2(g) + 2H_2O(g) + lots of heat (2)$

The reason is the complete combustion of ethyne.

∴ This oxy-acetylene flame produced is used for welding and it is not possible to attain such a high-temperature flame in reaction with air.

Thus, a mixture of ethyne and air is not used for welding.