Why does ethyne (acetylene) burn with a sooty flame?
Hint :We know that in order to solve this question, firstly we must know the concept of complete combustion and incomplete combustion. Then we will do both the reactions of ethane with oxygen and ethane with air to check where the complete combustion occurs to get the required result.
Complete Step By Step Answer: We must know complete combustion of ethane and incomplete combustion of ethane to proceed towards the answer. The complete combustion of ethane a combustion reaction has a general reaction of fuel and oxygen to form carbon dioxide and hydro-oxide. Incomplete combustion of ethane. Ethyne undergoes incomplete combustion to form carbon dioxide, carbon monoxide and water vapour. Now, when ethyne (acetylene) is burnt in air, it produces a sooty flame. This is due to incomplete combustion caused by the limited supply of oxygen present in the air that is not enough to melt metals for metals. This oxy-acetylene flame is used for welding and it is not possible to attain such a high temperature with air or without mixing oxygen. Due to this reason, a mixture of ethyne and air is not used for welding whereas mixture ethyne burnt in oxygen is used for welding purposes. Therefore, Ethyne (acetylene) burns with a sooty flame because ethyne is an unsaturated hydrocarbon and the percentage of carbon in these hydrocarbons is comparatively higher which does not get oxidised completely in oxygen or air.
Note : Remember that whenever we face such a type of problem, one can get confused with complete combustion and incomplete combustion so we must know the difference between complete combustion and incomplete combustion to get the required result.