why is oxygen a supporter of combustion but does not burn?

Question

please give me a comprehensive ans

Answer 1

When things burn they release energy that was once holding together the molecules of the fuel. In general, it takes a lot of energy to form a molecule of fuel (arbirtary fuel not just automotive fuel) and this energy is measured relative to a particular chemical's common or normal state. Oxygen's normal state is in the diatomic molecule O2 and has a relative energy of zero. In fact all elemental molecules (for example N2, H2, C) have this relative energy, called the enthalpy of formation, of zero. Fuels generally have an enthalpy of formation that is highly negative, which means that it took energy equal to that amount to form the fuel molecules. It also means that because so much energy was put into the fuel molecule, that fuel is highly likely to burn because it is the natural tendency of chemical things to want to reach a more stable state. O2 is already very stable. Its probability of burning is basically zero.

It is also important to look at the characteristics of things that want to burn. If you do that you will find that highly combusable fuels or voliatile ones form stable compounds like CO2, SO2, and H20 after burning. These are the most common products of combustion and are called products of complete combustion. CO2 will be formed when the fuel has as one of its components carbon. When hydrogen is a part of a fuel molecule its will form H20 and when sulfur is part of a fuel (usually coal) it will form S02, sulfur dioxide after combustion.

Oxygen plays a very important role in combustion because the amount of oxygen present during combustion determines which products are made and by that I mean to say that CO, carbon monoxide is actually formed before CO2, and CO2 will only be formed if there is enough oxygen to supply that reaction. remember chemistry class and trying to balance chemical equations? Its just like that. If there are enough moles of oxygen of the left hand side of the equation to support the formation of CO2 then it is usually so. If not, the right hand side will contain amounts of CO2 and CO or just CO. Monatomic carbon, C, graphite--the black soot we see after a fire is also common when sufficient oxygen is not present.

The products of incomplete combustion, CO and SO and H2, are all intermediate forms of fuels (and are unstable fuels themselves with non-positive enthalpies of formation) that remain after combustion if not enough oxygen is present for complete combustion. These are very very bad chemicals for the environment and this is generally why oxygen is a supporter of combustion. With as much as has been found out about the effects of CO2 on global warming and the like it is still a much better chemical to be out there than CO!

Answer 2

oxygen is not fuel .. and a fule requires oxidizer to burn it , it is oxygen in some cases like cyoganic engines it could be nitrogen..

Answer 3

Burning is combining with oxygen to produce heat and light.

Oxygen can not combine with itself !

Answer 4

You can't oxidise oxygen. It is not a fuel.