Question

Petroleum burns faster than coal. Why?​

Answer 1

Answer:

That is very simple. “burning”, is a chemical reaction of oxidisation. In the case of hydrocarbon fuels the hydrogen component is combined with oxygen to form H2O, water, and the carbon component is combined with oxygen to form CO2, carbon-dioxide, and CO, carbon monoxide. impurities in the fuel such as sulphur, also form sulphurous oxides, and at high temperatures nitrogen in the air can also be oxidised to form nitrogen oxides, sometimes called NOx.

The rate at which the chemical reaction occurs depends on the availability of chemical components to react. Because petrol is a volatile liquid, it forms a petrol and air vapour, which will react readily because all the components for reaction are in close proximity in a large volume. If that vapour is ignited the heat causes the remaining liquid fuel to vaporise so continuing the rapid reaction.

In the case of solid coal, the reactants are only in close proximity at the surface of the coal, and so any initial reaction is slow. Coal, unlike petrol is not a single chemical but a mixture of stuff, so when coal heats up, gas is released, and it is quite a complex chemical process, taking place over a much longer period than the ignition of petrol.