Question

One of the phenomenon which cannot be described as combustion is:
A) oxidation of coal in air
B) burning of magnesium in nitrogen
C) reaction of antimony in chlorine
D) lighting of an electric lamp

Answer 1

In a combustion process, a substance reacts with oxygen and produces thermal energy. We may say that chemical energy is converted into thermal energy. For example, burning coal, methane gas, and sparklers are all examples of combustion.

Complete answer:
Combustion is a process of high temperature, exothermic, redox chemical reaction. Simply, it is the scientific word for burning. Basically, what happens in a combustion reaction is that a substance reacts with oxygen in the air and transfers energy to the surroundings in the form of heat (produces thermal energy). Also, the things to be noted are that the products of a combustion reaction are called oxides. For example, burning coal, methane gas, and sparklers are all examples of combustion reactions. When the new chemical bonds or the compounds are formed through different chemical reactions, energy is released, which is an exothermic process. So, naturally, during combustion, more energy is released from the new bonds than the basic requirement to break the old bonds. This excess energy keeps the reaction going and produces thermal energy. So, during combustion, chemical energy is converted into thermal energy.

So, the lighting of an electric lamp cannot be described as combustion. The reason is that during the lighting of an electric lamp, the electrical energy is converted into light energy.
Hence the correct answer is option D.

Note:
Burning coal in the air is the major heat source, which is responsible for the spontaneous combustion of coal and also this is one of the most important sources of greenhouse gas emissions. Also, when magnesium is burned in air and reacts with nitrogen, some magnesium nitride is formed in addition to the principal product, magnesium oxide, which proves that it is a combustion reaction. Also, when antimony reacts with chlorine in the air, Antimony trichloride is prepared with antimony trioxide.