Question

Which of the following is a non-combustible substance?
A.Coke
B.Diamond
C.Coal
D.wood

Answer 1

Combustible substances: They are those substances which burn in air and tend to produce heat and light, are known as combustible substances. For example: fuels.
Non-combustible substances: They are those substances which are not combustible in the presence of air, are known as non-combustible substances. For example: Glass, stones.

Complete step by step solution:
Let us first talk about combustible and non-combustible substances.
Combustible substances: They are those substances which burn in air and tend to produce heat and light, are known as combustible substances. For example: fuels. The necessary ingredients for combustion of molecules are heat, fuel and air. On combustion heat and light are produced as products.
Non-combustible substances: They are those substances which are not combustible in the presence of air, are known as non-combustible substances. For example: Glass, stones.
In the question we are given with the compounds coal, coke, wood and diamond.
Now we know that coal, coke and wood are known as fossil fuels and are used for cooking purposes also. These compounds on heating form carbon dioxide as the main product.
So the substance which is non-combustible is diamond.

Hence, option B is correct.

Additional information:
Combustion is defined as a process in which a substance reacts with oxygen and gives heat and light.
Exothermic reactions: They are defined as the reaction in which energy is evolved after completion of reaction or during reaction in the form of heat and energy. They also require energy to initiate a reaction but the amount of energy released is greater than the amount of energy used to start a reaction.
Endothermic reactions: They are defined as the reaction in which energy is used to start a reaction and on completion on reaction they do not evolve energy. If they evolve then the amount of energy evolved is very less than that the amount of energy consumed to start a reaction.
Combustion is an example of exothermic reaction.

Note: We know that oxygen is essential for burning. For example: If you want to burn magnesium oxide then if it does not provide oxygen (air) to the system then it will not burn. Hence magnesium oxide will only burn when you provide oxygen for the reaction.