Question

Which of the following substances is not combustible?

• A. Lead
• B. Petrol
• C. Sodium
• D. Paper

Answer 1

The correct option is A

Lead

Explanation for the correct option:

A) Lead

• Lead is a non-combustible substance.
• The substances that do not catch fire in the presence of air or oxygen are called non-combustible substances.
• The finely divided lead powder is flammable and gives off irritating or toxic gases in a fire.
• Some other examples of non-combustible substances are carbon dioxide, stone, glass as well as water.

Explanation for the correct options:

B) Petrol

• Petrol is a combustible substance.
• Combustible substances are substances that burn quickly or catch fire quickly.
• At temperatures as low as $-43°\mathrm{C}$, the weak intermolecular interactions between the molecules of petrol allow the molecules to gather enough heat energy to leave as gas and create a combustible mixture with air. In the presence of an ignition source, this flammable mixture will catch fire.

C) Paper

• Paper is a combustible substance.
• Paper is combustible because it is formed from wood pulp, an organic substance that burns when air is present.

D) Sodium

• Sodium is a combustible substance
• Sodium reacts vigorously with air and water. It is an exothermic reaction that generates a lot of heat like fire. As a result hydrogen gas is evolved and sodium hydroxide is formed. Since hydrogen is extremely combustible, it immediately catches fire.

Hence. option (A) is correct. Lead is a non-combustible substance.