Question

Which of the following non-metals reacts and catches fire on exposure to air?

• A. Phosphorus
• B. Nitrogen
• C. Sulphur
• D. Hydrogen

Answer 1

The correct option is A

Phosphorus

Explanation of the correct option:

(A) Phosphorous

• Phosphorous is a non-metal which is very reactive and it can spontaneously react with oxygen and catches fire.
• Because of this reason, phosphorous is stored underwater to avoid burning in the presence of air.
• White phosphorous is more reactive than red phosphorous.

${\mathrm{P}}_4\left(\mathrm{s}\right)+5{\mathrm{O}}_2\left(\mathrm{g}\right)\to 2{\mathrm{P}}_2{\mathrm{O}}_5\left(\mathrm{s}\right)$

Explanation of the incorrect options:

(B) Nitrogen

• Nitrogen doesn't react with oxygen at normal temperature but at high-temperature nitrogen reacts with oxygen and forms nitric oxide.

(C) Sulphur

• When sulphur reacts with oxygen it forms sulphur dioxide and does not catch fire.

(D) Hydrogen

• When hydrogen reacts with oxygen it forms either water or hydrogen peroxide.

Hence, option (A) is correct. Phosphorous reacts and catches fire on exposure to air.