Question

Assertion (A): $H_{2}S$ acts only as reducing agent.

Reason (R): $H_{2}S$ is a dibasic acid.

• A. Both Assertion and Reason are true and Reason is the correct explanation of Assertion
• B. Both Assertion and Reason are true and Reason is not the correct explanation of Assertion
• C. Assertion is true but Reason is false
• D. Assertion is false but Reason is true

Answer 1

The correct option is

A

Both Assertion and Reason are true and Reason is not the correct explanation of Assertion

$H_{2}S$ acts only as a reducing agent :

This statement is true and the correct explanation is because sulphur here has the least oxidation number in $H_{2}S$ i.e. $-2$. Therefore, it can only lose electrons. Therefore, it acts only as an oxidising agent.

$H_{2}S$ is a dibasic acid :

Basicity of an acid is defined as the power of an acid to neutralize a base. The basicity of an acid depends upon the number of protons donated by an acid to neutralize the base.

The acidity of a base is defined as the power of a base to neutralize an acid. The acidity of a base depends upon the number of protons accepted by the base to neutralize the acid.

Hydrogen sulphide has two hydrogen atoms that can be donated to neutralize the bases. So, hydrogen sulphide will neutralize two base molecules.

Dibasic acid means that the acid can donate two protons to neutralize two base molecules, so hydrogen sulphide is dibasic acid.
$H_{2}S\rightleftharpoons 2H^{+}+S^{2-}$

Hence, this statement is true but not the correct reason for the assertion.

Hence, both Assertion and Reason are true but the Reason is not the correct explanation of Assertion.