Assertion:  Equivalent weight of  HCl is always 36.5. 
Reason:  Equivalent weight of HCl can be zero

The equivalent weight of a substance is the weight of the substance that reacts with or supplies 1 mole of hydrogen ions (H⁺) or hydroxide ions (OH^-) during a reaction. It is calculated using the formula:

Equivalent weight = Molar mass / n-factor

Where:

• Molar mass of HCl is 36.5 g/mol.
• n-factor depends on the reaction, which, in the case of HCl, is typically 1 (as HCl donates one H⁺ ion).

Analysis of the Assertion and Reason

1. Equivalent Weight of HCl:

The molar mass of HCl is 36.5 g/mol, and since it donates one H⁺ ion, its equivalent weight is:

Equivalent weight = 36.5 / 1 = 36.5

Hence, the equivalent weight of HCl is generally 36.5.

2. Can Equivalent Weight Be Zero?

No, equivalent weight cannot be zero. The formula for equivalent weight involves division by the n-factor. While the n-factor might vary depending on the chemical reaction, it cannot be zero because it represents the number of ions or electrons exchanged in a reaction.

A zero n-factor would imply no reaction occurred, which is not meaningful in this context.

3. Exception:

In some rare chemical reactions, the effective n-factor of HCl might change, making its equivalent weight different from 36.5. For instance, in reactions involving multiple HCl molecules co cntributing to the reaction, the equivalent weight can appear to be higher than 36.5. However, it cannot be zero.

Correct Explanation of the Statement

• Assertion: Correct. The equivalent weight of HCl is generally 36.5.
• Reason: Incorrect. The equivalent weight of HCl cannot be zero, as this contradicts the definition of equivalent weight.

Correct Explanation:

The equivalent weight of HCl is mainly 36.5 because its n-factor is 1 in most cases. In some exceptions, where the n-factor changes due to specific reaction conditions, the equivalent weight might exceed 36.5. However, it is impossible for the equivalent weight to be zero, as this would imply no participation in the reaction, which is invalid.