An increase in equivalent conductance of a strong electrolyte with dilute dilution is mainly due to:

Increase in ionic mobility of ions

The correct answer is option 2. Increase in ionic mobility of ions.

An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to increase in ionic mobility of ions

When a strong electrolyte is diluted, the number of ions in the solution increases due to dissociation, which contributes to the increase in conductivity. However, the main factor responsible for the increase in conductivity per unit concentration (equivalent conductance) is the increase in the mobility of ions. As the solution becomes more dilute, the ions experience less interference from each other and from solvent molecules, allowing them to move more freely through the solution, thus increasing the conductivity. Therefore, option (b) Increase in ionic mobility of ions is the correct explanation.