Correct Option (A)
In a dry cell, such as the Leclanché cell, the electrolyte is present in a paste form rather than a liquid. Ammonium chloride (NH₄Cl) is traditionally used as the primary electrolyte, facilitating the ionic conduction necessary for the cell's operation. In modern zinc-carbon dry cells, zinc chloride (ZnCl₂) is often incorporated, either partially or completely replacing ammonium chloride. Zinc chloride helps to improve the cell's performance and extend its shelf life by reducing the rate of side reactions and maintaining a more stable pH. Both compounds function as electrolytes, enabling the movement of ions required for current generation.
Incorrect Options:
Sodium chloride (NaCl) is common table salt and is not utilized as an electrolyte in dry cells. Calcium chloride (CaCl₂) is primarily known for its use as a desiccant (drying agent) and in de-icing applications, not as a component of dry cell electrolytes.
While zinc chloride (ZnCl₂) is a valid electrolyte in modern dry cells, magnesium chloride (MgCl₂) is not used for this purpose. Magnesium chloride finds applications in areas such as fireproofing agents and the production of magnesium metal.
Although ammonium chloride (NH₄Cl) is a correct electrolyte for dry cells, calcium chloride (CaCl₂) is not. Calcium chloride does not possess the chemical properties or fulfill the functional requirements for an electrolyte in dry cell chemistry.