What substance dissolves manganese and calcium carbonate in the filtration process?

The correct answer is sulfur dioxide. This substance is commonly used in water treatment applications to remove manganese and calcium carbonate from water during the filtration process. Sulfur dioxide acts as a reducing agent, which can effectively react with manganese, converting it to a soluble form. In the case of calcium carbonate, sulfur dioxide helps reduce the pH of the water, which increases the solubility of calcium and carbonate ions. As a result, these compounds can be more readily filtered from the water, improving its quality.

In contrast, the other options do not have the same effect on manganese and calcium carbonate. Hydrogen peroxide is primarily an oxidizer and not effective in dissolving these specific compounds in this context. Calcium carbonate itself cannot dissolve calcium carbonate, as it is the substance in question. Chlorine gas, while used for disinfection, does not effectively dissolve these compounds and is more focused on killing pathogens in water rather than addressing mineral deposits.