What chemical is added to pools to increase oxidation?

The correct choice is calcium hypochlorite, which is commonly used in pool maintenance to increase oxidation. This compound acts as a powerful disinfectant and oxidizer, helping to break down organic contaminants in the water, such as bacteria, algae, and debris. By enhancing oxidation, calcium hypochlorite effectively helps to maintain water clarity and sanitation.

Calcium hypochlorite contains a higher available chlorine content than some other forms of chlorine, making it particularly effective at keeping pool water safe and clean. It is typically available in granular form and can be added directly to the pool water, promoting a rapid increase in free available chlorine levels.

The other options, while they also play roles in pool maintenance, do not specifically increase oxidation in the same way. For example, chlorine gas and sodium hypochlorite are both sources of chlorine that provide disinfection; however, they may not be as effective in certain conditions as calcium hypochlorite when it comes to oxidizing pollutants. Magnesium sulfate is primarily used in pools to improve water softness and does not serve the purpose of oxidation.