Calcium hypochlorite is produced by reacting chlorine with what?

Calcium hypochlorite is produced by reacting chlorine with lime, which is chemically known as calcium hydroxide. When chlorine gas is introduced to hydrated lime, a chemical reaction occurs that results in the formation of calcium hypochlorite along with water. This compound is widely used in the water treatment industry as a disinfectant and bleaching agent due to its strong oxidizing properties.

The reaction can be represented as follows:

[ \text{Cl}_2 + \text{Ca(OH)}_2 \rightarrow \text{Ca(OCl)}_2 + \text{H}_2\text{O} ]

This process is important in water disinfecting operations because calcium hypochlorite is effective in killing bacteria and other pathogens in water, ensuring safe drinking water and preventing waterborne diseases.

The other options do not lead to the formation of calcium hypochlorite through a direct chemical reaction with chlorine. Water, sand, and sodium do not produce calcium hypochlorite in this manner, which solidifies lime's role as the essential reactant in the production of this important water treatment chemical.