Which among the following chemicals is used to purify water as a disinfectant?

Chlorine 

The correct answer is option 1. Chlorine.

The chemical used to purify water as a disinfectant is Chlorine. Chlorine is commonly used to disinfect water and kill bacteria, viruses, and other pathogens. It is added to water treatment systems in the form of chlorine gas, sodium hypochlorite (liquid bleach), or calcium hypochlorite (solid form). Chlorine effectively destroys harmful microorganisms, making water safe for consumption.