Which type of chlorine compound is known to be the most powerful?

The most powerful chlorine compound among the options is chlorine gas. Chlorine gas is highly reactive and has a strong oxidizing potential, making it effective for disinfection and water treatment. It can kill bacteria, viruses, and other pathogens very efficiently, thereby being considered a powerful biocide.

While sodium hypochlorite and calcium hypochlorite are also strong disinfectants, they are less potent compared to chlorine gas because they rely on a reaction to release chlorine, which is the active disinfectant in both compounds. Potassium permanganate, although a strong oxidizer, is not a chlorine compound and functions differently in water treatment processes.

Therefore, chlorine gas is recognized as the most powerful among the stated options, due to its immediate oxidizing properties and effectiveness in controlling pathogens.