Which type of chlorine is known as unbound?

The type of chlorine known as unbound is indeed free chlorine. Free chlorine refers to the chlorine that is present in its elemental form and is available to react with pathogens in water. It includes both chlorine gas (Cl2) and hypochlorous acid (HOCl), which are effective disinfectants.

Free chlorine is important in water treatment processes because it can actively kill bacteria and viruses, helping to ensure that the water is safe for consumption. This is in contrast to combined chlorine, which forms when free chlorine reacts with ammonia or nitrogenous compounds in the water, producing chloramines. These chloramines can be less effective as disinfectants.

Other types of chlorine, such as organic chlorine, refer to chlorine that is bonded to organic compounds and does not exist as free or unbound chlorine, while residual chlorine typically refers to the concentration of chlorine that remains in the water after treatment, which may include both free and combined forms. Therefore, identifying free chlorine as unbound correctly highlights its role and effectiveness in water disinfection.