Tennessee Wastewater Operator Practice Exam

Chlorine and hypochlorite break down water to form which of the following?

1. Hydrochloric acid and chlorine gas

2. Hypochlorite acid and hypochlorite ion

3. Chlorine dioxide and hypobromous acid

4. None of the above

The correct answer is: Hypochlorite acid and hypochlorite ion

The correct answer is the formation of hypochlorite acid and hypochlorite ion when chlorine and hypochlorite are involved in a reaction in water. In the context of water treatment, chlorine (Cl2) and hypochlorite (OCl-) are commonly used as disinfectants. When chlorine is dissolved in water, it can form hypochlorous acid (HOCl), which is a potent disinfectant. The hypochlorous acid can then dissociate into hypochlorite ions in a pH-dependent manner. At higher pH levels, hypochlorous acid predominates and can dissociate into hypochlorite ions. This process is crucial for understanding the chlorination process in wastewater treatment, as both forms play a significant role in disinfection and maintaining water quality. The presence of hypochlorite ions has important implications for reducing pathogen levels in the treated wastewater. In contrast, other options do not accurately reflect the chemistry involved with chlorine and hypochlorite in the context of their interaction with water. The emphasis on hypochlorite, both in its acid form and ion form, is key to the understanding of chlorine-based disinfection processes.