Texas Wastewater Class B Practice Exam

When chlorine is added to water, what acids are formed?

1. Hydrochlorous and Sulfuric

2. Hydrochlorous and Acetic

3. Hydrochlorous and Hydrochloric

4. Hydrochloric and Lactic

The correct answer is: Hydrochlorous and Hydrochloric

When chlorine is added to water, it reacts to form hydrochlorous acid and hydrochloric acid. The key reaction involves chlorine dissolving in water, leading to the dissociation of hypochlorous acid (which is formed) into hydrochlorous acid. Hydrochloric acid is also generated in this process. Hydrochlorous acid, although it may not be directly identified in the answer choices, is essentially the active form that contributes to the disinfection properties in water treatment. The context of the other choices indicates that they include acids not typically formed directly from the reaction of chlorine with water. For instance, sulfuric acid and lactic acid are formed through different chemical processes and not as a direct result of chlorine addition to water. Acetic acid is also not a product of chlorine addition and is mainly associated with the fermentation of carbohydrates. Thus, the presence of hydrochloric acid and hydrochlorous acid makes the correct choice an accurate representation of what occurs when chlorine is added to water.