Florida Drinking Water Operator "B" Practice Test

A dosage of 3 parts chlorine to 1 part ammonia forms which compound?

1. Chloroform

2. Monochloramine

3. Dichloramine

4. Ammonia chlorine

The correct answer is: Monochloramine

A dosage of 3 parts chlorine to 1 part ammonia forms monochloramine, which is a chloramine compound. When chlorine is added to ammonia, it can react in various proportions to form different chloramine species. In the case of a 3:1 ratio of chlorine to ammonia, the chlorine reacts with ammonia to create monochloramine, which is a stable compound used in water treatment for disinfection and maintaining residuals. Monochloramine is favored in many water treatment processes because it provides a longer-lasting disinfectant residual than free chlorine and produces fewer disinfection byproducts. The formation of other chloramine species, such as dichloramine or nitrogen trichloride, requires different ratios of chlorine to ammonia. Dichloramine typically forms when there is a higher concentration of chlorine relative to ammonia, while nitrogen trichloride forms when ammonia is significantly outnumbered by chlorine. Thus, the specific ratio of chloramines formed is critical in determining the resulting compound, making the identification of monochloramine in the 3:1 ratio correct.