Questions about chlorine

Certification Action Line features questions and answers typical of those appearing in Water Quality Association (WQA) certification examinations. Some answers may not satisfy everyone or every condition.

1. Chlorine is a member of the ______ family.
a) alkali
b) alkaline earth
c) halogen
d) actinide

2. Chlorine has ___________ uses.
a) diverse
b) limited

3. Chlorine compounds in water form _____.
a) sodium hypochlorite
b) calcium hypochlorite
c) hypochlorous acid
d) hypochlorite ion

4. ________ is a stronger oxidant and has greater biocide efficacy. a) Hypochlorous acid (HOCl) b) Hypochlorite ion (OCl^–)

5. Reactions with ammonia to form chloramines can be overcome by __________.
a) chlorine gas
b) high test chlorine
c) breakpoint chlorination

6. Chlorine demand can be increased by ___________ in water. a) ferrous iron (Fe⁺⁺) b) manganese (Mn⁺⁺) c) sulfides (S⁼) d) humic organic substances e) pollen f) all of the above7. Compared to chlorine, chlorine dioxide (ClO₂) is a ______________ powerful water disinfectant. a) more b) less8. Chlorine dioxide is purchased from a supply house in the form of sodium chlorite (NaClO₂). a) True b) False9. The treatment of natural waters with chlorine dioxide results in these by-product formations. a) chloroform and other trihalomethanes b) chlorite ion (ClO_2-) c) chloramines d) chlorate ion (ClO_3-)

10. High pH _____________ the effectiveness of chlorine dioxide disinfection and oxidation in water.
a) increases
b) decreases
c) does not affect