Environmental Engineering Multiple Choice Questions on “Iodine, Bromine and Ozone Treatment”.
1. The chemical formula of hypoiodous acid is __________
a) H2IO
b) H2I
c) HIO
d) HI2
Answer: c
Clarification: The chemical formula of hypoiodous acid is HIO which is formed by the reaction of iodine with water and its chemical equation is I2 + H2O <=> HIO + H+ + I+.
2. At what pH, the dissociation of hypoiodous acid takes place?
a) 1
b) 2
c) 3
d) 4
Answer: d
Clarification: The dissociation of hypoiodous acid takes place at pH = 4.
HIO <=> H+ + IO–.
3. What happens to the hypoiodous acid when the pH is over 8?
a) HIO is stable
b) Formation of hypoiodite ion takes place
c) Formation of iodine and hypoiodite ion takes place
d) Formation of iodine and iodate takes place
Answer: d
Clarification: When pH is over 8, then HIO is unstable and will not form hypoiodite ion. The decomposition of hypoiodite ion takes place, resulting in the formation of iodine and iodate.
4. The chemical formula of iodate is __________
a) HIO3
b) HIO
c) HIO2
d) H2IO2
Answer: a
Clarification: The chemical formula of iodate is HIO3 which is formed when the pH during the decomposition of hypoiodite ion is over 8.
5. a HIO + b OH- <=> HIO3 + b H2O + b I–. What are the values of a and b respectively in the above equation?
a) 1, 2
b) 1, 3
c) 3, 2
d) 3, 1
Answer: c
Clarification: 3HIO + 2OH– <=> HIO3 + 2 H2O + 2 I–. This equation is formed when the pH is above 8 and where decomposition of hypoiodite ion takes place.
6. What happen to the concentration of iodine when the pH is between 6 and 8?
a) I2 decreases whereas HIO increases
b) I2 increases, whereas HIO decreases
c) Both I2 and HIO increases
d) Both I2 and HIO decreases
Answer: a
Clarification: 3HIO + 2OH– HIO3 + 2 H2O + 2 I–. When the pH is between 6 and 8, the percentage of iodine as I2 decreases while the percentage of iodine as HIO is increased.
7. Iodine is a better disinfectant to kill virus than hypoiodous acid.
a) True
b) False
Answer: b
Clarification: Hypoiodous acid destroys viruses at a considerably faster rate than I2 as iodine has little viricidal activity.
8. Ozone is a _______ allotrope of oxygen.
a) Monoatomic
b) Diatomic
c) Triatomic
d) Polyatomic
Answer: c
Clarification: Ozone is a triatomic allotrope of oxygen, which is an unstable gas and the breakdown into normal oxygen containing two atoms of oxygen by molecule.
9. The ozone generators can convert ____ % of feed oxygen into ozone.
a) 1
b) 5
c) 1-4
d) 10
Answer: c
Clarification: The ozone generators can convert 1-4 % of feed oxygen into ozone. They are used as an effective method to clean indoor air pollution and odors.
10. What happens during the breakdown of ozone?
a) CO2 is formed
b) Nascent oxygen is formed
c) CO2 and Nascent oxygen is formed
d) Formation of oxygen and water takes place.
Answer: b
Clarification: During the breakdown of ozone, nascent oxygen is formed which contains a single atom of oxygen.
11. Which of the following is most effective in the killing of bacteria present in water?
a) Nascent oxygen
b) Chlorine
c) HOBr
d) I2
Answer: a
Clarification: Nascent oxygen is very effective in oxidizing the organic matter and in the killing of bacteria present in the water which is formed during the breakdown of ozone.
12. The water is free from oxidizable materials. What is the dosage of ozone required?
a) 0.01ppm
b) 0.1-0.2ppm
c) 0.2-0.3ppm
d) 0.4-0.5ppm
Answer: c
Clarification: A dosage of 0.2-0.3ppm is required to kill the coliform bacteria present in water which is free from oxidizable materials.
13. The dosage of ozone for municipal water treatment is __________
a) 0.5 ppm
b) 1ppm
c) 1.5 ppm
d) 2ppm
Answer: c
Clarification: The dosage of ozone for municipal water treatment is 1.5ppm, which is not only used for disinfection but also it removes taste, color and odor from water.