BOD and COD

Q. In highly polluted water BOD value shows a range of

1. 17-50 ppm

2. 10-14 ppm

3. 7-12 ppm

4. 2-8 ppm

Q. Which of the following statement is false?

1. The main reason for river water pollution is industrial and domestic sewage discharge.
2. Oil slick in sea water increases D.O. value.
3. Surface water contains a lot of organic matter, mineral nutrients and radioacative material
4. Oil spill in sea water causes heavy damage to fishery

Q. If BOD of river is high, it means that the river is:

1. Not polluted
2. Very much polluted with inorganic chemicals
3. Polluted with pesticides
4. Very much polluted with organic chemicals which are decomposed by micro-organisms

Q. If BOD of river is high, it means that:

1. The river is not polluted
2. The river is very polluted
3. The river gets less light
4. The temperature is low

Q. Biochemical oxygen demand (BOD), is a measure of organic material present in water. A BOD value less than 5 ppm indicates the water sample to be:

1. Highly polluted
2. Rich in dissolved oxygen
3. Poor in dissolved oxygen
4. Not suitable for aquatic life

Q. Biochemical Oxygen Demand, (BOD) is a measure of organic material present in water. BOD of less than 5 ppm indicates a water sample to be:

1. Rich in dissolved oxygen
2. Poor in dissolved oxygen
3. Highly polluted
4. Not suitable for aquatic life

Q. 100 mL of a water sample contains 0.81 g of calcium bicarbonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of $CaC{O}_3$ is:
(molar mass of calcium bicarbonate is $162gmo{l}^{-1}$ and magnesium bicarbonate is $146gmo{l}^{-1}$)

1. 1000 ppm
2. 5000 ppm
3. 100 ppm
4. 10000 ppm

Q. The value of biological oxygen demand of highly polluted water is:

1. < 5 ppm
2. = 5 ppm
3. = 16 ppm
4. > 16 ppm

Q. Assertion
If BOD level of water in reservoir is less than 5 ppm it is not polluted.

Reason
High biological oxygen demand means low activity of bacteria in water.

1. Assertion is correct but Reason is incorrect
2. Both Assertion and Reason are incorrect
3. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
4. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Q. Which of the following is a measurement of water polluiton?

1. PSC
2. PCB
3. COD
4. BOD