BOD and COD

Q.

BOD stands for

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. 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. 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. 10000 ppm
4. 100 ppm

Q. The concentration of dissolved oxygen (DO) in cold water can go upto :

1. 10 ppm
2. 16 ppm
3. 14 ppm
4. 8 ppm

Q. Which of the following statement(s) is/(are) the incorrect reason for eutrophication?
(A) excess usage of fertilisers

(B) excess usage of detergents

(C) dense plant population in water bodies

(D) lack of nutrients in water bodies that prevent plant growth

Choose the most appropriate answer from the option given below:

1. (D) only
2. (C) only
3. (B) and (D) only
4. (A) only

Q.

A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.

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. In a sample of water (200g) contains 6 × 10^-4 g of dissolved oxygen. Calculate the ppm concentration of oxygen ?

Q.

How is biochemical oxygen demand (BOD) different from chemical oxygen demand (COD)?

Q.

What do you mean by Biochemical Oxygen Demand (BOD)?

Q.

How does BOD differ from COD?

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

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

Q.

The gas originally called ‘fixed air’?

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

1. rich in dissolved oxygen
2. poor in dissolved oxygen
3. highly polluted
4. not suitable for aquatic life

Q. Assertion :The amount of BOD in the waters is a measure of the amount of organic material in the water. Reason: Clear water has BOD less than 5 ppm whereas highly polluted water have BOD value of 17 ppm or more.

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

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

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

Q. Water samples with $BOD$ values of $4ppm$ and $18ppm$, respectively, are:

1. clean and highly polluted
2. highly polluted and highly polluted
3. clean and clean
4. highly polluted and clean

Q. The value of dissolved oxygen in polluted water is:

1. $>4$ ppm
2. $=4$ ppm
3. $=6$ ppm
4. $<4$ ppm

Q. A sample of hard water contains 1 mg of $CaC{l}_2$ and 1 mg $MgC{l}_2$ per litre. Calculate the hardness of water in terms of $CaC{O}_3$ present in per ${10}^6$ parts of water.

Q. Biochemical Oxygen Demand(BOD) value can be a measure of water pollution caused by the organic matter. Which of the following statements is correct?

1. Polluted water has BOD value higher than $10$ ppm
2. Aerobic bacteria decrease the BOD value
3. Clean water has BOD value higher than $10$ ppm
4. Anaerobic bacteria increase the BOD value

Q. $74.5g$ of metal chloride contains $35.5g$ of chlorine. The equivalent weight of metal is:

1. $74.5$
2. $39$
3. $35.5$
4. $7.45$

Q. Biological Oxygen Demand (BOD) can be defined as:

1. the amount of oxygen required by bacteria to break down the organic matter of a sample of water
2. the amount of chemicals required to break down the organic matter of a sample of water
3. the amount of phosphate required to oxidise the organic matter of a sample of water
4. the amount of organic matter present in the given sample of water

Q. Four samples of water A, B, C and D have the DO values 1 mg/litre, 3mg/litre, 5 mg/litre and 8mg/litre respectively. Which one is more polluted sample of water?

1. A
2. B
3. C
4. D

Q. If water is polluted, its BOD (biochemical oxygen demand) value is:

1. < 1 ppm
2. < 2 ppm
3. < 3 ppm
4. > 6 ppm

Q. Pollution of lakes and rivers affects aquatic life. Fish cannot live in water that has oxygen less than $4$ milligrams per liter. Other freshwater aquatic life (including anaerobic bacteria) also cannot survive without adequate oxygen. 'BOD' stands for:

1. Building oxygen deposits
2. Biological oxygen demand
3. Basic oxygen demand
4. Bacterial oxygen deficit

Q. The COD values of three water samples A, B and C are 60 ppm, 990 ppm and 120 ppm respectively. The most polluted water sample is:

1. A
2. All are equally polluted
3. B
4. C

Q. Identify the correct sequence of steps in an experiment to show the effect of temperature on the rate of the reaction.
(a) Measuring the volumes of $H_2$ gas liberated in two test tubes.
(b) Heating the test tube B by ${10}^{\circ }C$.
(c) Comparison of relative volumes of $H_2$ liberated in test tubes B and A.
(d) Addition of same concentration of $HCl$ to the two test tubes.
(e) Taking equal masses of fine granules of zinc in two test tubes A and B.

1. edbac
2. baced
3. cdeab
4. edbca