Chemistry Multiple Choice Questions on “Environmental Chemistry – Water Pollution”.
1. What is an easily identified source of pollution called as?
a) Specific source
b) Point source
c) Non-point source
d) Polluting source
Answer: b
Clarification: Easily identified source or place of pollution is called as point source. The examples of point sources are municipal and industrial discharge pipes where the pollutants enter the water-source as treated wastewater. A point source has a negligible extent, distinguishing it from other pollution source geometries.
2. Pick out the source of organic wastes pollutant from the following.
a) Industries
b) Erosion of soil by agriculture and strip mining
c) Water used for cooling in factories
d) Discharge from food processing factories
Answer: d
Clarification: Organic wastes, also known as biodegradable wastes, are natural wastes of plants and animals. The source of organic wastes include domestic sewage, animal excreta and waste, decaying animals and plants, as well as discharge from food processing factories. They can ultimately lead to harm when they use up the oxygen in the water body that they are dumped into.
3. Identify the bacteria not found in human excreta that causes gastrointestinal diseases.
a) Staphylococcus aureus
b) Escherichia coli
c) Streptococcus faecalis
d) Shigella
Answer: a
Clarification: Staphylococcus aureus is not found in human excreta. It is a round-shaped bacterium that is a member of the Firmicutes. It is mainly found on the upper respiratory tract and/or on skin. But they can also spread through the bloodstream and infect distant organs. Infections caused due to this bacterium can be transferred through the air, skin contact, etc.
4. Plants always take in carbon dioxide and release oxygen.
a) True
b) False
Answer: b
Clarification: Plants do not always take in carbon dioxide and release oxygen. Plants take in carbon dioxide during the day for the process of photosynthesis and release oxygen into the atmosphere. But at night, photosynthesis does not occur, due to the absence of sunlight, and therefore plants take in oxygen for breathing and give out carbon dioxide.
5. What is the amount of oxygen required by bacteria to break down organic matter present in certain volume of sample of water is called?
a) Bacterial oxidation
b) Bacterial decomposition
c) Biochemical oxygen demand
d) Biological oxygen demand
Answer: c
Clarification: The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water is called as Biochemical Oxygen Demand (BOD). The amount of BOD in water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water has BOD value less than 5 ppm whereas highly polluted water has BOD value of 17 ppm or more.
6. What does the addition of phosphate fertilizers into water lead to?
a) Increased algae growth
b) Decreased algae growth
c) Increased growth of decomposers
d) Nutrient enrichment
Answer: d
Clarification: Addition of phosphate fertilizers into water bodies lead to nutrient enrichment. This condition is also known as eutrophication. When excess nutrients are formed, this, in turn, will lead to the growth of algae in the water body. These algae will consume the oxygen that is present in the water and thus, there will not be sufficient oxygen left for use of the aquatic organisms inhabiting the water body. As a result, death of these aquatic organisms will take place in large quantities. And therefore, leads to pollution.
7. What is the full form of PCB(in the context of chemistry)?
a) Printed Circuit Boards
b) Polychlorinated biphenyls
c) Polychemical biphenyls
d) Primary Chemical Bacteria
Answer: b
Clarification: The full form of PCB is Polychlorinated biphenyls. It is used as a cleansing solvent. PCBs are also suspected to be carcinogenic (can lead to cancer). Bacteria responsible for degrading biodegradable detergent feed on these and grow rapidly. While growing, they use up all the oxygen dissolved in water. Thus, the lack of oxygen kills all other forms of aquatic life such as fish and plants.
8. Water should be tested for fluoride ion concentration for drinking purposes.
a) True
b) False
Answer: a
Clarification: For drinking purposes, water should be tested for fluoride ion concentrations. Its deficiency in drinking water is harmful to man and causes diseases such as tooth decay. But, if present in higher concentrations, it causes brown mottling of teeth. It can also lead to harmful effects in bones.
9. The maximum limit of which of the following in drinking water should be 50 ppb?
a) Lead
b) Sulphate
c) Nitrate
d) Fluoride
Answer: a
Clarification: The maximum prescribed upper limit concentration of lead in drinking water is about 50 ppb. Drinking water gets contaminated with lead when lead pipes are used for the transportation of drinking water. Lead is a harmful substance and can cause damage in kidneys, liver, reproductive system, etc.
10. The excess of which ion in drinking water can lead to blue baby syndrome?
a) Aluminum ion
b) Copper ion
c) Sulphate ion
d) Nitrate ion
Answer: d
Clarification: Blue baby syndrome (methemoglobinemia) is a disease that is caused when the baby consumes drinking water which is rich in nitrates. It is caused when the maximum limit of nitrate in water, i.e. 50ppm, is crossed. When the baby drinks nitrate-rich water, then the nitrates get converted to nitrites and this will go and bind with the haemoglobin present in the blood, forming methemoglobin, which does not have the ability to carry oxygen. This is the reason for the blue color of the skin of the baby.