This set of Class 11 Chemistry Chapter 14 Multiple Choice Questions & Answers (MCQs) focuses on “Environmental Chemistry – Soil Pollution”.
1. Before World War II, which chemical was used for pest control?
c) Boric acid
Explanation: Prior to World War II, many naturally occurring chemicals such as nicotine were used as pest controlling substances for major crops in agricultural practices. This was achieved by planting tobacco plants in the crop fields.
2. Which one of the following chemicals has been banned in India?
Explanation: During World War II, DDT was found to be of great use in the control of malaria and other insect-borne diseases. Therefore, after the war, DDT was put to use in agriculture to control the damages caused by insects, rodents, weeds, and various crop diseases. However, due to adverse effects, its use has been banned in India.
3. Pick out the correct characteristic of organic toxins.
a) insoluble, non-biodegradable
b) soluble, non-biodegradable
c) insoluble, biodegradable
d) soluble, biodegradable
Explanation: Organic toxins are poisonous substances derived from living organisms. Most of the organic toxins are water insoluble and non-biodegradable. These high persistent toxins are, therefore, transferred from lower trophic level to higher trophic level through food chain. Organic toxins are almost equally harmful as the synthetic chemicals to humans.
4. At each trophic level, the pollutant gets 10 times more concentrated.
Explanation: As we go up the food chain, the concentration of pollutant increases. This process is called biomagnification. This process refers to the buildup of toxins in the food chain. At each trophic level, the pollutant gets 10 times more concentrated. Therefore, the animals near the top of the food chain gets the most affected by the toxins.
5. Identify the substance that is not an organic toxin.
c) Hydrogen sulphide
Explanation: Hydrogen sulphide is not an organic toxin. It is an inorganic toxin. It exists in the gas phase at ambient temperatures, if finely divided or has a high vapor pressure. But, hydrogen sulphide, becomes far less toxic, when oxidized. Aldrin, Dieldrin, and Toxaphene are organic toxins.
6. Pick out the correct statement about carbamates from the following.
a) They are less harmful to human life
b) They offer excellent insect-resistance
c) They are less persistent
d) They are non-biodegradable
Explanation: Carbamates are less persistent and more biodegradable products. They were introduced in response to high persistence of chlorinated organic toxins. But these chemicals are severe nerve toxins and hence more harmful to humans. Insects have become resistant to these insecticides also.
7. Identify the correct statement regarding negative soil pollution.
a) Contamination of the soil due to addition of insecticides
b) Reduction in soil productivity due to soil erosion
c) Reduction in soil productivity due to the addition of pesticides and herbicides
d) Contamination of the soil due to natural disasters.
Explanation: Negative soil pollution is caused due to the overuse of soil and also due to soil erosion, and thereby, leading to decrease in soil productivity and efficiency. The other factors that can contribute to negative soil erosion are developmental activities, overgrazing, etc.
8. Pesticides and herbicides are the major components of chemical pollution.
Explanation: Pesticides and herbicides represent only a very small portion of the widespread chemical pollution. A large number of other compounds that are used regularly in chemical and industrial processes for manufacturing activities are finally released into the atmosphere in one or another form.
9. In the recent days, where has the pesticide industry has shifted to?
a) Stronger pesticides
Explanation: These days, the pesticide industry has shifted its attention to herbicides. During the first half of the last century, this shift from mechanical to chemical weed control had provided the industry with flourishing economic market.
10. Which of the following is an herbicide?
c) Sodium chloride
d) Sodium arsinite
Explanation: Sodium arsinite is an herbicide. It is less persistent but toxic to mammals. It decomposes in a few months. Like organo-chemicals, this will also get concentrated in the food web. Some herbicides can also cause birth defects. Other examples of herbicides include diclofop, sodium chlorate, etc.
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