NEET-XI-Chemistry
07: Environmental Chemistry
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- Qstn #15What are pesticides and herbicides? Explain giving examples.
Ans : Pesticides are a mixture of two or more substances. They are used for killing pests. Pests include insects, plant pathogens, weeds, mollusks, etc., that destroy the plant crop and spread diseases. Aldrin and dieldrin are the names of some common pesticides
Herbicides are pesticides specially meant for killing weeds. For example, sodium chlorate (NAClO3), sodium arsenite (Na3AsO3), etc.
- Qstn #16What do you mean by green chemistry? How will it help decrease environmental pollution?
Ans : Green chemistry is a production process that aims at using the existing knowledge and principles of chemistry for developing and implementing chemical products and processes to reduce the use and generation of substances hazardous to the environment
The release of different harmful chemicals (particulates, gases, organic and inorganic wastes) causes environmental pollution. In green chemistry, the reactants to be used in chemical reactions are chosen in such a way that the yield of the end products is up to 100%. This prevents or limits chemical pollutants from being introduced into the environment. Through the efforts of green chemists, H2O2 has replaced tetrachlorethane and chlorine gas in drying and bleaching of paper.
- Qstn #17What would have happened if the greenhouse gases were totally missing in the earth’s atmosphere? Discuss.
Ans : Earth’s most abundant greenhouse gases are CO2, CH4, O3, CFCs, and water vapour. These gases are present near the Earth’s surface. They absorb solar energy that is radiated back from the surface of the Earth. The absorption of radiation results in the heating up of the atmosphere. Hence, greenhouse gases are essential for maintaining the temperature of the Earth for the sustenance of life.
In the absence of greenhouse gases, the average temperature of the Earth will decrease drastically, making it uninhabitable. As a result, life on Earth would be impossible.
- Qstn #18A 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.
Ans : The amount of dissolved oxygen present in water is limited. The abundance of phytoplanktons causes depletion of this dissolved oxygen. This is because, phytoplanktons are degraded by bacteria present in water. For their decomposition, they require a large amount of oxygen. Hence, they consume the oxygen dissolved in water. As a result, the BOD level of water drops below 6 ppm, inhibiting the growth of fish and causing excessive fish-kill.
- Qstn #19How can domestic waste be used as manure?
Ans : Depending upon the nature of the waste, domestic waste can be segregated into two categories i.e., biodegradable and non-biodegradable. Biodegradable waste such as leaves, rotten food, etc. should be deposited in land fills, where they get decomposed aerobically and anaerobically into manure. Non-biodegradable waste (which cannot be degraded) such as plastic, glass, metal scraps etc. should be sent for recycling.
- Qstn #20For your agricultural field or garden you have developed a compost producing pit. Discuss the process in the light of bad odour, flies and recycling of wastes for a good produce.
Ans : It is essential to take proper care of the compost producing pit in order to protect ourselves from bad odour and flies.
It should be kept covered to minimize bad odour and prevent flies from entering it.
The recyclable waste should not be dumped in the compost producing pit. It should be sent to the industries through vendors for recycling.