MCQ Questions for Class 11 Chemistry Chapter 14 Environmental Chemistry with Answers

Answer: (c) Cotton field
Explanation:
Rice is grown in flooded fields, a situation that depletes the soil of oxygen. Soils that are anaerobic (lacking oxygen) allow the bacteria that produce methane from decomposing organic matter to thrive. Some of this methane then bubbles to the surface, but most of it is diffused back into the atmosphere through the rice plants themselves. Hence, rice Paddy field that produces maximum methane gas into the atmosphere.

Answer: (b) Fluorides in water
Explanation:
Skeletal fluorosis is a bone disease caused by excessive accumulation of fluoride in the bones. In advanced cases, skeletal fluorosis causes painful damage to bones and joints.

Answer: (d) CO.
Explanation:
Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities. Transportation contributes to more than half of the carbon monoxide, sulphur dioxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into our air. Carbon monoxide (CO) is a colourless, odourless, toxic non-irritating gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.

Answer: (d) Freons.
Explanation:
Fluorocarbons such as freon-1 (CFCl₃) and freon-12 (CF₂Cl₂) emitted as propellants in aerosol spray cans, refrigerators, fire fighting reagents etc. are stable compounds and chemically inert. They do not react with any substance with which they come in contact and thus float through the atmosphere unchanged and eventually enter the stratosphere. There they absorb UV radiations and break down liberating free atomic chlorine which causes decomposition of ozone. This results in the depletion of the ozone layer.

Answer: (c) Soil
Explanation:
Photochemical smog is produced when pollutants from the combustion of fossil fuels react with sunlight. The energy in the sunlight converts the pollutants into other toxic chemicals. For photochemical smog to form, there must be other pollutants in the air, specifically nitrous oxides and other volatile organic compounds (VOCs).

Answer: (c) Microorganisms present in the soil
Explanation:
CO is converted into CO₂ by microorganism present in soil.

Answer: (b) Biodegradable pollution
Explanation:
Domestic waste mostly constitutes biodegradable pollution.

Answer: (d) Nuclear Fallout.
Explanation:
Nuclear fallout, or simply fallout, is the residual radioactive material propelled into the upper atmosphere following a nuclear blast or a nuclear reaction conducted in an unshielded facility, so called because it “falls out” of the sky after the explosion and the shock wave have passed. While deforestation, soil erosion and increasing deserts can be controlled, nuclear fallout causes genetic mutation in humans and destruction that cannot be controlled or cured.

Answer: (c) Thermal power stations
Explanation:
Thermal power plant, agro industry and mining all are responsible for soil and water pollution. (Due to extraction of chemicals which cause pollution)

Answer: (c) Amount of BOD
Explanation:
The amount of oxygen required to break down a certain amount of organic matter is called the biological oxygen demand (BOD). The amount of BOD in water is an indicator of the level of pollution.

Answer: (c) Microorganisms present in the soil
Explanation:
CO is converted into CO₂ by microorganism present in soil.

Answer: (d) Ammonia acts as a sink for NO_x.
Explanation:
The average residence time of NO is 4 days.

Answer: (a) Minamata disease
Explanation:
Disease caused by eating fish found in water contaminated with industrial waste having mercury is minamata disease.

Answer: (d) Freons.
Explanation:
Fluorocarbons such as freon-1 (CFCl₃) and freon-12 (CF₂Cl₂) emitted as propellants in aerosol spray cans, refrigerators, fire fighting reagents etc. are stable compounds and chemically inert. They do not react with any substance with which they come in contact and thus float through the atmosphere unchanged and eventually enter the stratosphere. There they absorb UV radiations and break down liberating free atomic chlorine which causes decomposition of ozone. This results in the depletion of the ozone layer.

Answer: (c) Soil
Explanation:
Photochemical smog is produced when pollutants from the combustion of fossil fuels react with sunlight. The energy in the sunlight converts the pollutants into other toxic chemicals. For photochemical smog to form, there must be other pollutants in the air, specifically nitrous oxides and other volatile organic compounds (VOCs).

Answer: (d) Ozone layer does not permit infrared radiation from the sun to reach the earth.
Explanation:
Allotropes of Oxygen-
O₂ (Dioxygen) and O₃ (Ozone)
Infrared radiation is most important for heating up the atmosphere and the surface of the earth. These rays have high wavelength and low frequency and are not very harmful. Ozone does not hinder infrared radiation.

Answer: (b) CH₂ = CH₂

Answer: (c) O₃
Explanation:
Ultraviolet radiations cause photochemical splitting of oxygen molecules in the stratosphere. The nascent oxygen combines with molecular oxygen to form ozone. In troposphere nascent oxygen comes from nitrogen dioxide.

Answer: (b) Due to run-off excess fertilizers
Explanation:
Inorganic plant nutrients found in fertilizers. Run-off carries excess fertilizers into nearby water bodies, causing high levels of plant nutrients which promote the excessive growth of algae and other aquatic plants.

Answer: (b) CO
Explanation:
Important Air pollutants
Oxides of carbon (CO,CO₂)
Oxides of sulphur (SO₂ & SO₃)
Oxides of nitrogen
Chlorofluoro carbons (CFC)
Hydrocarbons Like CH₄
​Photochemical and Industrial smog.
Dust & other particulate matter from industries.