Free Environmental Chemistry MCQs with Answers

91. Fungicides are the pesticides which:

• A. Kill insects
• B. Kill fungus
• C. Kill plants
• D. Kill herbs

Explanation: The most important and widely used pesticides are insecticides (which kill insects), herbicides (which kill undesired plants) and fungicides (which control the growth of fungus on the plant).

92. The main pollutant of leather tanneries in the waste water is due to the salt of:

• A. Lead
• B. Chromium (III)
• C. Chromium (VI)
• D. Copper

Explanation: Leather tanneries use large quantities of chromium (VI) salts for leather tanning. They are producing good variety of exportable leather, but only some units have the facility of waste water treatment by reducing Cr (VI) into trivalent state followed by alkaline precipitation of Cr (OH)3. The effluents are discharged onto the open land or put into the sewage system. These industries are the big source of chromium (VI) pollution in the environment. Chromium (VI) is highly toxic and is known to cause cancer.

93. The temperature in the incinerator of industrial waste products has a range:

• A. 900-1000°C
• B. 250-500°C
• C. 950-1300°C
• D. 500-900°C

Explanation: A general process of high temperature incineration system consists of a rotary kiln which accepts all types of wastes including liquid, solid or sludge. The wastes are burned at temperatures between 650° to 1100°C. Ash from the rotating chamber is collected at waste tank and the remaining liquid gaseous materials are passed to the secondary chamber. This chamber is non-rotating and hence the temperature range of 950° to 1300°C is maintained.

94. Which part of atmosphere is near to the earth:

• A. Thermosphere
• B. Troposphere
• C. Mesosphere
• D. Stratosphere

Explanation: The five main layers are the troposphere (closest to earth), stratosphere, mesosphere, thermosphere, and exosphere(farthest from earth).

95. Thickness of atmosphere is:

• A. 100 km
• B. 500 km
• C. 1000 km
• D. 1500 km

Explanation: The layer of gases surrounding the earth is called atmosphere. It consists of various gases in different proportions i.e., N2 (78%), O2 (21%), Ar (0.9 %), CO2 (0.03 %) and trace amounts of H2, O3, CH4, CO, He, Ne, Kr and Xe. It also contains varying amounts of water vapours. Its thickness is about 1000 km above the surface of the earth and half of its mass is concentrated in the lower 5.6 km.

96. How much fresh water is used for domestic purpose:

• A. 8%
• B. 23%
• C. 69%
• D. 100%

Explanation: Oceans contain 97% of earth's water but because of high salt contents this water cannot be used for human consumption. The polar ice caps and glaciers consist of 2% of the earth's total water supply. Only 1% of the total earth's water resources are available as fresh water i.e., surface water; river, lake, stream and ground water. The fresh water is being used by agriculture (69%), industry (23%) and for domestic purposes (8%).

97. The most abundant element in the earth crust is:

• A. O
• B. Si
• C. Al
• D. Fe

Explanation: The 99.5 % mass of the lithosphere is made of 11 elements, which are oxygen (~ 46.60 %), Si (~27.72 %), Al (8.13 %), Fe (5.0 %), Ca (3.63 %), Na (2.83 %), K (2.59 %), Mg (2.09 %) and Ti, H2 and P (total less than 1 %). The elements present in trace amounts (0.1 to 0.02 %) are C, Mn, S, Ba, Cl, Cr, F, Zr, Ni, Sr and V.

98. The residence time of NO is:

• A. Few hours
• B. 1day
• C. 3 days
• D. 4 days

Explanation: The residence time of NO and NO2 in the atmosphere are 4 and 3 days respectively.

99. The mean residence time of methane (CH4) in atmosphere is:

• A. 1-2 years
• B. 3-4 years
• C. 3-5 years
• D. 3-7 days

Explanation: Another natural source of methane is the anaerobic decomposition of organic matter by bacteria in water sediments and in soils. Methane has a mean residence time of about 3 -7 years in the atmosphere.

100. Ozone depletion is mainly due to the reaction of ozone (O3) with:

• A. O2
• B. CFCs
• C. SO2
• D. All of these

Explanation: Chlorofluorocarbons used as refrigerants in air conditioning and in aerosol sprays are inert in the troposphere but slowly diffuse into stratosphere, where they are subjected to ultraviolet radiation generating ClO free radicals. Chlorofluorocarbons (CFCs) play an effective role in removing O3 in the stratosphere .A single chloride free radical can destroy upto 100,000 ozone molecules.