Free Environmental Chemistry MCQs with Answers

81. Which method is used to remove permanent hardness of water:

• A. Aeration
• B. Coagulation
• C. Ion exchange
• D. Chlorination

Explanation: The surface or ground water may also contain calcium and magnesium salts which make the water hard. The hard water is then appropriately treated to remove Ca2+ and Mg2+.

82. To avoid, formation of toxic compounds with chlorine which of the followings is better to use as a disinfectant of water:

• A. O3
• B. ClO3
• C. Both
• D. None

Explanation: Chlorine is frequently used to disinfect water. Chlorine treatment is very effective in killing the pathogens that may cause serious water-borne diseases such as typhoid and cholera. Chlorination of water containing organic materials also forms some organic compounds which are toxic. To avoide the formation of toxic compounds with chlorine, ozone or chlorine dioxide is used for the disinfection of water.

83. Ecosystem is a smaller unit of:

• A. Lithosphere
• B. Hydrosphere
• C. Biosphere
• D. Atmospheric

Explanation: Biosphere is the region of earth capable of supporting life. It includes lower atmosphere, the oceans, rivers, lakes, soils and solid sediments that actively interchange materials with all types of living organisms i.e., human beings, animals and plants. Ecosystem is a smaller unit of biosphere which consists of community of organisms and their interaction with environment i.e., animals, plants and microorganisms which lie in a definite zone

84. The coagulant used in the purification of potable water is:

• A. Alum
• B. Nickle sulphate
• C. Copper sulphate
• D. Barium sulphate

Explanation: The materials which are suspended or present in the colloidal form in raw water are removed by coagulation. The coagulant such as aluminium sulphate or alum is added to the raw water, which causes the precipitation of suspended impurities.

85. Newspaper can be recycled again and again, by how many times:

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: The largest item which is recycled is newspaper and in its recycling process the release of chlorine or other bleaching acids and organic solvents is significantly less as compared to formation of these compounds during the processing of virgin newspaper.To improve the whiteness of the recycled newspaper it is blended with the virgin newspaper or sometimes treated with peroxides and hydrosulphites. In recycling process the fibre of the newspaper becomes shorter so it can be recycled again and again for five times.

86. Which of the following is not common domestic materials which are recycled:

• A. Paper
• B. Iron
• C. Glass
• D. Plastics

Explanation: In recycling some of the used or waste materials are not discarded after their initial use but are processed so that they can be used again. The purpose of recycling is to conserve sources such as raw material and energy. The volume of the waste is also much reduced by recycling of the materials.The most common domestic materials that are recycled are paper, plastic, glass and aluminium. Iron is not recycled.

87. The normal amount of overhead ozone is about:

• A. 335 DU
• B. 340 DU
• C. 345 DU
• D. 350 DU

Explanation: The amount of ozone in the atmosphere is expressed in Dobson units (DU). The normal amount of overhead ozone is about 350 DU.

88. When ground water seeps in the landfill a mixture of dissolved, suspended and microbial contaminants is formed, this mixture is called:

• A. Rancidity
• B. Incinerate
• C. Refuse
• D. Leachate

Explanation: The municipal solid waste is mainly disposed off by dumping it in a landfill. The landfill is a large hole in the ground or even a bare piece of land. When the landfill becomes full with waste it is covered by soil or clay. The ground water which seeps in the landfill and liquid from the waste itself all percholate through the refuse producing leachate. The leachate contains dissolved, suspended and microbial contaminants.

89. The gas that binds strongly with hemoglobin is:

• A. Carbon monoxide
• B. Carbon dioxide
• C. Methane
• D. Nitrogen oxide

Explanation: Carbon monoxide binds to hemoglobin much more strongly than oxygen. Its presence keeps oxygen from binding to hemoglobin. Carbon monoxide is highly poisonous gas and causes suffocation if inhaled. It binds blood haemoglobin more strongly than oxygen thus excluding oxygen from normal respiration.

90. The concentration of dissolved oxygen in water ranges from:

• A. 4-8 ppm
• B. 6-10 ppm
• C. 8-10 ppm
• D. 0.4-0.8 ppm

Explanation: In water the most important oxidizing agent is dissolved molecular oxygen (O2) the concentration of which ranges from 4 - 8 ppm. The organic matter is oxidized with the help of this dissolved oxygen in water.It is a parameter to determine the quality of water. The dissolved oxygen value less than 4 ppm indicates that water is polluted.