Free Environmental Chemistry MCQs with Answers

101. In human liver which substance cause cancer:

• A. Chloroform
• B. Methane
• C. Carbon dioxide
• D. H2SO3

Explanation: Chloroform CHCl3 is formed when hypochlorous acid reacts with organic matter (humic acid) dissolved in water. Chloroform is suspected liver carcinogen and also has negative reproduction and development effects in humans. The risk of bladder and rectal cancer increases by drinking chlorinated water.

102. The pH range of the truely acidic rain is:

• A. 7-6.5
• B. 6.5-6
• C. 6-5.6
• D. Less than 5.6

Explanation: The pH of unpolluted rain water should be 5.6.The rain water has pH less than 5 is considered truly acidic.

103. Peroxyacetylinitrate (PAN) is an irritant to human beings and it affects:

• A. Eyes
• B. Ears
• C. Stomach
• D. Nose

Explanation: The overall result of photochemical smog in afternoon is the built up of oxidizing agents such as H2O2, HNO3, peroxyacetyl nitrate (PAN) and ozone in the air. PAN is an eye irritant and is also toxic to plants.

104. To avoid the formation of toxic compounds with chlorine which substance is used for disinfecting water:

• A. KMnO4
• B. O3
• C. Alums
• D. Chloramines

Explanation: To avoide the formation of toxic compounds with chlorine, ozone or chlorine dioxide is used for the disinfection of water.

105. A single chloride free radical can destroy how many ozone molecules:

• A. 100
• B. 100000
• C. 10000
• D. 10

Explanation: A single chloride free radical can destroy upto 100,000 ozone molecules.

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

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

Explanation: Leather tanneries 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.

107. In purification of potable water the coagulant used is:

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

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.

108. The temperature in the non-rotating chamber in the incineration of industrial and hazardous waste process has a range:

• A. 900 to 1000°C
• B. 250 to 500°C
• C. 950 to 1300°C
• D. 500 to 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. In this chamber organic molecules are completely destroyed.

109. Which of the following is an application of chemistry in the field of medicine?

• A. Desalination of seawater
• B. Production of biofuels
• C. Development of new pharmaceutical drugs
• D. Extraction of metals from ores

Explanation: Chemistry plays a crucial role in the development of new pharmaceutical drugs. Medicinal chemists use their knowledge of chemical properties and interactions to design and synthesize new compounds that can be used to treat diseases and improve human health. They study the structure-activity relationships of various molecules to understand how they interact with biological targets and optimize their effectiveness and safety.Desalination of seawater (option A) involves removing salts from seawater to make it suitable for drinking or agricultural purposes. This process typically relies on physical separation techniques such as reverse osmosis and distillation, which are more closely related to chemical engineering than pure chemistry.Production of biofuels (option B) involves the conversion of biomass or organic waste into usable fuels. While chemistry is involved in the conversion processes, biofuel production is a multidisciplinary field that incorporates biology, engineering, and environmental science.Extraction of metals from ores (option D) falls under the field of metallurgy, which is a branch of materials science and engineering. Although chemistry is involved in the extraction and purification processes, this application is more focused on understanding the properties and behavior of metals rather than developing pharmaceutical drugs.Therefore, option C is the most appropriate choice as it specifically highlights an important application of chemistry in the field of medicine.

110. Which of the following is secondary pollutant?

• A. CO
• B. SO2
• C. PAN
• D. NO2

Explanation: A secondary pollutant is a pollutant that is not emitted directly into the atmosphere but is formed through chemical reactions in the air. It is derived from primary pollutants that are emitted directly from a source. Among the options you mentioned, ozone (O3) is a secondary pollutant. It is formed through chemical reactions involving primary pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Ozone is a harmful pollutant when present at ground level, contributing to smog and respiratory issues.Primary pollutants are those which are emitted directly from their sources. Examples of primary pollutants are oxides of sulphur and nitrogen, carbon monoxide, ammonia, hydrocarbons, ammonia, compounds of fluorine and radioactive materials. Secondary pollutants are either formed by the atmospheric transformation of primary pollutants or other chemical compounds. Examples of secondary pollutants are carbonic acid, hydrofluoric acid, sulphuric acid, ozone, aldehydes and ketones, peroxybenzol and PeroxyAcetyl Nitrate (PAN). Therefore, option C is correct.Option A, B and D are incorrect because as stated above, they are all examples of primary pollutants.