Free Environmental Chemistry MCQs with Answers

191. Which of the following compounds is responsible for the depletion of ozone layer?

• A. Chlorofluorocarbons
• B. Carbon tetrachlorie
• C. Methane
• D. Hydroflorocarbons

Explanation: Factual recall.Chlorofluorocarbons (CFCs) have a significant effect on the ozone layer. When released into the atmosphere, CFCs can reach the stratosphere, where they undergo photodissociation due to the absorption of ultraviolet (UV) radiation. This process releases chlorine and bromine atoms.These chlorine and bromine atoms act as catalysts in ozone depletion reactions. They catalytically destroy ozone molecules, breaking them apart and reducing the overall concentration of ozone in the stratosphere.

192. The whiteness of the recycled newspaper is improved by treating it with:

• A. Sodium hydroxide
• B. Per oxides
• C. Super oxides
• D. Normal oxides

Explanation: A is incorrect as sodium hydroxide is not used for whitening of newspapers.B is correct as per oxides are used to whiten old newspapers.The hydrogen peroxide bleaching process results in not only increased brightness, but also in the improvement of paper physical properties. It is now well established that carboxylic acid groups are beneficial for the bonding of pulp fibers in paper and can increase the strength of paperC is incorrect as super oxides are not used to whiten newspapers.D is incorrect as normal oxides are not used to whiten newspapers.

193. The coagulant used in raw water to precipitate suspended impurities is:

• A. Caustic soda
• B. Lime water
• C. Alum
• D. Soda ash

Explanation: A is incorrect as caustic soda is not used as a coagulant.B is incorrect as lime water is not used as a coagulant,but is used to detect the presence of CO2 gas.C is correct as alum is used as a coagulant in raw water to remove suspended impurities.D is incorrect as soda ash is not used as a coagulant

194. Green house effect is NOT produced by the abundance of the gas called

• A. Methane
• B. CO2
• C. Nitrous oxide
• D. Sulphur dioxide

Explanation: The greenhouse effect is how heat is trapped close to Earth's surface by "greenhouse gases." Greenhouse gases include CO2, methane, and nitrous oxide which are options A, B, and C respectively. Option D, SO2, is an atmospheric pollutant produced by volcanic eruptions and combustion engines. It is mainly responsible for acid rain, not the greenhouse effect, making it the correct answer.

195. SO2 is responsible fir the formation of:

• A. Acid rain
• B. Green house effect
• C. Global warming
• D. Ozone depletion

Explanation: Acid rain: SO2 is a major contributor to the formation of acid rain. When released into the atmosphere, it reacts with water and other substances to form sulfuric acid, which can then fall to the Earth's surface as acid rain. Therefore, the correct option is "Acid rain" as SO2 is responsible for the formation of acid rain.

196. Chlorofluorocarbons are mainly responsible for:

• A. Air pollution
• B. Water pollution
• C. Acid rain
• D. Ozone layer depletion

Explanation: Chlorofluorocarbons (CFCs) are mainly responsible for ozone layer depletion.

197. C.F.C gases are produced from

• A. burning of coal
• B. burning of charcoal
• C. automobile engines
• D. refrigeration and air conditioning

Explanation: Chloroflorocarbons are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine. They react with the ozone and destroy it, making the layer thinner and allowing ultraviolet (UV) radiation to pass through it and fall on the earth's surface. This UV radiation can cause skin cancer and other ailments in humans and also affect plants and animals. The main source of CFC production is Coal combustion i.e. burning of coal. Among the given options, option A is correct because, unlike the rest, CFCs are released into the atmosphere, not produced.

198. Vehicular emissions, that are the major environmental concern, is

• A. CO2
• B. CO
• C. Low hydrocarbons
• D. All of them

Explanation: CO2 is the major vehicular emission responsible for causing the greenhouse effect and environmental pollution.

199. Tetraethyl lead (C2H2)4Pb is used as an antoknock agent and abandoned because of its hazardous product during the combustion of fuel. The hazardous product is

• A. CO2
• B. CO
• C. Lead
• D. Free radica ethyne (C2H2)

Explanation: TEL can cause chronic lead poisoning, and hence its hazardous product is lead.

200. Paper is a biodegradable material. It produces gas whose emission is environmentally objectionable. Which is that gas?

• A. CO2
• B. SO2
• C. CH4
• D. NO2

Explanation: When paper biodegrades, especially in the presence of oxygen, the primary gas emitted is carbon dioxide (CO2), due to the aerobic decomposition of its cellulose content. This process involves microorganisms breaking down the organic matter, releasing CO2 as a byproduct. Other gases like sulfur dioxide (SO2), methane (CH4), and nitrogen dioxide (NO2) are not typically emitted during the biodegradation of paper. SO2 is linked to burning sulfur-containing materials, CH4 is released in anaerobic conditions like landfills, and NO2 results from high-temperature combustion processes of fossil fuels.