Environmental Science MCQ – Asked in Previous Years, WBCS Mains

Answer –B. create P. D. between the two electrodes.
Explanation-
▪ In a hydrogen-oxygen fuel cell, the combustion of hydrogen occurs to create a potential difference (P. D.) between the two electrodes. This P. D. is then used to generate electricity.

▪ The other options are incorrect. Hydrogen-oxygen fuel cells do not generate heat, produce high-purity water, or remove absorbed oxygen.

▪ Here is a more detailed explanation of how a hydrogen-oxygen fuel cell works:

• The hydrogen and oxygen are fed into the fuel cell at the anode and cathode, respectively.

• The hydrogen is oxidized at the anode, releasing electrons.
• The electrons travel through an external circuit, creating an electrical current.

• The oxygen is reduced at the cathode, combining with the electrons to form water.
• The water is then emitted from the fuel cell.

▪ The P. D. between the two electrodes is created by the difference in the oxidation potential of hydrogen and the reduction potential of oxygen.

▪ The oxidation potential is the energy required to remove an electron from an atom or molecule, while the reduction potential is the energy released when an electron is added to an atom or molecule.

▪ The P. D. between the two electrodes is what drives the electrochemical reaction in the fuel cell, and it is this reaction that produces electricity.

Answer – B. Many of the birds’ eggs laid did not hatch.
Explanation-
▪ DDT (dichloro-diphenyl-trichloroethane) is an insecticide that was widely used in the past. One of the significant impacts of DDT usage was its adverse effect on bird populations, particularly birds of prey and their reproductive success.

▪ DDT accumulates in the food chain, and when birds consume contaminated prey, the chemical interferes with their calcium metabolism. As a result, the shells of their eggs become thinner and weaker, leading to a higher rate of egg breakage and reduced hatchability. This decline in hatchability contributed to a significant decline in bird populations in areas where DDT was extensively used.

Answer – A. Indonesia
Explanation-
▪ As of April 2022, Indonesia is the world’s largest producer of palm oil. Palm oil is a versatile vegetable oil derived from the fruit of oil palm trees. Indonesia has vast areas of land dedicated to oil palm plantations, and its tropical climate provides favorable conditions for palm oil production. The country’s palm oil industry plays a significant role in its economy, but it has also raised concerns regarding deforestation, habitat destruction, and environmental impacts due to the expansion of plantations.

Answer – B. Decibel
Explanation-
▪ Noise pollution, which refers to excessive or disruptive noise that can be harmful to human health and the environment, is measured using a sound meter. The unit used to measure noise levels is the decibel (dB).

▪ The decibel scale quantifies the intensity or loudness of sound. It is a logarithmic scale, which means that a small change in decibel value represents a significant change in sound intensity. Higher decibel levels indicate louder and more intense sounds, while lower decibel levels indicate quieter sounds.

Answer – D. non-biodegradable pollutant
Explanation-DDT (dichloro-diphenyl-trichloroethane) and aluminum cans are examples of non-biodegradable pollutants. Non-biodegradable pollutants are substances that persist in the environment for a long time without naturally breaking down or decomposing. DDT is a pesticide that remains in the environment for an extended period, accumulating in the food chain and causing ecological and health concerns. Aluminum cans, although recyclable, can take hundreds of years to decompose in the environment if not properly managed.

Answer –B. Ozone
Explanation-
▪ Ozone is considered a secondary air pollutant. It is not directly emitted into the atmosphere but is formed through chemical reactions involving primary pollutants in the presence of sunlight.

▪ The primary pollutants, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs), react in the presence of sunlight to form ozone through a complex series of chemical reactions. Ozone can have detrimental effects on human health and the environment, particularly at ground level, where it contributes to the formation of smog.

Answer – C. Mist
Explanation-
▪ Mist is a liquid form of aerosol. An aerosol refers to a suspension of fine solid or liquid particles in a gas. While fumes, dust, and smoke are examples of aerosols, they exist in different states.

▪ Fumes consist of solid particles that are formed when a material vaporizes or sublimates. Dust consists of solid particles that are larger and more visible than fumes. Smoke consists of tiny particles resulting from the incomplete combustion of organic matter. Mist, on the other hand, is composed of liquid droplets suspended in the air, typically formed by condensation or dispersion of liquid particles.

Answer – B. Accumulation of salts in the soil
Explanation-
▪ Salinization refers to the accumulation of salts in soil, leading to an increase in soil salinity. This typically occurs when irrigation water contains high levels of salts, and as the water evaporates or is taken up by plants, the salts remain behind, gradually accumulating in the soil. Excessive salinity in soil can negatively impact plant growth and agricultural productivity, as high salt concentrations can interfere with water uptake and nutrient availability for plants.

Answer – A. Natural resources
Explanation-
▪ Renewable energy is generated from natural resources that are naturally replenished or constantly available in the environment. These resources include sunlight (solar energy), wind, water (hydropower), biomass, geothermal heat, and certain forms of biofuels. Unlike fossil fuels, which are finite and depletable, renewable energy sources offer a sustainable and environmentally friendly alternative for meeting energy needs.

Answer – A. Benzene and Formaldehyde
Explanation-
▪ VOCs (Volatile Organic Compounds) are a group of chemicals that readily vaporize at room temperature. While many VOCs can have various health effects, including respiratory irritation, some VOCs are known or suspected carcinogens.

▪ Benzene and Formaldehyde are examples of VOCs that have been linked to cancer. Benzene is a known carcinogen found in gasoline, vehicle emissions, and certain industrial processes. Formaldehyde, commonly used in building materials and household products, is classified as a probable human carcinogen by international agencies.