Free Environmental Chemistry MCQs with Answers

51. Which one is not included under greenhouse gases?

• A. CO2
• B. CH4
• C. Chlorofluorocarbons
• D. SO2

Explanation: Sulfur dioxide (SO2) is primarily known as a precursor to acid rain. In the atmosphere, it can form sulphate aerosols which actually reflect sunlight and have a slight cooling effect, counteracting the warming caused by greenhouse gases.

52. _ is the uppermost region of the earth's atmosphere.

• A. Stratosphere
• B. Troposphere
• C. Exosphere
• D. Ionosphere

Explanation: The exosphere is the final frontier of the Earth's atmosphere. It is the outermost layer, where the atmosphere thins out and merges with the vacuum of outer space.

53. Which region of the atmosphere is the coldest?

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

Explanation: The mesosphere is the layer of the atmosphere where temperature decreases with altitude. The top of this layer, the mesopause, is the coldest place on Earth, with temperatures dropping to around -100 °C.

54. Choose the compound that is always present in photochemical smog:

• A. O3
• B. CO
• C. CO2
• D. SO2

Explanation: Photochemical smog is characterized by its high concentration of oxidants, the most abundant of which is ozone (O3). This ground-level ozone is formed from the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight.

55. Which statement is not related to environmental pollution?

• A. Direct or indirect change in any component of the biosphere
• B. Undesirable change in the physical characteristics of the air
• C. Undesirable change in the chemical characteristics of the water
• D. Not affecting adversely the industrial progress

Explanation: Environmental pollution is defined by the adverse effects it has on the environment and living organisms. While industrial progress is often linked to pollution, the concept of industrial progress itself is economic and not a definitional part of pollution.

56. The science of all the relations of all organisms to their environment is called:

• A. Biology
• B. Botany
• C. Environmental chemistry
• D. Ecology

Explanation: Ecology is the branch of biology that studies the interactions among organisms and between organisms and their physical environment. It encompasses all aspects of these relationships.

57. Which of the following is a component of the ecosystem?

• A. Inorganic substances
• B. Organic substances
• C. Animals and plants only
• D. All of the above

Explanation: An ecosystem is composed of both biotic (living) components, such as plants and animals, and abiotic (non-living) components. The abiotic components include all physical and chemical factors, such as inorganic and organic substances, water, and sunlight.

58. Which of the following forms of energy is trapped by autotrophic organisms?

• A. Mechanical energy
• B. Electrical energy
• C. Radiant energy
• D. Vibrational energy

Explanation: Autotrophic organisms, primarily plants and algae, capture radiant energy from the sun through the process of photosynthesis. They use this light energy to convert inorganic substances into chemical energy stored in organic molecules.

59. In a biological ecosystem, which of the following is used by organisms?

• A. Water
• B. Sunlight
• C. Minerals
• D. All of the above

Explanation: All living organisms in an ecosystem require a combination of resources to survive and thrive. These include water for metabolic processes, sunlight as the primary energy source or producers, and minerals as essential nutrients for growth and function.

60. Which of the following processes involves the use of an organic compound as an electron acceptor?

• A. Aerobic respiration
• B. Anaerobic respiration
• C. Fermentation
• D. Glycolysis

Explanation: In fermentation, which occurs in the absence of an external electron acceptor like oxygen, an organic molecule (such as pyruvate or acetaldehyde) generated during glycolysis is used as the final electron acceptor. This regenerates the NAD+ needed for glycolysis to continue.