Free Environmental Chemistry MCQs with Answers

61. Which of the following statements is not related to the decomposition phenomenon occurring in nature?

• A. Decomposition is due to autotrophic organisms
• B. Decomposition involves bacteria and fungi
• C. During decomposition, organisms carry out specific reactions
• D. Many species of decomposers are present in the biosphere

Explanation: Decomposition is the breakdown of dead organic matter, a process carried out by heterotrophic organisms, primarily bacteria and fungi, which are known as decomposers. Autotrophic organisms are producers that create organic matter, they do not decompose it.

62. Which of the following statements is not true with respect to the role of matter undergoing decomposition?

• A. Decomposed matter increases soil fertility
• B. It provides a texture which is favorable for plant growth
• C. Decomposition products may be harmful if present in excess
• D. In high concentration, the decomposition product may increase the photosynthesis

Explanation: While the products of decomposition (like CO2 and mineral nutrients) are essential for photosynthesis, the decomposition process itself does not directly increase the rate of photosynthesis. High concentrations of decomposition products can even be harmful.

63. Which of the following biogeochemical cycles is not a component of the ecosystem?

• A. Carbon cycle
• B. Potassium cycle
• C. Nitrogen cycle
• D. Oxygen cycle

Explanation: While potassium is an essential nutrient, its cycle is primarily a sedimentary cycle and is not considered one of the major gaseous biogeochemical cycles like the carbon, nitrogen, and oxygen cycles, which involve a significant atmospheric component.

64. Which of the following substances is most abundant component of atmospheric air?

• A. O2
• B. N2
• C. Ar
• D. CO2

Explanation: The Earth's atmosphere is composed of approximately 78% nitrogen gas (N2), making it by far the most abundant component. Oxygen makes up about 21%, and all other gases are present in much smaller amounts.

65. Which of the following processes is involved in getting back nitrogen into the atmosphere?

• A. Nitrification
• B. Denitrification
• C. Ammonification
• D. All of the above

Explanation: Denitrification is a microbial process where nitrate (NO3−) is reduced and ultimately converted back into molecular nitrogen gas (N2). This process, carried out by denitrifying bacteria, returns nitrogen to the atmosphere, completing the nitrogen cycle.

66. Which of the following processes is involved in nitrogen fixation?

• A. Non-symbiotic fixation of nitrogen
• B. Fixation by soil bacteria
• C. Fixation by yeast
• D. All of the above

Explanation: Nitrogen fixation is the conversion of atmospheric nitrogen (N2) into ammonia (NH3). This crucial process is primarily carried out by specialized soil bacteria, either living freely in the soil or in a symbiotic relationship with plants.

67. Which of the following is a domain of industrial ecology?

• A. The materials extractor
• B. The materials processor
• C. The consumer
• D. All of the above

Explanation: Industrial ecology is a holistic field that studies the flow of materials and energy through industrial systems. It considers all stages of the product life cycle, from raw material extraction to processing, consumption, and disposal, as interconnected parts of a single system.

68. Which of the following is an important aspect of industrial ecology?

• A. Minimising air emissions
• B. Minimising liquid waste
• C. Designing for energy efficiency
• D. All of the above

Explanation: Industrial ecology aims to create industrial systems that are more sustainable by mimicking natural ecosystems. Key aspects of this include minimizing all forms of waste and emissions, and maximizing energy and material efficiency throughout the system.

69. Pesticide residues appear in which of the following foods?

• A. Milk
• B. Fruit
• C. Fish
• D. All of the above

Explanation: Pesticide residues can contaminate various parts of the food web. They can be present on the surface of fruits and vegetables, bioaccumulate in the fatty tissues of animals (leading to contamination of milk), and concentrate in aquatic ecosystems, contaminating fish.

70. Which of the following acids is the main component of acid mine drainage?

• A. HCl
• B. HNO3
• C. H2SO4
• D. CH3COOH

Explanation: Acid mine drainage is formed when sulfide minerals (like pyrite, FeS2) present in coal and metal ores are exposed to air and water. This triggers their oxidation, a process that produces sulfuric acid (H2SO4), leading to highly acidic wastewater.