Free Environmental Chemistry MCQs with Answers

71. Which of the following substances acts as a gaseous pollutant?

• A. NO
• B. NO2
• C. SO2
• D. All of the above

Explanation: Nitric oxide (NO), nitrogen dioxide (NO2), and sulfur dioxide (SO2) are all major gaseous air pollutants. They are primarily produced by the combustion of fossil fuels and contribute to problems like smog and acid rain.

72. Which of the following metals acts as a pollutant?

• A. Hg (Mercury)
• B. Pb (Lead)
• C. Cd(Cadmium)
• D. All of the above

Explanation: Mercury, lead, and cadmium are all heavy metals that are toxic to living organisms even at low concentrations. They are persistent environmental pollutants that can be released from various industrial activities.

73. Synthetic organic chemicals can cause which of the following problems:

• A. Nausea
• B. Dizziness
• C. Blindness
• D. All of the above

Explanation: Ozone is produced in most of the tropical regions by the photochemical reactions of oxygen, from where it is transported to polar regions. It acts as a pollutant and causes various health problems i.e., damages eyes and aggravates asthma, decreases the elasticity of lung tissues, coughing, chest discomfort, etc.

74. Which of the following is considered as cause of pollution:

• A. Rapid increase in population
• B. Industrialization
• C. Transportation
• D. All of the above

Explanation: Rapid increase in population leads to increase in need of basic resources like food and shelter leading to burning of more fossil fuels, deforestation etc which cause pollution.Harmful chemicals produced from industry and transportation are a leading cause of pollution.

75. Which of the following is primary pollutant:

• A. H2SO4
• B. N2O
• C. H2CO3
• D. SO2

Explanation: The waste products given out from chimneys of industrial units and exhaust of automobiles may contain gases such as sulphur dioxide, sulphur trioxide, nitrogen oxides, carbon monoxide, hydrocarbons, ammonia, compounds of fluorine and radioactive materials. These waste products are called primary pollutants.

76. In which of the following layer of atmosphere there is more thickness of ozone:

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

Explanation: Ozone, O3, is a gas having low boiling point. It is present in small concentrations throughout the atmosphere.The amount of ozone in the atmosphere is expressed in Dobson units (DU). The normal amount of overhead ozone is about 350 DU. The ozone layer, 25 - 28 km high, in the stratosphere surrounds the globe and filters most of the harmful ultraviolet (UV) rays in the sunlight before they could reach on the earth.

77. Which of the following air pollutants is quiet killer:

• A. CO2
• B. CO
• C. NO2
• D. N2O4

Explanation: Carbon monoxide is highly poisonous gas and causes suffocation if inhaled. It binds blood haemoglobin more strongly than oxygen thus excluding oxygen from normal respiration. The CO poisoning can be reversed by giving high pressure oxygen. Exposure to high concentration of CO results in headache, fatigue, unconsciousness and eventually death (if such exposure is sustained for longer period). It is a colourless and odourless gas hence there is no way to detect it in case of leakage etc. so it is called quiet killer.

78. The cause of water pollution is:

• A. Presticides
• B. Detergents
• C. Tanneries
• D. All

Explanation: The human activities such as livestock waste, landfills, agriculture, pesticides, oil leaks and spills, disposal of industrial effluents on open land, water bodies, septic tanks, detergents, mining, petroleum and natural gas production may result in the contamination of the surface and ground waters.

79. The pH value of the acid rain is in the range of:

• A. 6.5 - 7.0
• B. Less than 5.6
• C. Less than 5.0
• D. Less than 7.0

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

80. Which of the following factors help to measure quality of water:

• A. DO
• B. BOD
• C. COD
• D. All of above

Explanation: 1. Dissolved Oxygen (DO)In water the most important oxidizing agent is dissolved molecular oxygen (O2) the concentration of which ranges from 4 - 8 ppm. The organic matter is oxidized with the help of this dissolved oxygen in water.It is a parameter to determine the quality of water. 2. Biochemical Oxygen Demand (BOD)It is the capacity of organic matter in natural water to consume oxygen within a period of five days. The value of BOD is the amount of oxygen consumed as a result of biological oxidation of dissolved organic matter in the sample. 3. Chemical Oxygen Demand (COD)The organic content of water which consumes oxygen during chemical oxidation is evaluated by its chemical oxygen demand. The oxygen demand of water can be determined directly by treating it with dichromate ions Cr2O7 2- which is a powerful oxidizing agent.