Free Environmental Chemistry MCQs with Answers

1. CFCs is used in:

• A. Refrigeration
• B. Aerosol spray
• C. Plastic foam industry
• D. All of above

Explanation: Chlorofluorocarbons (CFCs) are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine. They are used in the manufacture of aerosol sprays, blowing agents for foams and packing materials, as solvents, and as refrigerants.

2. Identify greenhouse gases:

• A. CH4 and O2
• B. CO2 and H2O Vapours
• C. NO2 and H2O Vapours
• D. CH4 and O3

Explanation: This is correct as it includes both carbon dioxide (CO2) and water vapor (H2O), which are major greenhouse gases contributing to the greenhouse effect on Earth.

3. Name which one of the following gas is not pollutant?

• A. Sulphur dioxide
• B. Carbon monoxide
• C. Carbon dioxide
• D. Nitrogen dioxide

Explanation: Among sulfur dioxide (SO2), carbon monoxide (CO), carbon dioxide (CO2), and nitrogen dioxide (NO2), carbon dioxide (CO2) is not typically considered an air pollutant in the same sense as the others.Carbon dioxide is a naturally occurring gas in the Earth's atmosphere and is essential for life on Earth. It is produced through natural processes such as respiration and volcanic eruptions, as well as human activities such as combustion of fossil fuels and deforestation. While carbon dioxide is a greenhouse gas and contributes to climate change when present in excessive amounts, it is not directly toxic to humans at typical ambient concentrations.On the other hand, sulfur dioxide, carbon monoxide, and nitrogen dioxide are all considered air pollutants due to their harmful effects on human health and the environment.

4. Peroxyacetyl Nitrate (PAN) is an irritant to human beings and it affects:

• A. Eyes
• B. Nose
• C. Stomach
• D. Skin

Explanation: Nose is correct because Peroxyacetyl Nitrate (PAN) primarily affects the respiratory system, causing irritation to the nose, throat, and lungs.

5. Which of the following is not a heavy industry?(Environmental chemistry,Components of Environment)

• A. iron
• B. fertilizer
• C. paper
• D. none

Explanation: This option is correct. All three options (a) iron, (b) fertilizer, and (c) paper can be considered heavy industries, as they involve large-scale production processes and infrastructure. Therefore, there isn't an option that is not a heavy industry among the given choices.Let's examine why other options are incorrect.(a) Iron - This is considered a heavy industry because it involves the extraction and processing of raw materials like iron ore, which are typically heavy and require significant machinery and infrastructure for mining, refining, and manufacturing steel products.(b) Fertilizer - Fertilizer production can be considered a heavy industry due to the large-scale chemical processes involved in manufacturing various types of fertilizers, which often require substantial energy inputs and industrial facilities.(c) Paper - Paper production is generally not classified as a heavy industry. While it involves manufacturing processes, including pulping, pressing, and drying, these processes typically do not require as much heavy machinery or energy-intensive operations as those found in industries like iron or fertilizer production.(Environmental chemistry,Components of Environment)

6. Which of the following is a macronutrient?

• A. boron
• B. iron
• C. copper
• D. carbon

Explanation: Carbon is indeed a macronutrient. It is one of the fundamental building blocks of all organic molecules, including carbohydrates, proteins, lipids, and nucleic acids, which are essential components of living organisms. Carbon is obtained through the consumption of organic matter in food and is a primary source of energy for living organisms. Now we'll look at why other options are incorrect.The correct answer is (d) carbon.Explanation:(a) Boron: Boron is a mineral and is considered a micronutrient, not a macronutrient. While it is essential for plant growth, it is required in very small amounts.(b) Iron: Iron is also a mineral and is classified as a micronutrient. It is essential for human health, particularly for the production of red blood cells, but it is needed in relatively small quantities compared to macronutrients.(c) Copper: Like boron and iron, copper is a mineral and falls under the category of micronutrients. It is required in trace amounts for various physiological functions in humans and other organisms.(Environmental chemistry,Components of Environment )

7. Residence time of methane in the atmosphere is?

• A. 3-7 days
• B. 2-3 days
• C. 3-7 years
• D. 2-3 years

Explanation: Methane (CH₄) is a greenhouse gas that traps heat in the atmosphere, contributing to climate change.It is emitted from various sources, including agriculture, waste decomposition, fossil fuel extraction and use, and biomass burning.Once released, methane undergoes chemical reactions in the atmosphere, primarily with hydroxyl radicals (OH). This process breaks down methane and removes it from the atmosphere.However, this removal process takes time. The average residence time of methane in the atmosphere is estimated to be between 9 and 12 years, although estimates can vary based on factors like atmospheric conditions and location.Therefore, options (a), (b), and (d) are incorrect because they significantly underestimate the actual residence time of methane.(Environmental chemistry,Introduction and Types of Pollution Factors affecting Water Quality )

8. Major causes of SO2 on global scale?

• A. volcanoes
• B. electric sparks
• C. combustion
• D. all

Explanation: Approximately 50% of global SO2 emissions come from volcanic eruptions.(Environmental chemistry,Introduction and Types of Pollution Factors affecting Water Quality ) Q8: Hypochlorous acid is used for disinfecting the water. It reacts with the dissolved ammonia producing?(a) NH2Cl (b) NHCl2 (c) NCL3 (d) All of the above Answer: (d) All of the above:HClO + NH₃ → NH₂Cl + H₂ONHCl₂ (dichloramine): Dichloramine can form as a byproduct of the reaction, but it is less stable than mono chloramine and is usually present in much lower concentrations.NCl₃ (trichloramine): Trichloramine is another byproduct that can form under certain conditions, but it is even less stable than dichloramine and is typically present in even lower concentrations.all three products can potentially form in the reaction, mono chloramine is the main product and the others are usually present in much lower concentrations.

9. Acid present in the acid rain may be?

• A. H2SO4
• B. HNO3
• C. both a & b
• D. none

Explanation: (a) H₂SO₄ (sulfuric acid): This is the primary acid found in acid rain, accounting for roughly 60% of the acidity. It forms when sulfur dioxide (SO₂) emitted from fossil fuel combustion and volcanic eruptions reacts with water vapor and oxygen in the atmosphere.(b) HNO₃ (nitric acid): This contributes about 20% of the acidity in acid rain. It forms when nitrogen oxides (NOx) released from vehicle emissions and industrial processes react with water vapor and oxygen in the air.Now we'll look at why other options are incorrect.(d) none: As explained above, both H₂SO₄ and HNO₃ are present in acid rain.(b) HNO₃ only: While nitric acid is significant, sulfuric acid makes up the majority of acidity.(Environmental chemistry,Introduction and Types of Pollution Factors affecting Water Quality ) Q10: The yellow color in photochemical smog is due to the presence of? (a) dinitrogen oxide (b) nitrogen dioxide (c) chlorine gas (d) chlorine dioxideAnswer:(b) Nitrogen dioxide (NO₂): This gas absorbs blue light wavelengths, giving the remaining scattered light a yellowish or brownish hue. This is the main contributor to the characteristic color of photochemical smog.Now we'll look at why other options are incorrect.(a) Dinitrogen oxide (N₂O): While N₂O does contribute to greenhouse gas effects, it doesn't have a significant impact on the color of smog.(c) Chlorine gas (Cl₂): This gas is typically greenish-yellow, but its concentrations in smog are usually too low to have a noticeable impact on color.(d) Chlorine dioxide (ClO₂): Similar to chlorine gas, its concentrations are generally too low to affect the overall color of smog.(Environmental chemistry,Introduction and Types of Pollution Factors affecting Water Quality )

10. Incineration of municipal waste is carried out in the temperature range of ?

• A. 250 - 500°C
• B. 500 - 900°C
• C. 950 - 1300°C
• D. 900 - 1000°C

Explanation: This is the most common temperature range for modern municipal waste incinerators. At these temperatures, organic matter is efficiently combusted, and the destruction of pollutants like dioxins and furans is maximizedNow we'll look at why other options are incorrect.(a) 250 - 500°C: This temperature range is too low for efficient and complete combustion of municipal waste. At these temperatures, organic materials in the waste may not fully burn, leading to the formation of harmful pollutants and incomplete combustion products.(b) 500 - 900°C: While some incineration technologies may operate at the lower end of this range (around 750-850°C), it's generally considered the minimum temperature for ensuring adequate destruction of organic matter and minimizing pollutant formation. However, complete combustion and destruction of certain pollutants like dioxins often require higher temperatures.(c) 950 - 1300°C: While falling within the generally acceptable range, it's not as representative as option (d). Most incinerators operate at slightly lower temperatures within this range depending on specific waste composition and emission control technologies employed.(Environmental chemistry,Chemistry of Troposphere and Stratosphere)