PU CET Lahore (Engineering & CS) Chemistry Environmental Chemistry — Set 2

1. Question 1

   Q1. The BOD of a water sample is 5 mg/L. What does it indicate?

   • A) Low organic pollution
   • B) High organic pollution
   • C) Presence of toxic chemicals
   • D) High dissolved oxygen

   Answer: Low organic pollution

   Explanation: BOD (Biochemical Oxygen Demand) measures the oxygen required to break down organic matter; low BOD indicates low organic pollution.

2. Question 2

   Q2. What is the primary sink for CO2 in the atmosphere?

   • A) Oceans
   • B) Forests
   • C) Soil
   • D) Atmosphere

   Answer: Oceans

   Explanation: Oceans absorb CO2 through chemical reactions and biological processes, making them a primary sink.

3. Question 3

   Q3. The concentration of a pollutant is 2 mg/m³. What is its concentration in ppm?

   • A) 1 ppm
   • B) 2 ppm
   • C) 0.5 ppm
   • D) 4 ppm

   Answer: 2 ppm

   Explanation: 1 mg/m³ = 1 ppm for gases at standard conditions, assuming ideal gas behavior.

4. Question 4

   Q4. A water sample has a COD of 100 mg/L. What does it indicate?

   • A) Low organic pollution
   • B) High organic pollution
   • C) Presence of inorganic pollutants
   • D) High dissolved oxygen

   Answer: High organic pollution

   Explanation: COD (Chemical Oxygen Demand) measures the oxygen required to oxidize organic matter; high COD indicates high organic pollution.

5. Question 5

   Q5. What is the main cause of ozone layer depletion?

   • A) CO2 emissions
   • B) CFC emissions
   • C) CH4 emissions
   • D) N2O emissions

   Answer: CFC emissions

   Explanation: CFCs (chlorofluorocarbons) release chlorine atoms, which catalytically destroy ozone molecules, causing depletion.

6. Question 6

   Q6. The pE of a solution is 5. What is the ratio of oxidized to reduced species?

   • A) 10^5
   • B) 10^-5
   • C) 10^10
   • D) 10^-10

   Answer: 10^5

   Explanation: pE = log(ox/red), so ox/red = 10^(pE) = 10^5, using the Nernst equation.

7. Question 7

   Q7. A soil sample has a pH of 6. What is the pOH?

   • A) 8
   • B) 6
   • C) 4
   • D) 2

   Answer: 8

   Explanation: pH + pOH = 14, so pOH = 14 - pH = 14 - 6 = 8, using the water dissociation constant.

8. Question 8

   Q8. The concentration of a pollutant is 0.5 ppb. What is its concentration in ng/m³?

   • A) 0.5 ng/m³
   • B) 5 ng/m³
   • C) 50 ng/m³
   • D) 500 ng/m³

   Answer: 5 ng/m³

   Explanation: 1 ppb = 1 ng/L for gases or 1 μg/m³; assuming standard conditions, 0.5 ppb = 0.5 μg/m³ or 500 ng/m³, but for air, 1 ppb = 1 ng/L = 1 μg/m³ at STP, for an ideal gas.

9. Question 9

   Q9. What is the effect of heavy metals on aquatic life?

   • A) Increased growth rates
   • B) Toxicity and bioaccumulation
   • C) Improved water clarity
   • D) Enhanced nutrient cycling

   Answer: Toxicity and bioaccumulation

   Explanation: Heavy metals are toxic and can bioaccumulate in aquatic organisms, causing harm.

10. Question 10

    Q10. A wastewater sample has a TSS of 200 mg/L. What does it indicate?

    • A) Low suspended solids
    • B) High suspended solids
    • C) Presence of dissolved pollutants
    • D) High dissolved oxygen

    Answer: High suspended solids

    Explanation: TSS (Total Suspended Solids) measures the concentration of suspended particles; high TSS indicates high suspended solids.

11. Question 11

    Q11. What is the primary mechanism of pesticide degradation in soil?

    • A) Hydrolysis
    • B) Photolysis
    • C) Microbial degradation
    • D) Volatilization

    Answer: Microbial degradation

    Explanation: Microorganisms in soil degrade pesticides through enzymatic reactions, breaking them down into simpler compounds.

12. Question 12

    Q12. The DO of a water sample is 5 mg/L. What is its saturation percentage?

    • A) 50%
    • B) 25%
    • C) 75%
    • D) 100%

    Answer: 50%

    Explanation: Assuming a saturated DO of 10 mg/L at a given temperature, 5 mg/L is 50% saturation.

13. Question 13

    Q13. What is the effect of ocean acidification on marine life?

    • A) Increased calcification
    • B) Decreased calcification
    • C) Improved coral growth
    • D) Enhanced shell formation

    Answer: Decreased calcification

    Explanation: Ocean acidification decreases pH, reducing carbonate ion availability, making it harder for organisms to form calcium carbonate shells.

14. Question 14

    Q14. A air sample has a CO concentration of 10 ppm. What is its concentration in mg/m³?

    • A) 10 mg/m³
    • B) 20 mg/m³
    • C) 12 mg/m³
    • D) 15 mg/m³

    Answer: 12 mg/m³

    Explanation: 1 ppm CO = 1.25 mg/m³ (using molecular weight and ideal gas law), so 10 ppm = 12.5 mg/m³, approximately.

15. Question 15

    Q15. What is the main cause of groundwater pollution?

    • A) Agricultural runoff
    • B) Industrial waste disposal
    • C) Leaky landfills
    • D) All of the above

    Answer: All of the above

    Explanation: Various human activities, including agricultural runoff, industrial waste, and leaky landfills, can contaminate groundwater.

16. Question 16

    Q16. What is the primary sink for CO2?

    • A) Oceans
    • B) Atmosphere
    • C) Land
    • D) Biosphere

    Answer: Oceans

    Explanation: Oceans absorb CO2 through chemical reactions and biological processes, making them the primary sink

17. Question 17

    Q17. The ozone layer depletion is mainly caused by?

    • A) CO2
    • B) CFCs
    • C) CH4
    • D) N2O

    Answer: CFCs

    Explanation: CFCs release Cl atoms, which catalytically destroy O3 molecules, causing ozone layer depletion

18. Question 18

    Q18. The main greenhouse gas responsible for global warming is?

    • A) CO2
    • B) CH4
    • C) N2O
    • D) O3

    Answer: CO2

    Explanation: CO2 is the most prevalent greenhouse gas, contributing significantly to global warming

19. Question 19

    Q19. What is the purpose of adding lime to water?

    • A) To remove hardness
    • B) To increase pH
    • C) To remove turbidity
    • D) To decrease pH

    Answer: To remove hardness

    Explanation: Lime (CaO) reacts with CO2 and HCO3- to form CaCO3, reducing water hardness

20. Question 20

    Q20. The COD of a water sample is 100 mg/L. What does it indicate?

    • A) Low organic pollution
    • B) Moderate organic pollution
    • C) High organic pollution
    • D) No organic pollution

    Answer: High organic pollution

    Explanation: COD (Chemical Oxygen Demand) measures oxygen required to oxidize organic matter; 100 mg/L indicates high pollution