10.3 Air Quality and Climate
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16. State the approximate percentages of the primary gases in clean, dry air.
Clean, dry air is composed of approximately 78% Nitrogen (N2), 21% Oxygen (O2), and a 1% remainder consisting of noble gases (mainly Argon) and Carbon Dioxide (CO2).
17. What is the source of carbon dioxide as an air pollutant?
The complete combustion of carbon-containing fossil fuels:
C + O2 → CO2
C + O2 → CO2
18. State the sources of carbon monoxide and particulates.
The incomplete combustion of carbon-containing fuels due to restricted oxygen supplies. Particulates are unburnt carbon (soot) fragments.
19. What are the sources of methane in the atmosphere?
The anaerobic bacterial decomposition of vegetation and organic matter, alongside digestive waste emissions from livestock farming.
20. How are oxides of nitrogen formed?
They form inside internal combustion car engines, where high operational temperatures supply enough kinetic energy to force atmospheric nitrogen and oxygen gases to react.
21. What is the source of sulfur dioxide?
The combustion of fossil fuels (such as coal or crude oil) that contain trace sulfur impurities. The sulfur reacts with oxygen to form SO2 gas.
22. Describe the adverse effect of increased carbon dioxide levels.
Enhanced concentrations intensify the greenhouse effect, magnifying global warming and accelerating global climate change.
23. Why is carbon monoxide considered a pollutant?
It is a highly toxic, odorless gas that binds irreversibly to hemoglobin in blood cells, blocking internal oxygen transport.
24. What are the health risks associated with particulates?
Inhaled microparticles settle deep within lung tissues, increasing the long-term risk of respiratory diseases, asthma, and lung cancer.
25. Describe the adverse effect of increased methane levels.
Methane is a highly potent greenhouse gas that heavily contributes to global warming and subsequent disruptive climate changes.
26. What are the three adverse effects of oxides of nitrogen?
They contribute to the formation of acid rain, generate photochemical smog, and cause respiratory irritation.
27. State the adverse effect of sulfur dioxide.
It dissolves readily in atmospheric moisture to form sulfurous acid, leading directly to acid rain that damages buildings and ecosystems.
28. Explain how greenhouse gases like carbon dioxide and methane cause global warming.
The earth's surface absorbs solar radiation and re-radiates it as longer-wavelength infrared (thermal) radiation. Greenhouse gas molecules absorb this outgoing thermal energy and re-emit it in all directions, trapping heat within the atmosphere and reducing energy loss to space.
29. List five strategies to reduce the effects of climate change.
1. Planting trees (afforestation) to maximize CO2 absorption.
2. Reducing livestock farming to curb methane emissions.
3. Decreasing fossil fuel usage.
4. Expanding hydrogen infrastructure as a clean fuel alternative.
5. Accelerating reliance on renewable energy infrastructure (e.g., wind and solar power).
2. Reducing livestock farming to curb methane emissions.
3. Decreasing fossil fuel usage.
4. Expanding hydrogen infrastructure as a clean fuel alternative.
5. Accelerating reliance on renewable energy infrastructure (e.g., wind and solar power).
30. List three strategies to reduce the effects of acid rain.
1. Installing catalytic converters in passenger cars.
2. Switching to low-sulfur or ultra-low-sulfur fuels.
3. Flue gas desulfurization in industrial chimneys using calcium oxide (lime) to neutralize SO2 before release.
2. Switching to low-sulfur or ultra-low-sulfur fuels.
3. Flue gas desulfurization in industrial chimneys using calcium oxide (lime) to neutralize SO2 before release.
31. Define photosynthesis.
The endothermic chemical reaction between carbon dioxide and water to synthesize glucose and oxygen within plant leaves, utilizing solar energy captured by chlorophyll.
32. State the word equation for photosynthesis.
carbon dioxide + water → glucose + oxygen
33. State the symbol equation for photosynthesis.
6CO2 + 6H2O → C6H12O6 + 6O2
34. How do oxides of nitrogen form in car engines?
Under extreme thermal conditions inside running engines, non-metal elements from incoming air break down and react:
N2(g) + O2(g) → 2NO(g)
N2(g) + O2(g) → 2NO(g)
35. Describe how catalytic converters remove pollutants from car exhausts.
Exhaust gas passes through a hot, platinum-coated honeycomb matrix where toxic carbon monoxide and nitrogen monoxide molecules participate in a redox reaction, converting them into harmless nitrogen and carbon dioxide.
36. State the symbol equation for the reaction occurring in a catalytic converter.
2CO(g) + 2NO(g) → 2CO2(g) + N2(g)