Class 9 Atmospheric Pollution Mock Test (ICSE)

Topics in Atmospheric Pollution

• Acid rain: causes and effects
• Global warming and greenhouse gases
• Ozone depletion
• Control of atmospheric pollution

Atmospheric Pollution practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following chemical species is primarily responsible for the catalytic destruction of the ozone layer in the stratosphere?

   1. (a)$\text{Methane (}\text{CH}_4\text{)}$
   2. (b)$\text{Carbon dioxide (}\text{CO}_2\text{)}$
   3. (c)$\text{Chlorofluorocarbons (}\text{CFCs}\text{)}$
   4. (d)$\text{Sulphur dioxide (}\text{SO}_2\text{)}$
   Show answer and step marks

   1. Correct option: (c). Chlorofluorocarbons ($\text{CFCs}$) release active chlorine atoms in the stratosphere which catalytically break down ozone ($\text{O}_3$) molecules.+1

   Answer: (c)
2. Q2Multiple choice·1 mark
   Which of the following environmental management practices involves planting rows of trees around industrial zones or highways to absorb gaseous pollutants and act as a natural pollutant sink?

   1. (a)Flue gas desulfurization
   2. (b)Green belt development
   3. (c)Electrostatic precipitation
   4. (d)Catalytic conversion
   Show answer and step marks

   1. Correct option: (b). Green belt development is a strategy that involves planting trees around pollution sources to absorb gaseous pollutants like carbon dioxide and reduce particulate dispersion.+1

   Answer: (b)
3. Q3Multiple choice·1 mark
   Which anthropogenic greenhouse gas contributes the maximum percentage to the enhanced global warming phenomenon?

   1. (a)$\text{Water vapour (}\text{H}_2\text{O}\text{)}$
   2. (b)$\text{Ozone (}\text{O}_3\text{)}$
   3. (c)$\text{Nitrous oxide (}\text{N}_2\text{O}\text{)}$
   4. (d)$\text{Carbon dioxide (}\text{CO}_2\text{)}$
   Show answer and step marks

   1. Correct option: (d). Carbon dioxide ($\text{CO}_2$) is the primary anthropogenic greenhouse gas driving global warming.+1

   Answer: (d)
4. Q4Multiple choice·1 mark
   Which of the following pairs of gases are the primary precursors responsible for causing acid rain?

   1. (a)Hydrogen sulphide ($\text{H}_2\text{S}$) and ammonia ($\text{NH}_3$)
   2. (b)Sulphur dioxide ($\text{SO}_2$) and nitrogen dioxide ($\text{NO}_2$)
   3. (c)Carbon monoxide ($\text{CO}$) and methane ($\text{CH}_4$)
   4. (d)Chlorofluorocarbons ($\text{CFCs}$) and carbon monoxide ($\text{CO}$)
   Show answer and step marks

   1. Correct option: (b) Sulphur dioxide ($\text{SO}_2$) and nitrogen dioxide ($\text{NO}_2$). In moist air $\text{SO}_2$ dissolves to form sulphurous acid, which is oxidised to sulphuric acid, and $\text{NO}_2$ reacts with water and oxygen to form nitric acid; these acids fall as acid rain.+1

   Answer: (b)
5. Q5Short answer·2 marks
   State two harmful effects of ultraviolet radiation reaching the Earth's surface as a consequence of ozone layer depletion.
   Show answer and step marks

   1. First harmful effect, any one of: skin cancer; cataract and other eye damage; weakening of the immune system; severe sunburn; reduced photosynthesis and lower crop yields; death of phytoplankton, which harms aquatic food chains; or any other valid harmful effect of ultraviolet radiation.+1
   2. Second harmful effect, a different one from the same list.+1

   Answer: Any two of: skin cancer; cataract (eye damage); weakened immune system; sunburn; reduced photosynthesis and crop yield; death of phytoplankton harming aquatic life.
6. Q6Long answer·4 marks
   Answer the following questions regarding the control of atmospheric pollution: (a) Explain the function of a catalytic converter fitted in modern automobile exhaust systems. Name two toxic gases that are neutralized by it. [2] (b) State any two effective methods or devices used in industrial units to control air pollution, specifically mentioning how they reduce particulate matter or acidic gas emissions. [2]
   Show answer and step marks

   1. (a) Function: the catalytic converter contains catalysts such as platinum, palladium and rhodium that change toxic exhaust gases into harmless carbon dioxide, nitrogen and water vapour before they leave the exhaust.+1
   2. (a) First toxic gas, any one of: carbon monoxide ($\text{CO}$); oxides of nitrogen ($\text{NO}$, $\text{NO}_2$); unburnt hydrocarbons; or any other valid exhaust pollutant it removes.+0.5
   3. (a) Second toxic gas, a different one from the same list.+0.5
   4. (b) First method, any one of: electrostatic precipitator; wet scrubber; cyclone separator; bag (fabric) filter; or any other valid industrial control device.+0.5
   5. (b) How the first method works: an electrostatic precipitator charges dust and smoke particles and collects them on oppositely charged plates; a wet scrubber sprays water or an alkaline slurry (lime) that dissolves and neutralises acidic gases such as $\text{SO}_2$; a cyclone separator spins the gas so heavy particles are thrown out; a bag filter traps fine particles in fabric.+0.5
   6. (b) Second method, a different one from the same list.+0.5
   7. (b) How the second method works, as described above for that device.+0.5

   Answer: (a) Its catalysts (platinum, palladium, rhodium) change toxic exhaust gases into harmless carbon dioxide, nitrogen and water vapour; two of the gases removed are carbon monoxide and oxides of nitrogen (or unburnt hydrocarbons). (b) Any two of: electrostatic precipitators (charged plates collect dust and smoke); wet scrubbers (water or lime slurry dissolves and neutralises $\text{SO}_2$); cyclone separators (spinning throws out heavy particles); bag filters (fabric traps fine particles).

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