Which of the following is a secondary pollutant?
- A.Carbon monoxide
- B.Smog
- C.Carbon dioxide
- D.Fly ash
Correct answer
Explanation
The correct answer is B, smog. A primary pollutant is released directly from a source, while a secondary pollutant is formed in the atmosphere when primary pollutants react. Photochemical smog is formed when sunlight acts on nitrogen oxides and volatile organic compounds to produce ozone and other irritants, so it is the classic secondary pollutant, and ground level ozone is counted with it. Option A is wrong because carbon monoxide comes straight out of an engine or a stove when fuel burns without enough oxygen. Option C is wrong because carbon dioxide is released directly by combustion and respiration. Option D is wrong because fly ash is the fine particulate matter that leaves the chimney of a thermal power station and is emitted as it is. The same distinction applies to acid rain, where sulphuric and nitric acids are secondary products formed from the primary gases sulphur dioxide and nitrogen oxides.
Read the full article: Ozone Layer and Acid Rain: Causes, Effects, Treaties
Practice Questions
View allWhich of the following statements about ozone is true?
- A.All of the options
- B.Ozone is highly reactive
- C.Ozone protects us from the harmful UV radiation of the sun
- D.Ozone is the major constituent of photochemical smog
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Each of the other three statements is correct on its own, which is exactly why the combined option is the answer.
Read the full explanation →Which one of the following is NOT a greenhouse gas found naturally in the atmosphere?
- A.Nitrogen oxide
- B.Carbon dioxide
- C.Methane
- D.Ozone
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Nitric oxide and nitrogen dioxide, together written as nitrogen oxides, are air pollutants that come mainly from combustion in vehicles and power stations; they help form smog and acid rain but are not counted among the greenhouse gases of the natural atmosphere.
Read the full explanation →The ozone layer that protects the earth from ultraviolet radiation lies in which layer of the atmosphere?
- A.Troposphere
- B.Stratosphere
- C.Mesosphere
- D.Thermosphere
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About nine tenths of the atmosphere's ozone lies in the stratosphere, roughly fifteen to thirty five kilometres above the surface, where ultraviolet rays split oxygen molecules and the free atoms combine with other oxygen molecules to make ozone.
Read the full explanation →The thickness of the ozone column in the atmosphere is measured in which unit?
- A.Dobson unit
- B.Curie
- C.Decibel
- D.Angstrom
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The Dobson unit, named after the scientist who built the instrument for measuring atmospheric ozone, expresses how thick the ozone column would be if all of it were brought down to the surface at standard temperature and pressure; a hundred Dobson units correspond to a layer one millimetre thick.
Read the full explanation →The Montreal Protocol, adopted in 1987, deals with which of the following?
- A.Reduction of greenhouse gas emissions
- B.Substances that deplete the ozone layer
- C.Transboundary movement of hazardous waste
- D.Conservation of wetlands
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The Montreal Protocol was adopted in 1987 under the Vienna Convention of 1985 and sets the timetable by which countries must stop producing and using chlorofluorocarbons, halons, carbon tetrachloride, methyl chloroform and methyl bromide.
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