X Chemistry Model Question Test # 6 Chapter 5 Environmental chemistry Part I; The Atmosphere
Short Questions
Q1. Enlist major air pollutants and their sources
Q2. What is the cause of acid rain?
Or
How acid rain is formed? Explain.
Q3. Justify that green house effect leads to global warming.
Q4. List down the layers of atmosphere.
OR
Justify that change in altitude change the temperature of atmosphere.
Q5. Write down the effects of acid rain.
Q6. What are primary and secondary air pollutants.
Or
Give difference between primary and secondary air pollutants.
Q7. What are the sources of CO2 and CO?
Q8. How is ozone is formed in stratosphere? Explain.
Q9. How ozone layer is depleted? Explain.
Q10. What are the after effects of ozone layer depletion?
Q11. Identify as primary or secondary air pollutant SO2, CH4, HNO3, NH3, H2SO4, O3
Detailed Questions
Q1. Define atmosphere and explain its composition.
Q2. Differentiate between stratosphere and troposphere.
Q3.Describe that how different air pollutants effects environment and human health.
Q4. Describe global warming.
Q1. Enlist major air pollutants and their sources.
Answer
Some Major Pollutants and their effects on Environment & Human Health
The important pollutant are listed below
(i) Carbon monoxide (CO)………….. automobiles, fires, & industrial operations by Combustion of fossil fuels
(ii) Nitrogen dioxides (NO2)……… emissions from automobiles, electrical generation, & industrial operations.
(iii) Sulfur dioxide (SO2)…………Electricity generation, automotive emissions by fossil-fuel burning, industrial activities
(iv) Green house gases (CO2, CH4).. automotive emissions by fossil-fuel burning & industrial operations
(iv) Ozone (O3)………………………….. Oxides of Nitrogen (NO & NO2), Volatile Organic Compounds VOC’s from industrial and car emissions, gasoline vapours, chemical solvents, and electrical utilities are all sources of ozone.
(v)Particulate matter………………. Fires smokestacks, building sites, and unpaved roads are example of primary particle sources. Interactions between gaseous compounds released by power plants and cars are examples of secondary, particle sources.
(v) Lead (Pb)…………………………… metal processing, garbage incineration (burning), and fossil-fuel burning.
Q2.What is the cause of acid rain? Or How acid rain is formed? Explain.
Answer
Acid rain is one of the consequences of air pollution. Acid rain is formed on dissolving acidic gaseous air pollutants like sulphur dioxide and nitrogen oxides in the environment by the rainwater resulting in the formation sulphuric acid and nitric acid, which causes its decreasing pH value.
Details of formation of Acid Rain
The burning of fossil fuels produces oxides of sulphur and nitrogen (SO2, NO, NO2) into the atmosphere. Rainwater converts SO2 into H2SO4 and oxides of nitrogen i.e. NO and NO2 into HNO2 and HNO3 respectively. Rainwater is weakly acidic due to dissolved CO2 of the air having a pH of 5.6 to 6. Rainwater becomes more acidic and its pH reduced to 4 on dissolving air pollutants (i.e. acids).
Q4. Justify that green house effect leads to global warming. OR What are the effects of global warming?
Answer
The quantity of CO2 in the air has a direct relationship with this warming effect. The greater the amount of CO2, the greater the heat trapping or warming. This phenomenon is also known as global warming because of the increased temperature.
Primary greenhouse gases in the earth’s atmosphere are
(i) Water vapours
(ii) CO2
(iii) CH4
(iv) N2O
(v) Ozone
Effect of Global Warming/ Consequences (Effects) of increased Green House Effect
Prolonged warming of earth may produce following effects:
1. Rising Atmospheric Temperature
The accumulation of carbon dioxide in the atmosphere causes an annual increase in atmospheric temperature of roughly 0.05 degree Celsius.
2. More Frequent and Extreme Climatic Changes/ Ecological changes
Rising oceans and extreme climatic changes will change the natural environment and habitat of animals and plants. More frequent and extreme weather changes such as floods, cyclones have been predicted. It has been producing significant shift in weather patterns. Extreme weather events are occurring more frequently and with more intensity than in the past.
3. Rapid Melting of Ice and Rising Sea-Levels
Increase in temperature of earth melts glaciers and snow-caps resulting in a rise in sea levels increasing the danger of flooding and intensifying tropical cyclones. This could bring vast areas of land under sea water. As the sea level rises, low-lying regions are more likely to be submerged, rendering previously populous places uninhabitable.
Q4. List down the layers of atmosphere.
Answer
Depending upon the temperature variation and density with respect to earth surface, The Earth’s atmosphere is divided up into following 5 major layers (starting from the ground to upward):
1. Troposphere; extends upto 0 to 12 km, temperature decreases from 15°C to –56°C
2. Stratosphere; extends upto 12 to 50 km, temperature increases from –56°C to 2°C
3. Mesosphere; extends upto 50 to 85 km, temperature decreases from 2°C to –93°C
4. Thermosphere; extends upto 85 to 120 km, temperature increases from –93°C onward
5. Exosphere; extends beyond 1000 km
1. Troposphere
The lowest layer of Earth's atmosphere extending upto 12 km where temperature decreases and ranges from 15°C to –56°C is called troposphere. It is the lowest point on the earth’s surface. The bottom of the troposphere is at Earth's surface. Most of the mass (75%) of the atmosphere is in the troposphere.
2. Stratosphere
The uppermost and second layer of the atmosphere after the troposphere as we go upward is the stratosphere extending upto 50 km where temperature rises upto 2°C. It lies above the troposphere and is separated from it by Tropopause.
3. Mesosphere
Beyond the stratosphere lies the mesosphere covering upto 85 km where temperature decreases down to –93°C.
4. Thermosphere
Thermosphere is the next layer after stratosphere extending upto 120 km in which temperature goes on increasing upwards
Q5. Write down the effects of acid rain.
Answer
Harmful Effects of Acid Rain
Acid rain causing harm to soil, animals, plants and aquatic life.
(i) Effects on Buildings and Monuments
Acid rain attacks and eats away the calcium carbonate present in the marble and limestone of many buildings and monuments. Consequently, these structures are getting increasingly dull and degraded day by day.
(ii) Effects on Aquatic Life
Acid rain on soil and rocks leaches heavy metals (AI, Hg, Pb, Cr, etc.) and discharges them into rivers and lakes. Humans consumes this water as a source of drinking water. These metals accumulate in human body to a toxic level.
On the other hand, the aquatic life in lakes, suffers because of the high concentration of these metals. Especially, the high concentration of aluminum ions clogs the fish gills. It causes suffocation and ultimately death of fish.
3. Effects on Trees and Plants
Acid rain directly damages the trees and plant leaves, limiting their growth. Plants development may hampered depending on the severity of the damage. Plants’ capacity to withstand cold or illnesses deteriorates, and they eventually perish.
4. Effect on Soil
Acid rain increases the acidity of the soil. Many crops and plants cannot grow properly in such acidic soil. It also increases the levels of toxic metals in the soil, which damage the plants. The acidity of the soil, even affects old trees. Their growth is retarded becoming dry and die.
Q6. What are primary and secondary air pollutants. Or Give difference between primary and secondary air pollutants
Answer
Primary Pollutants Vs Secondary Pollutants
Primary pollutants are the waste or exhaust products driven out because of the combustion of fossil fuels and organic materials. These are the oxides of sulphur (CO2, SO3), oxides of carbon (CO, CO2), Oxides of Nitrogen (especially nitric oxide NO and nitrogen dioxide, NO2), hydrocarbons or green house gases like CH4, Ammonia (NH3) and Fluorine compounds (CFCs)
Secondary pollutants are produced from various reaction of Primary pollutants together through a variety of processes. They include Sulphuric acid, Nitric acid, Carbonic acid, Hydrofluoric acid, Ozone and Peroxy acetyl nitrate (PAN)
Q7.What are the sources of CO2 and CO?
Answer
Both of these gases emitted due to volcanic eruption and decomposition of organic matter naturally. The major sources of emission of these gases are their emissions from automobiles, fires, and industrial operations by the combustion of fossil fuels (coal, petroleum and natural gas). Fossil fuels are burnt in combustion engine of any type of automobile, kiln of any industry or open-air fires emit CO2 and CO.
Forest fires and burning of wood also emit CO2 and CO. Emission of CO dominates when supply of oxygen is limited.
Q8. How is ozone is formed in stratosphere? Explain.
Answer
Ozone Formation
The interaction of solar ultraviolet (UV) light with molecular oxygen produces stratospheric ozone (O3).
Photochemical interactions between two primary groups of air pollutants, volatile organic compounds (VOC) and nitrogen oxides, produce tropospheric or ground-level ozone, in which humans breathe.
Details of Ozone formation
The stratosphere is the atmospheric region next to troposphere and extends up to 50 km. This region has different temperatures, which increases gradually upto 2°C as altitude increases ranging lower layer temperature of about −58°C and upper layer temperature of about 2°C. The rise of temperature in stratosphere is due to the presence of ozone, which absorbs ultraviolet radiations of the Sun.
In the upper stratospheric layer, ozone is decomposed by high-energy ultraviolet radiations from the Sun, into monoatomic oxygen (O) and diatomic oxygen (O2) by high-energy ultraviolet radiations of the Sun.
In the mid stratospheric region where less UV light passes through, monoatomic O and O2 recombine to form ozone resulting in the formation of ozone layer, which is an exothermic reaction. Thus, ozone layer exists in mid stratosphere.
The lower stratosphere receives very low UV radiations, thus monoatomic oxygen is not found here and ozone is not formed here.
Under normal conditions, ozone concentration in stratosphere remains nearly constant through a series of complex atmospheric reactions involving formation and decomposition of ozone. These two reaction maintain a balance in ozone concentration.
Q9. How ozone layer is depleted? Explain.
Answer
Ozone Depletion
Ozone concentration in the stratosphere is essentially constant under normal conditions due to a series of complicated atmospheric interactions. Ozone layer is being depleted through various chemical reactions. The ozone hole is a location where the ozone layer is depleted.
For example
Chlorofluorocarbons (CFCs), which are utilized as refrigerants in air conditioner and refrigerators, are a major cause of ozone depletion. These substances leak in some way and escape into the stratosphere. The ultraviolet radiations break C-Cl bond in CFCI3 and generates highly reactive chlorine free radical. These chlorine free radicals being hyper-reactive, react with ozone to produce oxygen in the following ways:
A single chlorine free radical released by the decomposition of CFCs is capable of destroying millions of ozone molecules resulting in ozone depletion. The first sign of ozone depletion were seen over Antarctica in the 1980’s. Depletion has also been seen in the Arctic during the 1990’s.
Q10. What are the after effects of ozone layer depletion?
Answer
Effect of Ozone Layer Depletion
Even minor ozone depletion issues can have major effects.
1. Ozone depletion enables UV radiations of the Sun to reach the Earth, which can cause skin cancer in humans and other animals.
2. Decreased or thinned ozone layer will increase infectious diseases like Malaria.
3. It can change plant life cycles by disrupting the food chain.
4. It can change the wind patterns, resulting in global climate shifts. Especially, Asia and the Pacific, will be the most affected regions, facing climate induced human migration crisis.
Q11. Identify as primary or secondary air pollutant SO2, CH4, HNO3, NH3, H2SO4, O3
Answer
Primary Air Pollutants;…………… SO2, CH4, NH3
Secondary air Pollutants;………... HNO3, H2SO4, O3
Detailed Questions
Q1. Define atmosphere and explain its composition.
Answer
Composition of Atmosphere
The compositions of the atmosphere is variable and it changes according to time and place. The atmosphere is the mixture of different types of gases including water vapours and dust particles. Nitrogen and oxygen are the two main gases of the atmosphere and together constitute 99% of the atmosphere. Other gases like argon, neon, helium, hydrogen and carbon dioxide form the remaining 1% of the atmosphere.
Mass of the atmosphere ……….. 4.5 x 1015 metric tonnes
Density of the atmosphere ……... 0.0013 g/cm3 (gradually decrease with altitude)
Atmosphere is made up of
(i) 78.09 % Nitrogen (N2)
(ii) 20.95 % Oxygen (O2)
(iii) 0.93 % Argon (Ar)
(iv) 0.03 % Carbon dioxide (CO2)
(v) Inert gases like helium (0.0005%), neon (0.0018%), argon (0.93%), krypton, xenon
(vi) Water vapours (0.0 to 4) and other gases (like H).
(vii) Solid particulates including ash, dust, volcanic ash, etc. in small amounts (important in making clouds and fog)
Q2. Differentiate between stratosphere and troposphere.
Answer
Difference between Troposphere and Stratosphere
Q3. Describe that how different air pollutants effects environment and human health.
Answer
Carbon monoxide (CO)
Environmental Risk
It causes the production of smog, which adversely affects the Air Quality Index.
Human Health Risk
(i) In healthy persons, it can increase symptoms of cardiac disease, such as chest discomfort.
(ii) It can also cause visual difficulties and diminish physical and mental skills.
Nitrogen Oxides (NO and NO2)
Environmental Risk
It causes harm to the plants and favours the conditions of pollution.
Human Health Risk
It causes inflammation and irritation of the respiratory track of humans.
Sulfur Dioxide (SO2)
Environmental Risk
SO2 is the key contributor to the creation of acid rain, which destroys flora, buildings, and monuments.
It interacts to generate particulate matter.
Human Health Risk
Having trouble breathing, especially to persons having asthma or heart problems.
Ozone (O3)
Environmental Risk
It interferes with certain plants capacity to breathe, making them more vulnerable to other environment stresses (e.g., disease, harsh weather).
Human Health Risk
(i) It causes Lung function to be impaired (weakened).
(ii) It causes breathing passageways to be irritated and inflamed.
Particulate Matter
Environmental Risk
These contributes to the creation of haze and acid rain, which alters the pH balance of streams and harm vegetation, buildings and monuments.
Human Health Risk
It causes breathing passage discomfort, asthma and irregular heartbeat.
Lead (Pb)
Environmental Risk
Lead pollution causes biodiversity loss, causes reduced reproduction, and creates neurological difficulties in vertebrates.
Human Health Risk
It can have negative effects on numerous body systems and can lead to learning problems in young children.
Adults get cardiovascular consequences due to lead pollution.
Q4. Describe global warming.
Answer
Factor Disturbing natural Equilibrium between CO2 and O2
The natural equilibrium between important atmospheric gases is disturbed, because of various human activities releasing more and more CO2 into the air
Despite the fact that CO2 is not a harmful gas, its rising concentration as a result of the combustion of fossil fuels in various human activities is concerning. CO2 in the atmosphere works as a greenhouse’s glass wall.
It permits Ultra Violet and Infrared radiations to pass through, but not the other way around. Some of the infrared light released by the Earth is trapped by it.
Effect of Rising Concentration of CO2 in the Atmosphere
Due to rising concentration of CO2 in the atmosphere, some amount of heat energy is retained in the atmosphere and less thermal energy is lost from the earth surface, resulting in progressive rise in the surface’s average temperature producing a warming effect on the earth, which is known as Green House Effect. As result, higher CO2 concentration absorbs infrared radiation generated by the Earth’s surface, preventing heat energy from exiting the atmosphere. It aids in preventing the surface from cooling down at night.
Relation Between Concentration of CO2 and Warming effect (GHE)
The quantity of CO2 in the air has a direct relationship with this warming effect. The greater the amount of CO2, the greater the heat trapping or warming. This phenomenon is also known as global warming because of the increased temperature.
Primary greenhouse gases in the earth’s atmosphere are
(i) Water vapours
(ii) CO2
(iii) CH4
(iv) N2O
(v) Ozone
Effect of Global Warming/ Consequences (Effects) of increased Green House Effect
Prolonged warming of earth may produce following effects:
1. Rising Atmospheric Temperature
The accumulation of carbon dioxide in the atmosphere causes an annual increase in atmospheric temperature of roughly 0.05 degree Celsius.
2. More Frequent and Extreme Climatic Changes/ Ecological changes
Rising oceans and extreme climatic changes will change the natural environment and habitat of animals and plants. More frequent and extreme weather changes such as floods, cyclones have been predicted. It has been producing significant shift in weather patterns. Extreme weather events are occurring more frequently and with more intensity than in the past.
3. Rapid Melting of Ice and Rising Sea-Levels
Increase in temperature of earth melts glaciers and snow-caps resulting in a rise in sea levels increasing the danger of flooding and intensifying tropical cyclones. This could bring vast areas of land under sea water. As the sea level rises, low-lying regions are more likely to be submerged, rendering previously populous places uninhabitable.
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