(Environmental Chemistry I: Atmosphere) KPK Class 10 Chemistry Notes Chapter #14 shrot question and long question.
Table of Contents
Short Questions Chemistry Notes Chapter #14 – The Atmosphere
Q.1) How ozone layer is depleted in the atmosphere?
Answer: Things that lead to the destruction of the ozone gas in the ozone layer depletion are the production and emission of chlorofluorocarbons. This leads to almost 80% of total ozone depletion. Besides this many other substances which lead to ozone layer depletion are hydrochlorofluorocarbons and volatile organic compounds. These substances are found in vehicular exhaust emissions, by-products of industrial processes, aerosols, and refrigerants. Ozone depletion reaction mechanism: Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3 beaking off a chlorine atom and leaving CFCl2. The chlorine atom attacks an ozone molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2). The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2. Once free the chlorine atom is off to attack another ozone molecule and begin the cycle again. CCl3F + UV →Cl + CCl2F Cl + O3 → ClO + O2 OCl. → O. + Cl. O. + O. → O2 Ozone depletion due to NOx: The different types of oxides of nitrogen found in the atmosphere are nitric oxide (NO), nitrous oxide (N2O) and nitrogen dioxide (NO2). These oxides can react with the ozone molecule and cause its depletion. hv NO → NO. NO. + O3 → NO2 + O2 Ozone depletion due to nascent oxygen: Nascent or atomic oxygen is formed by the following reaction. hv O2 → O + O This nascent oxygen produced consumes about 18% of the ozone. Ozone depletion due to SOx: Sulphur dioxide (SO2) and sulphur trioxide (SO3) are present in the atmosphere. SO2 undergoes photochemical reaction with O3 and causes it to dissociate as follows: hv SO2 → SO2. SO2. + O3 → SO3 + O2
Q.2) Differentiate between primary and secondary pollutants. Write the name and sources of greenhouse gases to the atmosphere.
Primary pollutants are substances which released directly into the air or directly produced from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulphur dioxide released from factories
Secondary pollutants are not produced directly. Secondary pollutants are formed from the primary pollutants. They are formed in the air when the primary pollutants react or interact with each other or with other substances.
Major primary pollutants produced by human activities include sulphur oxides (SOx), nitrogen oxides (NOx), Carbon dioxide (CO2) and volatile organic compounds.
An important example of secondary pollutants is ground-level ozone, which is one of the many secondary pollutants that make up the photochemical smog.
Major Greenhouse Gases. Many GHGs, including water vapor (the most important), ozone, carbon dioxide, methane, and nitrous oxide, are naturally present in the atmosphere. Other GHGs are synthetic chemicals that are emitted only as a result of human activity. 1. Water Vapour: The atmospheric concentration of water vapor is highly variable and depends largely on temperature. Water vapor is a highly active component of climate system that responds rapidly to changes in conditions by either condensing into rain or snow or evaporating to return to the atmosphere. 2. Carbon dioxide: The natural sources of CO2 are animal and plant respiration, decomposition of organic matter, forest fires and emission from volcanic eruptions. 3. Methane: Volatile organic compounds such as methane produced by wetlands are the largest natural source. They contribute to 78% of natural methane in the environment. Animals like cows, sheep, and goats during their normal digestion process produce large amounts of methane. Termites also contribute methane to the environment. 4. Nitrous Oxides: The main source of oxides of nitrogen is automobiles exhausts, industrial activities, furnaces, thermal power generations, jet airplanes, etc. 5. Ozone: Ozone is formed naturally by chemical reactions involving solar ultraviolet radiation and oxygen molecules, which make up 21 % of the atmosphere. UV 3O2 →2O3
10th Chemistry Chapter-14 (The Atmosphere)
Q.3) Define environmental chemistry and atmosphere.
Answer: Environmental chemistry: The branch of chemistry that deals with the components of the environment and the impact of human and natural factors on it is called Environmental chemistry. Of particular significance are the adverse effects of chemicals and toxic substances on human beings, plants, and animals. It plays an important role in the improvement and protection of the environment, habitats, plant and animal life, etc. Atmosphere: Atmosphere is the envelope of different gases around the Earth. It extends continuously from the Earth’s surface outwards without any boundary. About 99% of atmospheric mass lies within 30 kilometers of the surface and 75% lies within the lowest 11 kilometers.
Q.4) Sketch and briefly discuss the composition of atmosphere, by mentioning the percentage of each component. *
Answer: Composition of atmosphere: The composition of the atmosphere is variable. It changes according to time and place. The atmosphere is the mixture of different types of gases, including water vapors and dust particles. Nitrogen and oxygen are the two main gases of the atmosphere. 99% of the atmosphere is made up of these gases. Other gases like argon, carbon dioxide, hydrogen, neon, helium, etc, from the remaining part of the atmosphere. The mass of the atmosphere is approximately 4.5 to 5 x 10 15 metric tonnes, the density of the atmosphere is 0.0013 g/cm3, which gradually decrease with altitude. The details of different gases of the atmosphere are given in the table.
Q.5) How the acid rain affect the building material or statues?
Answer: Acid rain is formed when rainwater dissolves acidic air pollutants such as sulphur dioxide and nitrogen dioxide. Rainwater converts SO2 into H2SO4 and NOx to HNO2 and HNO3. Normal rainwater is weakly acidic because it has dissolved CO2 of the air. Its pH is about 5.6 to 6. But rainwater when dissolves air pollutants become acidic with pH 4. Acid deposition causes deterioration of buildings and monuments. Many of these are built of marble and limestone, which contain calcium carbonate. The acid rain attacks the calcium carbonate and turns it to calcium sulphate. The calcium sulphate is soluble in water and can be washed away. Thus, these buildings are getting dull and eroded day by day. CaCO3 + H2SO4 → CaSO4 + CO2 + H2O The deformation of historical statues in Italy and Greece were reported to be because of acid rain. In India, the Taj Mahal also faces this problem at present.
Q.6) Increase in concentration of CO2 cause greenhouse effect, justify it.
Answer: Carbon dioxide (CO2) gas forms a layer around the Earth like an envelope. It allows the light rays of Sun to pass through it and reach the Earth. These rays are reflected by the Earth’s surface and are sent back to the upper atmosphere. Normal concentration of CO2 retains enough heat to keep the atmosphere warm. CO2 is an essential gas for plants. Plants consume CO2 in the photosynthesis process and produce O2. But increasing concentration of CO2 is alarming. CO2 acts as a glass wall of a greenhouse around the Earth. It allows the light rays of Sun to pass through it and reach the Earth. The Earth’s surface absorbs some of this energy and heats up. It cools down by giving off a different form of energy, called infrared radiation. But before all this radiation can escape to outer space, the increased concentration of CO2 in the atmosphere absorbs some of it, which makes the atmosphere warmer. Thus CO2 prevents heat energy from escaping from the atmosphere. As the concentration of CO2 in air increases, less heat energy is lost from Earth’s surface. Thus, CO2 is responsible for heating up the atmosphere. This is called the greenhouse effect. Greater is amount of CO2, more is trapping of heat. This phenomenon is also called global warming.
Free Chemistry Notes For 10th Class
Q.7) Briefly discuss how the acid rain affects the aquatic life.
Answer: Effect on aquatic life: The wildlife, aquatic life, and other microorganisms are very sensitive to acidity. At pH -5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Even if a species of fish or animal can tolerate moderately acidic water but the animals they eat are not available for food. So acid rain largely affects aquatic life. For example, frog can tolerate the conditions at around pH-4 but the Mayflies they eat are more sensitive and may not survive below pH-5.6.
Q.8) List the sources which produce CO and CO2 to the atmosphere.
Answer: Sources of CO and CO2 production: Carbon Monoxide: The natural source of this gas is not very large. A very small amount of this gas is produced in – volcanic eruptions – decomposition of organic compounds – electrical discharge during storms – seed germination – natural gas emission Carbon dioxide: The natural sources of CO2 are – plant and animal respiration – decomposition of organic matter – forest fires – emission from volcanic eruptions
Q.9) What are the adverse effects of global warming?
Answer: Effects of Global Warming: Global warming is damaging the Earth’s climate as well as the physical environment. Global warming is harming the environment in several ways: 1. Desertification: Increase in temperature around the world changes the water cycle and rainfall patterns which causes desertification of certain areas. 2. Increased melting of snow and ice: Snow and ice are melting at a faster pace due to the rise in temperature. More than a million square miles of sea ice has misplaced in recent few years. 3. Sea level rise: Increase in average temperature cause ocean waters to expand on one hand and accelerates the melting of ice and glaciers on another hand and thus raises the sea level. 4. Stronger storms and cyclones: Global warming also increases the frequency of strong cyclones. Increase in temperature above the sea surface results in the increase of frequency of storms.
Q.10) What is the importance of ozone?
Answer: Importance of Ozone: The stratosphere of earth’s atmosphere contains a significant amount of O3. Thus, this gaseous compound protects living organisms including humans from harmful UV radiations. Excessive exposure to UV radiation for a longer period of time can cause melanoma or skin cancer in humans. Overall excessive UV radiation is a threat to any living organism. Hence, it is essential to maintain the ozone layer.
Q.1 a) Sketch and identify the different layers of atmosphere.
Answer: Layers of Atmosphere:
Q.1 b) Differentiate between stratosphere and troposphere?
The second layer of atmosphere which is above the troposphere is called stratosphere
The first layer of the atmosphere which is closet to the surface of the earth is called troposphere.
It starts at the top of the troposphere and extends from 11km to 50km above sea level.
The average height of this layer from the earth surface is about 11 km. It heights depend upon the latitudes, seasons and pressure.
The ozone is produced in this region when the oxygen molecule absorbs ultraviolet radiation and decompose to give atomic oxygen which immediately reacts with another O2 molecule and results in the formation of ozone molecule.
All weather phenomena like cloud formation, winds, rainfall, snowfall takes place in this region.
Weather balloons and jet aircraft fly in this region as the air present in this layer is very thin.
Almost all the dust particles and water vapours are present in this layer.
Temperature range in Celsius is -56 to-2oC
Temperature range in Celsius is 15 to -56oC
Q.2 a) Air is polluted in the big cities of Pakistan, Justify the statement.
Answer: Air pollution is the basic problem of today’s world. In Pakistan most of the big cities have crossed the permissible level of pollution. Clean air is a serious problem in Pakistan and especially in big and congested cities. In big cities beside industrial pollution, auto exhaust is the most common air polluting agent. The auto exhaust emission is directly contributing to the air pollution. It is not the duty of government to control it but every citizen also should make serious efforts to control the auto exhaust emissions. On the government part, it is suggested that it should formulate short and long term planning to reduce the auto exhaust emission problems in big cities. Because without a healthy environment there will be no healthy nation.
Q.2 b) Enlist the main sources of air pollution.
Answer: Sources of air pollution: i. Particulates ii. Oxides of carbon (Carbon monoxide and carbon dioxide) iii. Oxides of Nitrogen (NOx) iv. Sulphur Oxides (SOx) v. Volatile Organic compounds vi. CFCs ( Chloro-Flouro carbons)
Q.2 c) Prove that the oxides of nitrogen and sulphur causes air pollution.
Answer: Oxides of nitrogen and sulphur are primary pollutants and released directly into air or directly produced from a process and cause air pollution. Oxides of nitrogen react with other pollutants and oxygen to form ozone which makeup the photochemical smog; makes the air hazy and difficult to see through. Oxides of sulphur cause respiratory problems, irritation of eyes, nose and throat, pneumonia, asthma, severe headache etc.
Q.2 d) Enlist the effects of air pollution.
Answer: Effects of Air Pollution: There are various effects of air pollution some of them are: i. Respiratory and heart problems: The effects of air pollution are alarming. Air pollution causes several respiratory and heart conditions along with cancer among other treats to the body. Children who are exposed to air pollution suffer from pneumonia and asthma. ii. Global Warming: Another adverse effect of air pollution is global warming. Due to increase in temperature worldwide, the sea level is rising and melting of ice from colder regions and icebergs, displacement and loss of habitat have already signaled an impending disaster. iii. Acid Rain: Harmful gases like nitrogen oxides and sulphur oxides are released into the atmosphere during the burning of fossil fuels. When it rains the water droplets combine with these air pollutants become acidic and then falls on the ground in the form of acid rain. iv. Effects on Wild Life: Like humans animals also face some devastating effects of air pollution. Because of the presence of toxic chemicals in the air can force wildlife species to move a new place and change their habitat. v. Eutrophication: Eutrophication is a condition where a high amount of nitrogen present in some pollutants gets developed on sea’s surface and turns itself into algae and adversely affect aquatic life. vi Depletion of the ozone layer: The ozone layer is depleting due to the presence of chlorofluorocarbons in the atmosphere. As the ozone layer will do thin, it will emit harmful rays back on earth and cause skin and eye-related problems.
Q.3 a) What would be the result if rainwater is acidic?
Answer: If the rain water is acidic it would lead to weathering of buildings and sculptures as well as other things made of limestone and marbles. Plants are also damaged by acid rain. Acid rain removes minerals and nutrients from the soil that plants and trees need to grow. It increases the acidity of soil and thus affects the growth of plants. Acid rain mainly cause damage to lungs, skin and hair in human beings. The heavy metals released by acid may also cause potential threat to human health.
Q.3 b) What could be done to minimize the formation of acid rain?
Answer: Following measures can be taken to control acid rain: i. Reduce amount of sulphur dioxide and oxides of nitrogen released in the atmosphere ii. Use cleaner fuels iii. Reducing the effects of Acid Rain by Liming. iv. Use other sources of electricity (i.e. nuclear power, hydroelectricity, wind energy, geothermal energy, and solar energy). v. Flue Gas Desulphurisation (FGD)
Q.3 c) Write down the effects of acid rain on, i) Humans ii) Plants iii) Soil iv) Materials
Answer: i) Humans: The acid rain mainly causes damage in lungs, skin, and hair in human beings. The heavy metals released by acid may also cause a potential threat to human health. Acid rain also increases the acidity of water which gives rise to waterborne diseases. ii) Plants: Plants are damaged by acid rain. Acid rain removes minerals and nutrients from the soil that plants and trees need to grow. The young plants especially the newly growing buds and tips are very sensitive to acid rain. At high altitudes, acidic fog and clouds decrease nutrients from trees and plants leaving them brown or dead leaves and needles. These trees are then unable to absorb sunlight which makes them weak and unable to survive at freezing temperatures. iii) Soil: The acid rain increases the acidity of soil and thus affects the growth of plants. iv) Materials: Acid rain cause wide-ranging damage to buildings and sculptures as well as other things made of limestone and marbles such as, CaCO3 +H2SO4 → CaSO4 + CO2 + H2O The calcium sulphate is soluble in water and washed away with rainwater. The deformation of historical statues in Greece and Italy and the Taj Mahal in India were reported to be eaten away and damaged due to acid rain. The acidic particles corrode metals and cause paint and stone to deteriorate more quickly.
Q.4 a) Explain ozone layer depletion.
Answer: Ozone depletion: Ozone depletion is the decrease in concentration of ozone in stratosphere. It is also defined as the formation of hole in ozone layer. Scientific evidence shows that ozone in stratosphere is being destroyed by a number of manufactured chemicals, containing chlorine or bromine. These chemicals are referred to as ozone-depleting substances (ODS). ODS is very stable, non-toxic and environmentally safe in the lower atmosphere. This stability allows them to go up to the stratosphere intact. When reached there, they are broken apart by the ultraviolet light to release chlorine and bromine. Chlorine and bromine destroy ozone at an alarming rate, by stripping an atom from the ozone molecule. For example, Chlorofluorocarbons escape and slowly diffuse into stratosphere. Strong UV light breaks apart CFCs molecule producing chlorine-free radicals. hv CFCl3 → CFCl2 + Cl. These free radicals are very reactive. They react with ozone to form chlorine monoxide and molecular oxygen. O3 + Cl. → O2 + OCl. OCl. → O. + Cl. O. + O. → O2 In this way, a single chlorine free radical destroy thousands of ozone molecules because, after each cycle, Cl radical is free to attack another ozone molecule.
Ozone depletion due to NOx The different types of oxides of nitrogen found in the atmosphere are nitric oxide (NO), nitrous oxide (N2O) and nitrogen dioxide (NO2). These oxides can react with the ozone molecule and cause its depletion. hv NO → NO. NO. + O3 → NO2 + O2 Ozone depletion due to nascent oxygen Nascent or atomic oxygen is formed by the following reaction. hv O2 → O + O This nascent oxygen produced consumes about 18% of the ozone. Ozone depletion due to SOx Sulphur dioxide (SO2) and sulphur trioxide (SO3) are present in the atmosphere. SO2 undergoes photochemical reaction with O3 and causes it to dissociate as follows: hv SO2 → SO2. SO2. + O3 → SO3 + O2
Q.4 b) Where does ozone layer lie in the atmosphere.
Answer: Ozone layer is present in the lower part of the stratosphere also called ozonosphere. In the stratosphere its concentration reaches to maximum concentration of 10 ppm (parts per million).
Q.4 c) What evidence can you find that depletion of ozone occurs in the atmosphere?
Answer: The following evidence proves that depletion of ozone occurs in the atmosphere: – Ozone layer thickness declined, and the Antarctic ozone hole grew substantially from the 1980s through to the early 2000s. – Ozone layer depletion increases the amount of ultraviolet (UV) irradiation that reaches Earth’s surface; this can increase the risk of skin cancer, particularly at higher latitudes
Q.4 d) Recommend few ways to protect the ozone layer.
Answer: To protect the ozone layer following measures should be taken: – Buying and using recycled products – Saving of energy – Using public transport can do a lot in combating ozone layer depletion.
Q.5 a) Summarize the components of stratosphere and troposphere.
Answer: Components of Troposphere: 70 to 75% of the atmospheric gases are present in this layer. Major components of troposphere are N2, O2, CO2, and H2O. Almost all of the dust particles and water vapours are present in this layer. Components of Stratosphere: The major component of stratosphere is ozone O3. Ozone absorbs UV-radiation and protect us from harmful effects of ultraviolet radiations from the sun.
Q.5 b) Describe ozone formation.
Answer: Ozone Formation: Ozone is formed naturally by chemical reaction involving solar ultraviolet radiation (sunlight) and oxygen molecules, which make up 21% of the atmosphere. 3O2 →2O3 The formation of ozone occurs in two steps: i. In the first step: Solar ultraviolet radiation breaks apart one oxygen molecule to produce two highly reactive oxygen atoms UV O2 → 2O. ii. In second step: Each of these highly reactive atoms combines with an oxygen molecule to produce an ozone molecule. These reactions occur continuously whenever ultraviolet radiation is present in the stratosphere. As a result, the largest ozone production occurs in the stratosphere region of the atmosphere. UV O2+ O. → O3
Q.5 c) Greenhouse effects is good or bad for us, explain.
Answer: The greenhouse effect is a naturally occurring process. Without the greenhouse effect, life on the earth would be probably not possible as the average temperature of the earth would be about -18 oC rather than the present 15 oC. The natural greenhouse effect maintains the earth’s temperature at a safe level making it possible for humans and many other life forms to exist in this regard the greenhouse effect is good for us. However, the human activities have significantly enhanced the greenhouse effect causing the earth’s average temperature to rise. This is the cause of global warming, in this regard the green house effect is bad for us.
Q.5 d) Predict the outcomes of global warming.
Answer: Outcomes of Global Warming: Global warming is damaging the Earth’s climate as well as physical environment. Global warming is harming the environment in several ways including: i. Desertification: Increase in temperature around the world changes the water cycle and rainfall patterns which causes desertification of certain areas. ii. Increased melting of snow and ice: Snow and ice are melting at a faster pace due to the rise in temperature. More than a million square miles of sea ice has misplaced in recent few years. iii. Sea level rise: Increase in average temperature cause ocean waters to expand on one hand and accelerates the melting of ice and glaciers on another hand and thus raises the sea level. iv. Stronger storms and cyclones: Global warming also increases the frequency of strong cyclones. Increase in the temperature above the sea surface results in the increase of frequency of storms.