Environmental Study Questions in English

(N/A) $(1)$ Classical smog,Photochemical smog
$(2)$ Formaldehyde,Acrolein
$(3)$ Melanoma
$(4)$ Freons

(N/A) $(1)$ Polar stratospheric clouds
$(2)$ Point source
$(3)$ Non-point source
$(4)$ $10 \ ppm, 2,00,000 \ ppm$

(N/A) $(1)$ Tooth decay (dental caries)
$(2)$ $50 \ ppb$
$(3)$ $50 \ ppm$
$(4)$ Organophosphates,Carbamates

(N/A) $(1)$ Cement
$(2)$ Electricity,Fertilizer

(A) $(1)$ True: The troposphere is the lowest layer of the atmosphere where life exists.
$(2)$ False: The troposphere extends up to approximately $10 \ km$ to $12 \ km$ from sea level,not $25 \ km$.
$(3)$ True: The stratosphere is the layer above the troposphere,extending from $10 \ km$ to $50 \ km$.
$(4)$ False: The ozone layer is located in the stratosphere,not the troposphere.

(C) $(1)$ True: $NO_2$ is a respiratory irritant that can cause lung damage in children.
$(2)$ True: $CO$ binds to hemoglobin to form carboxyhemoglobin.
$(3)$ False: The carboxyhemoglobin complex is about $300$ times more stable than the oxygen-hemoglobin complex,not $100$ times.
$(4)$ True: Normal rainwater has a $pH$ of approximately $5.6$ due to the dissolution of atmospheric $CO_2$.

(N/A) $(1)$ True: Mist is formed by particles of spread liquid and by condensation of vapour in air.
$(2)$ False: Particulate matter of size up to $5 \ \mu m$ is trapped in the nasal passage,whereas particulate matter of size less than $1 \ \mu m$ reaches directly into the lungs.
$(3)$ True: Ozone and nitric oxide are known to cause irritation in the nose and throat.

(N/A) Statement $(1)$ is false. The concentration of dissolved oxygen in cold water is typically around $10 \ ppm$,not $100 \ ppm$.
Statement $(2)$ is true. If the concentration of dissolved oxygen in water is less than $6 \ ppm$,the growth of fish gets inhibited.

(A) The correct matching is as follows:
$(A)$ Smoke: Mixture of solid and liquid particles formed by combustion of organic matter $(4)$.
$(B)$ Dust: Fine solid particles $(2)$.
$(C)$ Mist: Produced by particles of spray liquids and by condensation of vapours $(3)$.
$(D)$ Fumes: Formed by condensation of vapours during chemical reactions $(1)$.
Therefore,the correct sequence is $(A-4, B-2, C-3, D-1)$.

(A-3, B-4, C-1, D-2) The correct matching is:
$A-3$: Toxic heavy metals are released by chemical factories and industries.
$B-4$: Pesticides are substances used to kill insects,fungi,and weeds.
$C-1$: Sediments result from soil erosion due to agricultural and mineral industries.
$D-2$: Microorganisms are introduced through domestic sewage disposal.
Therefore,the correct sequence is $A-3, B-4, C-1, D-2$.

The greenhouse effect is primarily caused by the accumulation of certain gases in the atmosphere that trap heat. Their relative contributions to global warming are as follows:

\text{Gas}	\text{Contribution}
$CO_2$	$50\%$
$CH_4$	$19\%$
$CFCs$	$17\%$
$O_3$	$8\%$
$N_2O$	$4\%$
$H_2O$ (vapour)	$2\%$

(N/A) The acids present in acid rain are $H_{2}CO_{3}$,$HNO_{3}$,and $H_{2}SO_{4}$.
$H_{2}CO_{3}$ is formed when atmospheric $CO_{2}$ dissolves in the presence of water vapor:
$CO_{2} + H_{2}O \rightarrow H_{2}CO_{3}$
$HNO_{3}$ is formed from nitrogen oxides. Natural sources of $NO$ include forest fires and lightning. Anthropogenic sources include combustion in aircraft,vehicle engines,furnaces,and power plants. $NO$ reacts with air to form $NO_{2}$,which dissolves in water to form $HNO_{3}$:
$3NO_{2} + H_{2}O \rightleftharpoons 2HNO_{3} + NO$
$H_{2}SO_{4}$ is formed from sulfur oxides. Sulfur oxides are produced by the combustion of fossil fuels and the extraction of metals from sulfide ores. $SO_{2}$ reacts with oxygen and water to form $H_{2}SO_{4}$:
$2SO_{2} + O_{2} + 2H_{2}O \rightarrow 2H_{2}SO_{4}$

(N/A) Ozone present in the stratosphere of the Earth's atmosphere is a natural gift. The ozone layer extends from $20 \text{ km}$ to $35 \text{ km}$ above the Earth's surface. The ozone layer protects the Earth from harmful ultraviolet $(UV)$ rays emitted by the Sun.
$A$ depletion in the ozone layer is harmful to the entire ecosystem. $A$ $5\%$ decrease in the amount of ozone can lead to a $20\%$ increase in skin cancer cases. Ultraviolet rays are also responsible for eye diseases such as cataracts.
It causes genetic mutations and damages crops. It also harms seed-bearing plants. Ultraviolet rays also affect aquatic life and aquatic vegetation.

(N/A) Chlorofluorocarbons (CFCs),used as refrigerants and aerosol propellants,are released into the atmosphere.
In the stratosphere,they decompose in the presence of ultraviolet $(UV)$ radiation to release chlorine atoms (free radicals):
$CF_{2}Cl_{2} \xrightarrow{hv} ^{\bullet}CF_{2}Cl + Cl^{\bullet}$
These reactive chlorine atoms then react with ozone to deplete the ozone layer through the following chain reactions:
$Cl^{\bullet} + O_{3} \rightarrow ClO^{\bullet} + O_{2}$
$ClO^{\bullet} + O \rightarrow Cl^{\bullet} + O_{2}$
It is observed that a single molecule of $CFC$ can destroy up to $1000$ molecules of ozone.

(D) Industrial and domestic solid waste is generally classified into two types:
$(i)$ Biodegradable waste
$(ii)$ Non-biodegradable waste
If such waste is not disposed of properly,it accumulates in the environment.
Animals often consume this waste,especially non-biodegradable materials like polythene bags,which can cause severe health issues or even death.

(A) The condition of the pond is due to the process of $Eutrophication$.
Organic waste and detergents from household activities provide nutrients that promote the rapid growth of aquatic plants and algae.
As these organisms die,they are decomposed by bacteria,which consume the dissolved oxygen in the water.
This depletion of oxygen leads to the death of other aquatic life and the release of foul-smelling gases,rendering the water unusable.

(N/A) Biodegradable pollutants are those that can be decomposed by bacteria and other microorganisms. Examples include sewage,cow dung,fruit peels,and vegetables.
Non-biodegradable pollutants are those that cannot be decomposed by bacteria. Examples include mercury $(Hg)$,aluminum $(Al)$,copper $(Cu)$,lead $(Pb)$,and $DDT$.

(N/A) The sources of dissolved oxygen in water are as follows:
$(i)$ Photosynthesis by aquatic plants.
$(ii)$ Direct contact of the water surface with air.
$(iii)$ Mechanical aeration.

(B) Biochemical Oxygen Demand $(BOD)$ is a measure of the pollution caused by biodegradable organic matter.
These biodegradable pollutants are decomposed by bacteria,which consume dissolved oxygen in the process.
$A$ lower $BOD$ value indicates that the water contains fewer biodegradable substances,while a higher $BOD$ value indicates higher pollution levels.

(B) The excessive use of fertilizers in the surrounding areas leads to the runoff of phosphate ions into water bodies,which promotes the excessive growth of algae (algal bloom).
As these algae die and decompose,they consume dissolved oxygen,leading to a significant decrease in oxygen levels.
This depletion of dissolved oxygen is harmful to fish and other aquatic life.
Additionally,the decomposition process produces foul odors and makes the water aesthetically unpleasant,rendering it unsuitable for activities like swimming or boating.

(N/A) The symptoms observed in the villagers indicate the release of nitrogen oxides $(NO_x)$ and sulfur dioxide $(SO_2)$ from the factory chimney. These gases are produced by the combustion of fossil fuels like coal and petroleum.
In industrial processes or automobile engines,when fossil fuels are burned at high temperatures,dinitrogen and dioxygen react to form nitric oxide $(NO)$:
$N_2 + O_2 \xrightarrow{1200-1500^{\circ}C} 2NO$
$NO$ further reacts with oxygen to form nitrogen dioxide $(NO_2)$:
$2NO + O_2 \xrightarrow{1100^{\circ}C} 2NO_2$
Sulfur dioxide $(SO_2)$ is produced by the combustion of sulfur-containing fossil fuels or by the roasting of sulfide ores like iron pyrites $(FeS_2)$ or copper pyrites $(CuFeS_2)$:
$S + O_2 \rightarrow SO_2$
$2Cu_2S + 3O_2 \rightarrow 2Cu_2O + 2SO_2$

(N/A) The conversion of $SO_2$ to $SO_3$ in the atmosphere occurs through photochemical or non-photochemical processes.
$1$. Photochemical process: $SO_2$ molecules absorb light in the near-ultraviolet region and react with ozone $(O_3)$:
$SO_2 + O_3 \xrightarrow{h\nu} SO_3 + O_2$
$2SO_2 + O_2 \xrightarrow{h\nu} 2SO_3$
$2$. Non-photochemical process: In the presence of particulate matter (dust),$SO_2$ reacts with atmospheric oxygen:
$2SO_2 + O_2 \rightarrow 2SO_3$
$3$. Role of $NO_2$: In the presence of sunlight,$NO_2$ undergoes photolysis to produce $NO$ and an active oxygen atom:
$NO_2 \xrightarrow{h\nu} NO + [O]$
This highly reactive oxygen atom reacts with $O_2$ to form ozone $(O_3)$:
$O_2 + [O] + M \rightarrow O_3 + M$
(where $M$ is a third body like $N_2$ that absorbs excess energy).

(B) Photochemical smog is formed by the reaction of nitrogen oxides $(NO_x)$ and hydrocarbons in the presence of sunlight.
$1$. Nitrogen dioxide $(NO_2)$ undergoes photolysis in the presence of sunlight to produce nitric oxide $(NO)$ and atomic oxygen $(O)$: $NO_{2(g)} \xrightarrow{h\nu} NO_{(g)} + O_{(g)}$.
$2$. The highly reactive atomic oxygen then reacts with molecular oxygen $(O_2)$ in the presence of an inert gas $(M)$ to form ozone $(O_3)$: $O_{(g)} + O_{2(g)} \xrightarrow{M} O_{3(g)}$.

(A) Ozone in the stratosphere is a product of $UV$ radiation acting on dioxygen $(O_2)$.
$UV$ radiation splits the oxygen molecule into free oxygen atoms $(O)$.
These oxygen atoms then react with other oxygen molecules to form ozone $(O_3)$.
$O_{2(g)} \xrightarrow{UV} O_{(g)} + O_{(g)}$
$O_{(g)} + O_{2(g)} \rightleftharpoons O_{3(g)}$

(N/A) Ozone is continuously formed in the stratosphere by the action of $UV$ radiation on dioxygen $(O_2)$ and is simultaneously decomposed by $UV$ radiation of wavelength $240-360 \ nm$.
$O_3 \xrightarrow{240-360 \ nm} O_2 + O$
The atomic oxygen $(O)$ then reacts with $O_3$ molecules:
$O_3 + O \rightarrow 2O_2$
Thus,a dynamic equilibrium is established between the formation and decomposition of $O_3$,maintaining a constant concentration of ozone in the stratosphere rather than settling at the surface.

(N/A) In winter,special clouds called polar stratospheric clouds form over Antarctica. These clouds provide a surface for the hydrolysis of chlorine nitrate to form hypochlorous acid,and they also react with hydrogen chloride to produce chlorine molecules.
$ClONO_{2(g)} + H_2O_{(g)} \rightarrow HOCl_{(g)} + HNO_{3(g)}$
$ClONO_{2(g)} + HCl_{(g)} \rightarrow Cl_{2(g)} + HNO_{3(g)}$
When sunlight returns to Antarctica in the spring,the heat from the sun causes these clouds to break down. The sunlight then triggers the photolysis of $HOCl$ and $Cl_2$:
$HOCl_{(g)} \xrightarrow{hv} \cdot OH_{(g)} + Cl^{\bullet}_{(g)}$
$Cl_{2(g)} \xrightarrow{hv} 2Cl^{\bullet}_{(g)}$
Thus,chlorine free radicals are generated,which initiate the chain reaction for ozone depletion.

(B) If the concentration of sulfate in drinking water exceeds $500 \ ppm$,it causes a laxative effect in humans. Moderate amounts are generally harmless.

(A-4, B-5, C-2, D-1) The correct matches are: $(A-4), (B-5), (C-2), (D-1)$.
$(A)$ Acid rain is primarily caused by $SO_2$ and $NO_x$ emissions.
$(B)$ Photochemical smog is formed by the reaction of unsaturated hydrocarbons and nitrogen oxides in the presence of sunlight.
$(C)$ Carbon monoxide $(CO)$ binds strongly with hemoglobin,reducing its oxygen-carrying capacity.
$(D)$ Ozone layer depletion is caused by chlorofluorocarbons (CFCs) like $CHCl_2-CHF_2$.

(A-4, B-5, C-1, D-3, E-2) $(A-4), (B-5), (C-1), (D-3), (E-2)$
$(A)$ Oxides of sulphur cause respiratory diseases like asthma and bronchitis.
$(B)$ Nitrogen dioxide is responsible for the red haze in traffic and congested areas.
$(C)$ Increased concentration of $CO_2$ in the atmosphere is responsible for global warming.
$(D)$ High concentration of nitrate in drinking water causes methaemoglobinaemia (blue baby syndrome).
$(E)$ Lead can damage the kidney,liver,and reproductive system.

(A-5, B-4, C-1, D-2, E-3) The correct matching is: $(A-5, B-4, C-1, D-2, E-3)$.
$(A)$ Burning sulfur-containing waste leads to classical smog,acid rain,water pollution,respiratory problems,damage to buildings,and metal corrosion.
$(B)$ Use of carbonates as pesticides is associated with neurological disorders in humans.
$(C)$ Using synthetic detergents for washing clothes leads to water pollution.
$(D)$ Releasing smoke from vehicles and factories leads to photochemical smog,damage to plant life,corrosion of buildings,respiratory problems,and water pollution.
$(E)$ Using chlorofluorocarbon compounds leads to damage to the ozone layer.

(A-4, B-3, C-1, D-2) The correct matching is: $(A-4, B-3, C-1, D-2)$.
$(A)$ Phosphate fertilizers promote the growth of algae,which leads to eutrophication and increases the $BOD$ of water.
$(B)$ Methane is a greenhouse gas that contributes to global warming.
$(C)$ Synthetic detergents are non-biodegradable and increase the $BOD$ of water.
$(D)$ Nitrogen oxides react with water to form nitric acid,which causes acid rain.

(N/A) To control or reduce photochemical smog,the most direct method is to prevent the release of nitrogen oxides and hydrocarbons into the atmosphere. Methods include: $(i)$ Using high-quality catalytic converters in vehicles to convert harmful gases into harmless ones. $(ii)$ Using specific compounds that react with free radicals to prevent the formation of toxic smog components. $(iii)$ Planting trees like $Pinus$,$Juniperus$,$Pyrus$,and $Vitis$ that can metabolize nitrogen oxides.
$(b)$ Chlorinated solvents used in dry cleaning are carcinogenic. Replacing them with liquid $CO_2$ is a greener alternative. For bleaching,$H_2O_2$ is used instead of chlorine-based agents as it is effective and environmentally safe.
$(c)$ To reduce synthetic detergents,use soaps made from vegetable oils,which are biodegradable,unlike synthetic detergents.
$(d)$ Replace petrol and diesel with cleaner fuels like $CNG$,$LNG$,or hydrogen,which produce significantly less pollution.

(N/A) Carbon dioxide is a natural component of the atmosphere and is essential for all forms of plant life. It constitutes approximately $0.033 \%$ of the atmospheric volume and helps maintain the temperature necessary for life.
The concentration of $CO_{2}$ in the atmosphere is maintained because it is released during respiration,combustion of fossil fuels,and decomposition of limestone,while simultaneously being consumed by plants during photosynthesis.
However,human activities disturb this balance,leading to an increase in atmospheric $CO_{2}$ levels. This is caused by excessive use of fossil fuels,deforestation,and industrialization.
It is estimated that the concentration of $CO_{2}$ has increased by approximately $25 \%$ in the last century.
Over the last $120$ years,the Earth's temperature has risen by approximately $0.4^{\circ} C$ to $0.8^{\circ} C$.
Current estimates suggest that doubling the concentration of $CO_{2}$ will lead to a temperature increase of $1.0^{\circ} C$ to $3.5^{\circ} C$. $CO_{2}$ contributes about $50 \%$ to the greenhouse effect,while other gases contribute the remaining $50 \%$.

(N/A) Visible light from the sun reaches the Earth and warms it.
When the Earth cools down,it emits energy in the form of infrared radiation,which has a longer wavelength and heating effect.
These infrared rays are absorbed by greenhouse gases like $CO_2$ and water vapor.
This absorbed heat is radiated back to the Earth's surface,increasing the overall temperature.
If the solar energy reaching the Earth remains constant but the concentration of $CO_2$ increases,the amount of heat trapped also increases,leading to global warming.

(N/A) Pesticides applied to the crops are absorbed by the plants. When these crops are used as fish feed,the pesticides enter the fish's digestive system.
This process is known as $Biomagnification$. As the pesticides move from lower trophic levels to higher trophic levels through the food chain,their concentration increases.
Eventually,the concentration of pesticides in the fish becomes high enough to cause serious metabolic and physiological disturbances,making them unfit for human consumption.

(A) Tetrachloroethene $(Cl_2C=CCl_2)$ is a suspected carcinogen and is known to contaminate groundwater. Avoiding its use prevents these harmful effects.
However,the use of liquid $CO_2$ with detergents is not entirely environmentally friendly. Many detergents are not biodegradable and can cause water pollution. Furthermore,the release of $CO_2$ into the atmosphere contributes to the greenhouse effect.

(A) The atmosphere is composed of several gases. Nitrogen $(N_2)$ is the most abundant gas in the Earth's atmosphere. Its volume percentage is approximately $78.08\%$.

(B) Dry air is composed of several gases. By volume,the composition of dry air is approximately $78\%$ nitrogen,$21\%$ oxygen,and $1\%$ other gases (including argon,carbon dioxide,etc.).
Therefore,the percentage of oxygen by volume in dry air is $21\%$.

(N/A) The non-biodegradable detergents present in the sewage water are not completely removed during the treatment process. These detergents persist in the water and cause foaming in rivers and ponds,leading to water pollution.

(B) Soaps are sodium or potassium salts of long-chain fatty acids,which are easily broken down by microorganisms in the environment,making them biodegradable.
In contrast,synthetic detergents,especially those with highly branched hydrocarbon chains,are resistant to bacterial degradation,leading to water pollution.

(A) In refrigerators,$HFC-134a$ ($1,1,1,2$-tetrafluoroethane) is now used instead of $CFC$s because it is less harmful to the environment and does not deplete the ozone layer.

(B) Green chemistry is defined as the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.
It aims to promote sustainable development by minimizing environmental impact through efficient resource use and waste reduction.

(N/A) Chemistry is fundamental to understanding the environment as it deals with the composition,properties,and interactions of matter. It helps in studying the chemical processes occurring in the atmosphere,such as the depletion of the ozone layer,the greenhouse effect,and the formation of acid rain. Furthermore,chemistry provides solutions for environmental protection by developing eco-friendly materials,waste management techniques,and methods to monitor and control pollution.

(B) The troposphere is the lowest layer of the Earth's atmosphere,extending from the surface up to about $10-15 \ km$.
It contains the air we breathe and is where most weather phenomena occur.
It is held to the Earth's surface by gravity.

(C) The troposphere is the lowest layer of the atmosphere where we live. It is essential for our survival as it contains the air we breathe and regulates the weather patterns necessary for life.

(C) The troposphere is the lowest layer of the atmosphere. It primarily contains $N_2$ and $O_2$,along with small amounts of $CO_2$,water vapor,and other trace gases.

(B) In a thermal power station,the chemical energy (heat of combustion) of fossil fuels (coal,gas,or oil) is converted into electrical energy.
In such plants,the chemical energy of the fuel is first used to convert water into high-pressure steam.
This high-pressure steam is then used to rotate a turbine,which is connected to a generator to produce electricity.
This process is not very efficient because a significant amount of energy is lost as heat during the conversion process,resulting in an efficiency of approximately $40 \%$.
Additionally,thermal power stations are a major source of pollution due to the combustion of fossil fuels.

(D) In the stratosphere,$CFCs$ release chlorine free radicals $(Cl)$:
$CF_{2}Cl_{2(g)} \stackrel{UV}{\longrightarrow} Cl_{(g)} + CF_{2}Cl_{(g)}$
These chlorine radicals react with $O_{3}$ to form chlorine monoxide $(ClO)$ radicals,not chlorine dioxide $(ClO_{2})$ radicals.
$Cl_{(g)} + O_{3(g)} \rightarrow ClO_{(g)} + O_{2(g)}$
Therefore,the statement in option $D$ is incorrect.

(A) $(1)$ Acid rain corrodes water pipes,resulting in the leaching of heavy metals such as iron,lead,and copper into the drinking water. Thus,statement $(a)$ is correct.
$(2)$ Acid rain damages buildings and other structures made of stone or metal. Thus,statement $(b)$ is correct.
$(3)$ It causes respiratory ailments in human beings and animals. Therefore,statement $(c)$ is incorrect.
$(4)$ It is harmful for agriculture,trees,and plants as it washes down the nutrients needed for their growth. Therefore,statement $(d)$ is incorrect.
Since statements $(c)$ and $(d)$ are incorrect,the correct option is $(A)$.