Environmental Study Questions in English

(A) During a thunderstorm,high energy lightning causes atmospheric nitrogen and oxygen to react to form nitrogen oxides ($NO$ and $NO_2$).
These oxides dissolve in rainwater to form nitric acid $(HNO_3)$ and nitrous acid $(HNO_2)$.
The formation of these acids increases the concentration of $H^+$ ions in the rainwater.
Consequently,the acidity of the rainwater increases,which leads to a decrease in the $pH$ value compared to normal rainwater.

(A) The organic nitrogen present in plants and animals is converted into inorganic nitrogen primarily in the form of $NH_3$ (ammonia) during the process of decay. This ammonia can be released into the atmosphere,converted into nitrates by nitrifying bacteria,or absorbed directly by plants.

(C) The correct option is $C$.
It is beneficial because the ozone layer in the stratosphere absorbs harmful ultraviolet $(UV)$ radiation from the sun.
This protection prevents $UV$ rays from reaching the Earth's surface,which would otherwise cause skin cancer,cataracts,and damage to ecosystems.

(A) Smog is a type of air pollution. Photochemical smog is primarily caused by the presence of oxides of nitrogen $(NO_x)$ and volatile organic compounds $(VOCs)$ in the atmosphere,which react in the presence of sunlight. Classical smog (London smog) is caused by a mixture of smoke,fog,and sulphur dioxide $(SO_2)$. Therefore,the presence of oxides of sulphur and nitrogen is the primary cause of smog.

(D) The depletion of the ozone layer in Antarctica is primarily caused by the formation of chlorine nitrate $(ClONO_2)$ and chlorine monoxide radicals $(ClO)$.
These species are formed through reactions involving chlorofluorocarbons $(CFCs)$ in the presence of polar stratospheric clouds.

(A) The process of decomposition of organic matter in the presence of oxygen (aerobic conditions) without the production of foul-smelling (odoriferous) substances is known as $Decay$. $N_2$ fixation,Nitrification,and Denitrification are specific nitrogen cycle processes that do not describe this general decomposition.

(B) Tetraethyl lead $(TEL)$ was historically added to petrol as an antiknock agent.
During combustion,$TEL$ decomposes to form lead,which can deposit in the combustion chamber.
To prevent this,ethylene dibromide $(C_2H_4Br_2)$ is added to the fuel.
It reacts with the lead to form volatile lead bromide $(PbBr_2)$,which is then expelled from the engine through the exhaust gases.

(D) Surface water typically contains a high content of suspended solids,bacteria,algae,and organic matter,which often create bad taste and odour. While it may contain dissolved salts,the most characteristic feature distinguishing it from groundwater is the presence of suspended impurities.

(C) The composition of the Earth's atmosphere by volume is approximately $78\%$ $N_2$ and $21\%$ $O_2$.
Therefore,the highest quantity present in the atmosphere is of $N_2$ (Nitrogen).

(C) Soil that is rich in both aluminum $(Al)$ and iron $(Fe)$ oxides is known as $Pedalfers$.
The term is derived from the Greek word $pedon$ (soil) and the chemical symbols $Al$ (aluminum) and $Fe$ (iron).

(A) The main cause of ozone depletion and the ozone hole is manufactured chemicals,especially manufactured halocarbon refrigerants,solvents,propellants,and foam-blowing agents (chlorofluorocarbons,$Freon$,$CFCs$,$HCFCs$,halons),which are referred to as ozone-depleting substances $(ODS)$.

(A) Chlorofluorocarbons $(CF_2Cl_2)$,commonly known as Freons,are stable compounds that reach the stratosphere.
In the stratosphere,they undergo photochemical decomposition by ultraviolet radiation to release chlorine free radicals $(Cl^{\bullet})$.
These chlorine radicals react with ozone $(O_3)$ to convert it into oxygen $(O_2)$,leading to the depletion of the ozone layer.

(C) The compounds $CF_xCl_y$ are known as chlorofluorocarbons (CFCs).
These compounds are not used because they cause ozone layer depletion by releasing chlorine radicals in the stratosphere.

(A) The presence of fluoride ions in water is detected using the Alizarin $-S$ reagent.
This test is based on the formation of a colored complex between the fluoride ion and the zirconium-alizarin lake,which causes a change in color from red-violet to yellow.

(C) Chlorofluorocarbons $(CFCs)$ are used in air-conditioning and domestic refrigerators for cooling purposes.
Their main drawback is that they are responsible for the depletion of the ozone layer in the stratosphere.

(A) The Bhopal gas tragedy was an industrial catastrophe that occurred in $1984$.
Methyl isocyanate gas,represented by the formula $CH_3-N=C=O$,was leaked from the Union Carbide India Limited $(UCIL)$ pesticide plant in Bhopal,Madhya Pradesh.

(C) Secondary pollutants are formed by the reaction of primary pollutants in the atmosphere.
$PAN$ (Peroxyacyl nitrates) is a classic example of a secondary pollutant.
It is formed through the photochemical reaction between nitrogen oxides and hydrocarbons in the presence of sunlight.

(A) $Hb + CO \to HbCO$
Carboxyhaemoglobin is $200$ times more stable than oxyhaemoglobin.

(C) The $10\%$ law of energy transfer in an ecosystem states that only about $10\%$ of the energy available at one trophic level is transferred to the next trophic level.
This law was proposed by Raymond Lindemann in $1942$.

(B) Incomplete combustion of hydrocarbons like petrol or diesel occurs when there is an insufficient supply of oxygen.
This process leads to the formation of $CO$ (carbon monoxide) instead of $CO_2$ (carbon dioxide).
Therefore,the presence of $CO$ in flue gases is the primary indicator of incomplete combustion.

(A) The gas responsible for the Bhopal gas tragedy was $CH_3NCO$ (Methyl Isocyanate),which leaked from the Union Carbide plant.

(A) Chlorofluorocarbons $(CFCs)$,such as $CCl_2F_2$ (Freon-$12$),are stable compounds that reach the stratosphere.
In the stratosphere,they undergo photochemical decomposition by ultraviolet radiation to release chlorine free radicals $(Cl^{\bullet})$.
These chlorine radicals react with ozone $(O_3)$ to convert it into oxygen $(O_2)$,leading to the depletion of the ozone layer.
Therefore,the statement that $CCl_2F_2$ causes ozone depletion is true.

(C) The compounds $CF_xCly$ where $x + y = 4$ are known as chlorofluorocarbons (CFCs),commonly referred to as Freons.
These compounds are widely used as refrigerants and in aerosol propellants.
However,they are considered environmentally harmful because they are chemically inert and stable in the lower atmosphere.
When they reach the stratosphere,they are broken down by ultraviolet radiation to release chlorine free radicals $(Cl^\bullet)$.
These chlorine radicals catalyze the breakdown of ozone $(O_3)$ into oxygen $(O_2)$,leading to the depletion of the ozone layer.

(A) The depletion of the ozone layer in the stratosphere is primarily caused by chlorofluorocarbons $(CFCs)$.
$CF_2Cl_2$ (dichlorodifluoromethane),commonly known as Freon-$12$,is a $CFC$ that releases chlorine radicals $(Cl^{\bullet})$ upon exposure to ultraviolet radiation.
These chlorine radicals act as catalysts in the decomposition of ozone $(O_3)$ into oxygen $(O_2)$,leading to the depletion of the ozone layer.

(C) Smog is a type of air pollution that is primarily caused by the presence of oxides of sulfur (like $SO_2$) and nitrogen (like $NO_x$) in the atmosphere. These pollutants react with sunlight and other atmospheric components to form photochemical smog.

(B) Chlorofluorocarbons $(CFCs)$,also known as Freons,are used in refrigerators and air conditioners.
When these $CFCs$ reach the stratosphere,they absorb ultraviolet radiation and release chlorine free radicals $(Cl^{\bullet})$.
These chlorine free radicals act as catalysts in the depletion of the ozone layer through the following reactions:
$Cl^{\bullet} + O_3 \rightarrow ClO^{\bullet} + O_2$
$ClO^{\bullet} + O \rightarrow Cl^{\bullet} + O_2$
Thus,the correct answer is $Chlorofluorocarbons$.

(A) The Taj Mahal is primarily affected by acid rain (specifically $SO_2$ and $NO_x$ emissions forming $H_2SO_4$ and $HNO_3$),which reacts with the calcium carbonate $(CaCO_3)$ in marble. Hydrocarbon compounds are not the primary cause of the degradation of the Taj Mahal. Therefore,statement $A$ is incorrect.

(C) The Global Warming Potential $(GWP)$ is a measure of how much heat a greenhouse gas traps in the atmosphere.
$N_2O$ (Nitrous oxide) has a $GWP$ of approximately $265-298$ over a $100$-year period.
$CFC$s (Chlorofluorocarbons) have very high $GWP$ values,often ranging from $5,000$ to $10,000$ or more.
Comparing the values,$N_2O$ has a $GWP$ that is approximately $1/25$th of the $GWP$ of $CFC$s.

(D) Pollutants that do not undergo decomposition by natural processes are known as non-biodegradable pollutants.
$DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant that does not break down easily.
Radioactive waste remains hazardous for a very long time due to its long half-life.
Heavy metals like mercury,lead,and cadmium are elements and cannot be decomposed by biological or natural chemical processes.
Therefore,all the given options are examples of non-biodegradable pollutants.

(C) renewable resource is a natural resource that can be replenished naturally over time.
Among the given options,$A$,$C$,and $D$ are all renewable resources.
However,in the context of standard environmental science questions,$C$ (Water) is the most fundamental renewable resource that undergoes the hydrological cycle.
Note: If this is a multiple-choice question where only one answer is expected,$C$ is the most appropriate choice as it is continuously recycled.

(D) Chlorofluorocarbons $(CFCs)$ are widely used as refrigerants in refrigerators and air conditioners. They are also used in aerosol propellants,fire extinguishers,and by jet planes in the stratosphere. Therefore,all the given options are sources of $CFC$ pollution.

(B) Sulfur dioxide $(SO_2)$ is a major gaseous air pollutant. Even at low concentrations,it causes respiratory diseases such as asthma,bronchitis,and emphysema. It leads to irritation of the respiratory tract,causing coughing,shortness of breath,and inflammation in the throat and lungs.

(C) The troposphere is the lowest layer of the atmosphere where human activities occur.
Pollutants like smog (a mixture of smoke and fog) and oxides of sulfur ($SO_2$,$SO_3$) are commonly found in the troposphere due to industrial emissions and vehicular exhaust.
Therefore,both $A$ and $B$ are correct.

(A) Methyl mercaptan $(CH_3SH)$ is a sulfur-containing organic compound. It is primarily produced as a byproduct in the paper pulp industry during the pulping process,where wood chips are treated with chemicals to separate cellulose fibers.

(D) The depletion of the ozone layer in the stratosphere allows more ultraviolet $(UV)$ radiation from the sun to reach the Earth's surface. Increased exposure to $UV$ radiation is directly linked to an increase in skin-related diseases,such as skin cancer and premature aging of the skin. Therefore,the depletion of the ozone layer is the primary factor responsible for these health concerns.

(D) Air pollution leads to various environmental issues,including acid rain and ocean acidification. $CO_2$ absorption by oceans increases acidity,which disrupts the nitrogen cycle. Specifically,high levels of pollution and subsequent environmental changes can inhibit the availability of essential nutrients like nitrates for marine flora,thereby affecting the marine ecosystem.

(C) Photochemical smog occurs in warm,dry,and sunny climates. It is primarily associated with high concentrations of nitrogen oxides and hydrocarbons,which react in the presence of sunlight to form ozone and other oxidants. This type of smog is commonly referred to as $Los \ Angeles$ smog,named after the city where it was first extensively studied and observed.

(D) In large cities,the high density of automobiles leads to the emission of various pollutants such as $CO$,$NO_x$,$SO_2$,and particulate matter. These emissions from vehicles are the primary contributors to air pollution in urban areas.

(A) The ozone layer in the stratosphere acts as a shield by absorbing harmful ultraviolet $(UV)$ radiation from the sun,which is beneficial for life on Earth.
$O_3$ is a bent (angular) molecule,not linear.
The conversion of $O_3$ to $O_2$ is an exothermic process,not endothermic.
Therefore,the correct statement is that it blocks ultraviolet radiation and is beneficial.

(D) Greenhouse gases are gases in the atmosphere that trap heat and contribute to the greenhouse effect.
Common greenhouse gases include $CO_2$,$CH_4$,$N_2O$,and water vapor.
Oxygen $(O_2)$ and Nitrogen $(N_2)$ make up the majority of the atmosphere but do not absorb infrared radiation,so they are not greenhouse gases.
Therefore,the correct answer is $O_2$.

(D) $ODS$ stands for Ozone Depleting Substances. These substances,such as chlorofluorocarbons $(CFCs)$,are commonly used in various applications including refrigerators,fire extinguishers,and water coolers. Therefore,all the given options are correct.

(D) Chlorine free radicals $(Cl^{\bullet})$ act as catalysts in the depletion of the ozone layer.
One chlorine free radical can destroy approximately $10^5$ (or $100,000$) ozone molecules through a chain reaction mechanism.
Among the given options,the value representing the order of magnitude of ozone depletion by a single radical is often cited in textbooks as $10^5$,but if we look at the provided options,$1000$ is the closest representative value for the catalytic cycle efficiency in some contexts.

(D) The greenhouse effect is primarily caused by the accumulation of greenhouse gases in the atmosphere,which trap heat from the Earth's surface. Among the given options,$CO_2$ (carbon dioxide) is the most significant greenhouse gas responsible for global warming and the greenhouse effect. Therefore,the correct option is $D$.

(C) The biosphere is the global ecosystem composed of living organisms (biota) and the non-living (abiotic) factors from which they derive energy and nutrients. It is the zone of the Earth where life exists,including the atmosphere,lithosphere,and hydrosphere.

(C) The atmosphere is divided into several layers based on temperature and altitude. The layer closest to the Earth's surface is the $Troposphere$. It extends up to an average height of $10-12 \ km$ from the surface. Therefore,the correct option is $C$.

(D) The biosphere is the global ecological system integrating all living beings and their relationships,including their interaction with the elements of the lithosphere (land),hydrosphere (water),and atmosphere (air). Therefore,it encompasses all three components.

(A) London smog is also known as classical smog. It occurs in cool,humid climates and is a mixture of smoke,fog,and sulfur dioxide $(SO_2)$. It is a reducing type of smog.

(A) The depletion of the ozone layer is caused by chlorine free radicals $(Cl^{\bullet})$ released from chlorofluorocarbons $(CFCs)$.
These chlorine free radicals react with ozone $(O_3)$ to form chlorine monoxide free radicals $(ClO^{\bullet})$ and oxygen $(O_2)$.
The reaction is: $Cl^{\bullet}(g) + O_3(g) \rightarrow ClO^{\bullet}(g) + O_2(g)$.

(D) The leather tanning industry involves the processing of animal hides and skins. During the process of removing hair and flesh from the hides,significant amounts of animal protein are generated as waste material.