Environmental Study Questions in English

(C) Thermal power plants burn fossil fuels like coal,which release oxides of sulfur $(SO_x)$ and nitrogen $(NO_x)$ into the atmosphere. These gases react with water vapor to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$,which result in acid rain.

(B) Eutrophication is the process in which nutrient-enriched water bodies support a dense plant population,such as algae.
This excessive plant growth consumes dissolved oxygen,leading to the death of aquatic animal life due to oxygen deprivation.
This process results in a significant loss of biodiversity and is a clear indicator of a polluted environment.
In contrast,a $BOD$ value of $5 \ ppm$ is considered clean,$0.03 \%$ $CO_2$ is normal atmospheric concentration,and a $pH$ of $5.6$ is the natural acidity of unpolluted rain.

(C) The presence of soluble fluoride ions in drinking water up to $1 \ ppm$ is considered safe for teeth. It helps in making the enamel on teeth much harder by converting hydroxyapatite,the enamel on the surface of the teeth,into much harder fluorapatite.

(D) The correct statement is that carboxyhaemoglobin (haemoglobin bound to $CO$) is about $300$ times more stable than oxyhaemoglobin.
Therefore,the statement that it is less stable is incorrect.

(C) Acid rain reacts with the marble $(CaCO_{3})$ of the Taj Mahal,causing damage to it.
As a result,the monument is being slowly disfigured,and the marble is becoming discoloured and lustreless.
Therefore,the statement that it causes no damage to monuments is false.

(C) Air pollution that occurs in sunlight is known as oxidizing smog (also called photochemical smog).
It is formed by the action of sunlight on nitrogen oxides and hydrocarbons.

(A) Excess nitrate in drinking water can cause methemoglobinemia,which is also known as blue baby syndrome.

(B) In the presence of ozone $(O_{3})$,oxidising smog increases during the daytime.
Automobiles and factories produce the main components of photochemical smog (oxidising smog) due to the action of sunlight on unsaturated hydrocarbons and nitrogen oxides.
Ozone is a strong oxidising agent and reacts with unburnt hydrocarbons in polluted air to produce various chemicals,thereby increasing the intensity of oxidising smog.

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

(A) Methane $(CH_4)$ contributes to global warming and is involved in the formation of photochemical smog.
Paddy fields are a significant source of methane emission due to anaerobic decomposition.
Methane has a higher global warming potential compared to $CO_2$,making it a stronger greenhouse gas.
Methane is not a component of reducing smog (which typically consists of $SO_2$ and particulate matter).
Therefore,statements $A, B,$ and $C$ are correct.

(C) Greenhouse gases are gases in the atmosphere that trap heat.
Major greenhouse gases include $CO_2$ (Carbon dioxide),$H_2O$ (Water vapour),and $CH_4$ (Methane).
Therefore,$A, C$ and $D$ are greenhouse gases.

(D) Eutrophication is the process in which nutrient-enriched water bodies support a dense plant population,which kills animal life by depriving it of oxygen and results in a loss of biodiversity.
$A$. Excess usage of fertilisers leads to nutrient enrichment (e.g.,nitrates and phosphates),causing eutrophication.
$B$. Excess usage of detergents also adds phosphates to water bodies,causing eutrophication.
$C$. Dense plant population is a result/symptom of eutrophication,not a cause.
$D$. Lack of nutrients is the opposite of the condition required for eutrophication.
Since the question asks for the incorrect reason$(s)$,both $C$ and $D$ are incorrect as causes. However,looking at the provided options,$D$ is the most fundamentally incorrect statement regarding the cause of eutrophication.

(D) Statement $I$ is true: Thermal power plants generate large amounts of fly ash,which is a non-biodegradable waste.
Statement $II$ is true: Biodegradable detergents,especially those containing phosphates,can lead to eutrophication in water bodies,which depletes dissolved oxygen and harms aquatic life.

(D) The gas $CH_4$ (methane) is released during the anaerobic degradation of vegetation. $CH_4$ is a potent greenhouse gas that contributes to global warming,and some studies suggest it may be associated with health risks,including potential carcinogenic effects in specific contexts.

(D) Statement $I$ is false. Reducing smog (classical smog) is a mixture of smoke,fog,and sulphur dioxide $(SO_2)$. It does not involve an allotrope of oxygen as an intermediate.
Statement $II$ is true. Photochemical smog is formed by the action of sunlight on nitrogen oxides $(NO_x)$ and hydrocarbons present in the troposphere. Sulphur dioxide is primarily associated with reducing smog,not photochemical smog.
Therefore,Statement $I$ is false and Statement $II$ is true.

(D) The presence of ozone in the troposphere is harmful as it acts as a pollutant and generates photochemical smog.

(C) Statement $I$ is true because $BOD$ is a measure of the amount of dissolved oxygen required by bacteria to decompose organic matter in water,which directly impacts aquatic life.
Statement $II$ is false because clean water typically has a $BOD$ value of less than $5 \ ppm$,while highly polluted water has a $BOD$ value of $17 \ ppm$ or more.
There is no single 'optimum' value of $6.5 \ ppm$ defined for $BOD$.

(D) Statement $I$ is true because normal rain water has a $pH$ of approximately $5.6$ due to the dissolution of atmospheric $CO_2$ to form weak carbonic acid $(H_2CO_3)$.
Statement $II$ is true because when the $pH$ of rain water drops below $5.6$ due to the presence of pollutants like oxides of sulfur $(SO_x)$ and nitrogen $(NO_x)$,it is termed as acid rain.
Therefore,both statements are correct.

(A) The $F^{-}$ ions make the enamel on teeth much harder by converting hydroxyapatite,$[3 Ca_{3}(PO_{4})_{2} \cdot Ca(OH)_{2}]$,which is the enamel on the surface of the teeth,into much harder fluoroapatite,$[3 Ca_{3}(PO_{4})_{2} \cdot CaF_{2}]$.
Thus,the correct formula for hydroxyapatite is $[3 Ca_{3}(PO_{4})_{2} \cdot Ca(OH)_{2}]$.

(D) Photochemical smog is an oxidizing mixture of pollutants like ozone $(O_3)$,nitric oxide $(NO)$,acrolein,formaldehyde,and peroxyacetyl nitrate $(PAN)$.
These oxidizing agents react with the double bonds in rubber,leading to its degradation and cracking.
Therefore,both Assertion $(A)$ and Reason $(R)$ are true,and $(R)$ is the correct explanation for $(A)$.

(D) In the stratosphere,$CFCs$ (like $CF_2Cl_2$) are broken down by powerful $UV$ radiations,releasing a chlorine free radical $\dot{Cl}$.
The reaction is: $CF_2Cl_{2(g)} \xrightarrow{UV} \dot{Cl}_{(g)} + \dot{CF_2}Cl_{(g)}$
Thus,the intermediates formed initially are $\dot{Cl}$ and $\dot{CF_2}Cl$.

(C) Ozone in the stratosphere is a product of $UV$ radiations acting on dioxygen $(O_2)$ molecules.
$O_{2(g)} \xrightarrow{UV} O_{(g)} + O_{(g)}$
$O_{(g)} + O_{2(g)} \xrightarrow{UV} O_{3(g)}$

(C) The $BOD$ value of clean water $(A)$ is typically less than $5 \, ppm$. So,$A < 5$.
The $BOD$ value of highly polluted water $(B)$ is generally greater than $17 \, ppm$. So,$B > 17$.
Therefore,the correct option is $C$.

(C) Wet deposition refers to the removal of pollutants from the atmosphere by rain,snow,or fog. Ammonium salts are commonly found in rain droplets,leading to wet deposition.
Dry deposition refers to the process where gases or particles settle on ground surfaces in the absence of precipitation. Oxides of nitrogen and sulphur (like $SO_2$) are acidic and settle down on ground surfaces as dry deposition.

(C) $BOD$ (Biochemical Oxygen Demand) is a measure of the amount of dissolved oxygen required by bacteria to decompose organic matter present in a water sample.
Clean water typically has a $BOD$ value of less than $5 \ ppm$,while highly polluted water has a $BOD$ value of $17 \ ppm$ or more.
Therefore,among the given options,$3 \ ppm$ represents the cleanest water sample.

(C) The correct matching is as follows:
$(a)$ $2 SO_{2(g)} + O_{2(g)} \rightarrow 2 SO_{3(g)}$ represents the formation of $SO_3$ which leads to acid rain,so $(a)-(iv)$ (as it is a part of tropospheric pollution).
$(b)$ $HOCl_{(g)} \stackrel{h \nu}{\longrightarrow} \dot{O}H + \dot{Cl}$ is a reaction involved in the depletion of the ozone layer,so $(b)-(iii)$.
$(c)$ $CaCO_{3} + H_{2}SO_{4} \rightarrow CaSO_{4} + H_{2}O + CO_{2}$ is the reaction of acid rain with marble/limestone,so $(c)-(i)$.
$(d)$ $NO_{2(g)} \stackrel{h \nu}{\longrightarrow} NO_{(g)} + O_{(g)}$ is a key step in the formation of photochemical smog,so $(d)-(ii)$.
Thus,the correct sequence is $(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)$.

(B) Green chemistry aims to reduce or eliminate the use and generation of hazardous substances.
Chlorine gas was traditionally used for bleaching paper,which is harmful to the environment.
$Tetrachloroethene$ $(Cl_{2}C=CCl_{2})$ was earlier used as a solvent for dry cleaning,but it is a suspected carcinogen and contaminates groundwater.
Liquified $CO_{2}$ is used as a safer alternative for dry cleaning,which is a classic example of green chemistry.

(C) Among the given options,$NO_{2}$ is known to retard the process of photosynthesis in plants.
High concentrations of $NO_{2}$ damage the leaves and reduce the rate of photosynthesis.

(B) Statement $I$ is false because $CFCs$ are broken down by powerful $UV$ radiation,not visible radiation,and they release chlorine free radicals,not chlorine gas.
$CF_{2}Cl_{2(g)} \xrightarrow{UV} \dot{Cl}_{(g)} + \dot{C}F_{2}Cl_{(g)}$
$\dot{Cl}_{(g)} + O_{3(g)} \rightarrow \dot{Cl}O_{(g)} + O_{2(g)}$
$\dot{Cl}O_{(g)} + O_{(g)} \rightarrow \dot{Cl}_{(g)} + O_{2(g)}$
Statement $II$ is false because atmospheric ozone reacts with nitric oxide to produce nitrogen dioxide and oxygen,not nitrogen and oxygen gases.
$NO_{(g)} + O_{3(g)} \rightarrow NO_{2(g)} + O_{2(g)}$

(C) Eutrophication is the process where nutrient enrichment leads to excessive growth of algae,which consumes dissolved oxygen during decomposition.
This process leads to a decrease in the oxygen level of water.
Therefore,the statement that eutrophication leads to an increase in the oxygen level is incorrect.

(A) Carbon monoxide $(CO)$ binds with haemoglobin in the blood to form carboxyhaemoglobin,which is more stable than oxyhaemoglobin.
$(b)$ Sulphur dioxide $(SO_2)$ causes stiffness of flower buds in plants.
$(c)$ Polychlorinated biphenyls $(PCBs)$ are known to be carcinogenic.
$(d)$ Oxides of nitrogen $(NO_x)$ are metabolized by certain plants like $Pyrus$ (pear).
Therefore,the correct matching is $(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)$.

(A) Tetrachloroethene $(Cl_{2}C=CCl_{2})$ was previously used as a solvent for dry cleaning,but it is a suspected carcinogen and pollutes groundwater.
Liquid $CO_{2}$ is now used as an environmentally friendly alternative for dry cleaning,as it is non-toxic and does not pollute the environment.

(A) The presence of particulate matter in polluted air catalyses the oxidation of sulphur dioxide to sulphur trioxide: $2SO_{2(g)} + O_{2(g)} \rightarrow 2SO_{3(g)}$.
This reaction is also promoted by ozone $(O_3)$ and hydrogen peroxide $(H_2O_2)$:
$SO_{2(g)} + O_{3(g)} \rightarrow SO_{3(g)} + O_{2(g)}$
$SO_{2(g)} + H_2O_{2(l)} \rightarrow H_2SO_{4(aq)}$
Thus,particulate matter,ozone,and hydrogen peroxide all enhance the pollution caused by oxides of sulphur.

(D) $CH_4$,$O_3$,and $H_2O$ are greenhouse gases that contribute to global warming.
$N_2$ is the most abundant gas in the atmosphere and does not absorb infrared radiation,therefore it does not contribute to the greenhouse effect.

(C) Clean water has a $BOD$ value of less than $5 \, ppm$,whereas highly polluted water has a $BOD$ value of $17 \, ppm$ or more. Therefore,Assertion $A$ is correct.
$BOD$ (Biochemical Oxygen Demand) is a measure of the amount of dissolved oxygen required by bacteria to decompose only the biodegradable organic matter present in water. It does not include non-biodegradable organic material. Therefore,Reason $R$ is incorrect.

(A) Eutrophication is the process in which nutrient enrichment (such as nitrates and phosphates) leads to excessive growth of algae and aquatic plants.
This excessive growth depletes dissolved oxygen in the water,which leads to the death of aquatic organisms and ultimately results in the loss of biodiversity.

(C) The $BOD$ (Biochemical Oxygen Demand) value is a measure of the amount of dissolved oxygen required by bacteria to decompose organic matter present in a water sample.
Clean water typically has a $BOD$ value of less than $5 \, ppm$.
Highly polluted water,which contains a significant amount of organic waste,typically has a $BOD$ value greater than $17 \, ppm$.
Comparing the given values:
$A = 3 \, ppm$ (Clean)
$B = 18 \, ppm$ (Highly polluted)
$C = 21 \, ppm$ (Highly polluted)
$D = 4 \, ppm$ (Clean)
Therefore,samples $B$ and $C$ are highly polluted.

(B) Polar stratospheric clouds provide a surface on which the hydrolysis of $ClONO_2$ takes place to form $HOCl$ (hypochlorous acid).
$ClONO_{2(g)} + H_2O_{(g)} \rightarrow HOCl_{(g)} + HNO_{3(g)}$

(A) The reactions occurring on the surface of polar stratospheric clouds are as follows:
$1$. Hydrolysis of chlorine nitrate: $ClONO_2 + H_2O \rightarrow HOCl (A) + HNO_3 (B)$
$2$. Reaction of chlorine nitrate with $HCl$: $ClONO_2 + HCl \rightarrow HNO_3 (B) + Cl_2 (C)$
Comparing these with the given options,$A = HOCl$,$B = HNO_3$,and $C = Cl_2$. Therefore,the correct option is $A$.

(A) Statement $I$ is correct: Classical smog (also known as London smog) occurs in cool,humid climates and is a reducing mixture of smoke,fog,and sulphur dioxide $(SO_2)$.
Statement $II$ is correct: Photochemical smog occurs in warm,dry,and sunny climates. Its major components include ozone $(O_3)$,nitric oxide $(NO)$,acrolein $(CH_2=CH-CHO)$,formaldehyde $(HCHO)$,and peroxyacetyl nitrate ($PAN$,$CH_3CO-O-ONO_2$).
Therefore,both statements are correct.

(D) Photochemical smog is formed by the action of sunlight on unsaturated hydrocarbons and nitrogen oxides $(NO_x)$ in the atmosphere.
It is an oxidizing type of smog,unlike classical smog which is reducing.

(D) Acid rain is primarily caused by the oxidation of $SO_{2}$ in the atmosphere in the presence of moisture and oxygen.
The overall chemical reaction is: $2 SO_{2} + O_{2} + 2 H_{2}O \rightarrow 2 H_{2}SO_{4}$.

(A) The Taj Mahal is made of marble,which is primarily calcium carbonate $(CaCO_3)$.
Acid rain contains sulfuric acid $(H_2SO_4)$,which reacts with the marble to form calcium sulfate $(CaSO_4)$,water,and carbon dioxide.
This reaction causes the surface of the marble to corrode and lose its luster.
The chemical reaction is: $CaCO_3 + H_2SO_4 \rightarrow CaSO_4 + H_2O + CO_2$.

(C) . Sulphate - $III$. Laxative effect
$B$. Fluoride - $II$. Bending of bones
$C$. Nicotine - $I$. Pesticide
$D$. Sodium arsinite - $IV$. Herbicide
Therefore,the correct matching is $A-III, B-II, C-I, D-IV$.

(C) Photochemical smog is formed by the action of sunlight on nitrogen oxides $(NO_x)$ and volatile organic compounds $(VOCs)$ such as formaldehyde $(HCHO)$.
It typically contains ozone $(O_3)$,nitrogen dioxide $(NO_2)$,nitric oxide $(NO)$,formaldehyde $(HCHO)$,acrolein,and peroxyacetyl nitrate $(PAN)$.
Sulfur dioxide $(SO_2)$ is a primary component of classical smog (London smog),not photochemical smog.

(A) The correct matching is as follows:
$A$. Microorganisms are primarily found in $II$. Domestic sewage.
$B$. Plant nutrients (like nitrates and phosphates) are commonly found in $III$. Chemical fertilizers.
$C$. Toxic heavy metals are often released by $IV$. Chemical factories.
$D$. Sediment is caused by $I$. Strip mining activities.
Therefore,the correct sequence is $A-II, B-III, C-IV, D-I$.

(A) Statement $I$: Fly ash and slag generated as waste from the steel industry are effectively utilized by the cement industry as raw materials.
Statement $II$: Fuel derived from plastic waste through processes like pyrolysis has a high octane rating and is lead-free,often referred to as green fuel.
Therefore,both Statement $I$ and Statement $II$ are correct.

(B) . Sulphate $(> 500 \ ppm)$ causes a laxative effect.
$B$. Nitrate $(> 50 \ ppm)$ causes methemoglobinemia (blue baby syndrome).
$C$. Lead $(> 50 \ ppb)$ causes kidney damage and affects $RBC$ production.
$D$. Fluoride $(> 2 \ ppm)$ causes brown mottling of teeth.
Therefore,the correct matching is $A-III, B-I, C-IV, D-II$.

(D) Statement $I$ is false because in polluted water,the value of dissolved oxygen is low,but the value of $BOD$ (Biological Oxygen Demand) is high due to the presence of organic matter that requires oxygen for decomposition.
Statement $II$ is true because eutrophication leads to the excessive growth of algae and weeds,which consume dissolved oxygen,thereby decreasing its concentration in water bodies.
Therefore,Statement $I$ is false and Statement $II$ is true.

(D) Herbicides are chemical substances used to destroy unwanted plants. $Sodium \ chlorate$ $(NaClO_3)$ and $sodium \ arsenite$ $(Na_3AsO_3)$ are both well-known examples of herbicides. $Aldrin$ and $Dieldrin$ are classified as insecticides.