Environmental Study Questions in English

(C) Gypsum $(CaSO_4 \cdot 2H_2O)$ is a significant non-biodegradable solid waste byproduct generated during the production of phosphate fertilizers.

(D) . Ocean acts as a major sink for $CO_2$ through physical and biological processes. This statement is correct.
$B$. The greenhouse effect leads to the warming of the earth's surface,not cooling. This statement is incorrect.
$C$. Catalytic converters are used in automobiles to convert harmful $CO$ and unburnt hydrocarbons into less harmful $CO_2$ and $H_2O$. This statement is correct.
$D$. $H_2SO_4$ mist is formed by the oxidation of $SO_2$ in the atmosphere,but herbicides and insecticides are generally classified as particulate pollutants or pesticides,not specifically as mist. Therefore,$A$ and $C$ are the correct statements.

(B) The air pollutant $SO_2$ (sulfur dioxide) is known to cause damage to plants.
High concentrations of $SO_2$ lead to the stiffness of flower buds,which eventually fall off from the plant.
This is a characteristic symptom of $SO_2$ toxicity in vegetation.

(A) The ozone layer is depleted by substances that release reactive radicals like $Cl^{\bullet}$ or $NO^{\bullet}$ in the stratosphere.
$CFCl_3$ (a chlorofluorocarbon) releases $Cl^{\bullet}$ radicals.
$NO$ (nitric oxide) reacts with ozone to form $NO_2$ and $O_2$.
$Cl_2$ can also lead to the formation of chlorine radicals.
$CH_4$ (methane) is not responsible for ozone depletion; in fact,it reacts with chlorine radicals $(Cl^{\bullet} + CH_4 \rightarrow CH_3^{\bullet} + HCl)$ and helps in removing them from the stratosphere,thereby acting as a sink for chlorine radicals.

(C) Photochemical smog is formed by the action of sunlight on nitrogen oxides $(NO_x)$ and hydrocarbons $(VOCs)$ in the atmosphere.
It is an oxidizing smog,whereas $SO_2$,smoke,and fog constitute classical smog (reducing smog).
Therefore,the statement that photochemical smog is a mixture of $SO_2$,smoke,and fog is incorrect.

(B) Global warming is primarily caused by the greenhouse effect,where certain gases trap heat in the Earth's atmosphere.
Among the given options,carbon dioxide $(CO_2)$ is the most significant contributor to global warming due to its high concentration and long atmospheric lifetime resulting from human activities like the burning of fossil fuels and deforestation.
Therefore,the correct option is $B$.

(B) Classical smog is a mixture of smoke,fog,and sulfur dioxide $(SO_2)$,which acts as a reducing agent. Hence,it is called reducing smog.
Photochemical smog is formed by the action of sunlight on nitrogen oxides $(NO_x)$ and hydrocarbons. Its common components include ozone $(O_3)$,nitric oxide $(NO)$,acrolein,formaldehyde $(HCHO)$,and peroxyacetyl nitrate $(PAN)$.
Classical smog components are primarily $SO_2$ and particulate matter,not $O_3, NO, HCHO$. Therefore,the statement in option $B$ is incorrect.

(B) The correct answer is $B$.
Photochemical smog is primarily composed of nitrogen oxides $(NO_x)$,volatile organic compounds $(VOCs)$,and ozone $(O_3)$,which are formed by the action of sunlight on these precursors.
It does not contain $SO_2$ as a primary component; $SO_2$ is associated with classical smog (sulfurous smog).
Option $A$ is correct as catalytic converters reduce $NO_x$ emissions.
Option $C$ is correct as $CFCs$ are responsible for ozone depletion.
Option $D$ is correct as acid rain increases the solubility of heavy metals in water pipes.

(B) Substances like chlorine,phosgene,sulphur dioxide,hydrogen sulphide,nitrogen dioxide $(NO_2)$,and ammonia may be released during industrial accidents and are known to cause irritation to the lungs.
Among the given options,$NO_2$ is a well-known lung irritant.

(B) Photochemical smog results from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and large manufacturing factories.
Photochemical smog has a high concentration of oxidizing agents and is therefore called oxidizing smog.
Peroxyacetyl nitrate $(PAN)$ is formed by hydrocarbons in polluted air and is a characteristic component of oxidizing smog.

(C) Greenhouse gases are gases in Earth's atmosphere that trap heat and energy.
These gases allow sunlight to pass through the atmosphere but prevent the heat radiated from the Earth's surface from escaping into space.
Common examples of greenhouse gases include $CO_2$,$CH_4$,$N_2O$,and water vapour.
$SO_2$ (Sulphur dioxide) is primarily responsible for air pollution and acid rain,but it is not considered a significant greenhouse gas.
Therefore,the correct option is $C$.

(B) The $Mesosphere$ is the coldest region among the layers of the atmosphere.
It is the layer present between the $Stratosphere$ and the $Thermosphere$.
It extends from approximately $50 \ km$ to $85 \ km$ above the Earth's surface.
The temperature in this region can drop as low as $-90^{\circ}C$.
Therefore,the $Mesosphere$ is the coldest layer.

(B) Global warming potential $(GWP)$ is a measure of the heat absorbed by a greenhouse gas in the atmosphere relative to $CO_2$.
The $GWP$ of $SF_6$ is approximately $22,200$ times that of $CO_2$ over a $100$-year period.
Therefore,$SF_6$ has the maximum global warming potential among the given options.

(D) The primary precursors of photochemical smog are $NO_2$ and hydrocarbons.
These react in the presence of sunlight to form secondary pollutants.
The secondary precursors (or secondary pollutants) of photochemical smog are ozone $(O_3)$ and peroxyacyl nitrates $(PAN)$.

(B) Rice is grown in flooded fields,a situation that depletes the soil of oxygen.
Soils that are anaerobic (lacking oxygen) allow the bacteria that produce methane from decomposing organic matter to thrive.
Some of this methane then bubbles to the surface,but most of it is diffused back into the atmosphere through the rice plants themselves.
Hence,rice paddy fields produce the maximum amount of methane gas into the atmosphere.
Therefore,option $(B)$ is correct.

(D) In environmental chemistry,Chemical Oxygen Demand $(COD)$ is the total amount of oxygen (in $ppm$) required to chemically oxidize all organic and inorganic pollutants in a given water sample. It is not a measure of bacteria.
Thus,option $(D)$ is incorrect.
- $NO_2$ is known to be a lung irritant.
- Municipal sewage typically has a $BOD$ (Biological Oxygen Demand) value ranging from $100-4000 \ ppm$.
- The primary source of $CO$ (carbon monoxide) in the atmosphere is automobile exhaust fumes.

(A) Acid rain is primarily caused by the emission of sulphur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$,specifically nitrogen dioxide $(NO_2)$.
These gases react with water vapor,oxygen,and other chemicals in the atmosphere to form sulphuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
These acids then fall to the ground as acid rain.

(D) Greenhouse gases in Earth's atmosphere include water vapour,$CO_2$,methane $(CH_4)$,nitrous oxide $(N_2O)$,and ozone $(O_3)$.
Nitrogen $(N_2)$ is the most abundant gas in the atmosphere but does not absorb infrared radiation,so it is not a greenhouse gas.

(D) Methane $(CH_4)$ in the atmosphere undergoes combustion when it reacts with oxygen $(O_2)$ present in the air. The chemical reaction is as follows:
$CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$
Therefore,the products formed are carbon dioxide $(CO_2)$ and water $(H_2O)$.

(B) Photochemical smog is formed by the action of sunlight on nitrogen oxides and hydrocarbons.
Peroxyacetyl nitrate $(PAN)$,which has the chemical formula $CH_3COONO_2$,is a major component of photochemical smog and is known to be a powerful eye irritant.

(B) $O_3$ is a strong oxidizing agent. In the atmosphere,it reacts with unburnt hydrocarbons (like methane) and other pollutants to form various compounds. Specifically,the reaction of ozone with hydrocarbons in the presence of sunlight leads to the formation of formaldehyde $(HCHO)$ and acrolein $(CH_2=CH-CHO)$.

(C) The depletion of the ozone layer is primarily caused by chlorofluorocarbons $(CFCs)$.
$1$. Reaction $II$ represents the photolysis of $CF_2Cl_2$ by $uv$ radiation to produce chlorine radicals $(\dot{Cl})$.
$2$. Reaction $IV$ shows the chlorine radical reacting with ozone $(O_3)$ to form chlorine monoxide $(Cl\dot{O})$ and oxygen $(O_2)$.
$3$. Reaction $V$ shows the chlorine monoxide radical reacting with atomic oxygen $(O)$ to regenerate the chlorine radical $(\dot{Cl})$,which continues the catalytic cycle of ozone destruction.
Therefore,reactions $II, IV,$ and $V$ are responsible for the depletion of the ozone layer.

(D) Chlorofluorocarbons (CFCs) such as $CF_2Cl_2$ (Freon-$12$),$CFCl_3$,and other halogenated compounds are responsible for ozone layer depletion.
These compounds release chlorine radicals in the stratosphere upon exposure to ultraviolet radiation:
$CF_2Cl_2 \xrightarrow{h\nu} \dot{Cl} + \dot{CF}_2Cl$
These chlorine radicals then react with ozone $(O_3)$:
$\dot{Cl} + O_3 \longrightarrow \dot{ClO} + O_2$
$\dot{ClO} + O \longrightarrow \dot{Cl} + O_2$
Thus,$CF_2Cl_2$ is the correct answer.

(A) According to the standards for drinking water quality:
$1$. The maximum prescribed concentration of $Mn$ is $0.05 \ ppm$.
$2$. The maximum prescribed concentration of $Zn$ is $5.0 \ ppm$.
$3$. The maximum prescribed concentration of $Cd$ is $0.005 \ ppm$.
$4$. The maximum prescribed concentration of $Cu$ is $3.0 \ ppm$.
Therefore,the correct matching is $A-I, B-II, C-III, D-IV$.

(A) The correct matches are as follows:
$A. Pb > 50 \ ppb$ leads to $I. \text{Liver damage}$.
$B. SO_4^{2-} > 500 \ ppm$ leads to $II. \text{Laxative effect}$.
$C. NO_3^{-} > 50 \ ppm$ leads to $III. \text{Blue baby syndrome}$.
$D. F^{-} > 2 \ ppm$ leads to $IV. \text{Brown mottling of teeth}$.
Therefore,the correct sequence is $A-I, B-II, C-III, D-IV$.

(B) The disease methemoglobinemia,also known as 'blue baby syndrome',is caused by the presence of excess nitrates $(NO_3^{-})$ in drinking water.
When ingested,nitrates are reduced to nitrites $(NO_2^{-})$ in the body,which then react with hemoglobin to form methemoglobin.
Methemoglobin is unable to transport oxygen effectively,leading to oxygen deficiency in the blood.

(D) The effects of $F^-$ ion concentration in drinking water are as follows:
$(A)$ $< 1 \ ppm$: Causes $ii$ (Tooth decay) due to lack of fluoride.
$(B)$ $> 2 \ ppm$: Causes $iii$ (Brown mottling of teeth).
$(C)$ $> 10 \ ppm$: Causes $i$ (Harmful to bones and teeth,known as fluorosis).
Therefore,the correct match is $A - ii, B - iii, C - i$.

(C) $BOD$ (Biological Oxygen Demand) is the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water at a specific temperature.
Clean water has a $BOD$ value of less than $5 \ ppm$.
Highly polluted water has a $BOD$ value of $17 \ ppm$ or more.
Therefore,the correct values are $< 5 \ ppm$ and $\geq 17 \ ppm$.

(A) The $COD$ (Chemical Oxygen Demand) is estimated by titrating a polluted water sample with a strong oxidizing agent,potassium dichromate $(K_2Cr_2O_7)$,in the presence of concentrated sulphuric acid $(H_2SO_4)$.
This process oxidizes both organic and inorganic substances present in the water sample.
$BOD$ (Biological Oxygen Demand) is measured by the amount of oxygen consumed by microorganisms over $5 \ days$,while $DO$ (Dissolved Oxygen) is measured using the Winkler method.

(C) According to the standard guidelines for drinking water quality:
$(A)$ Lead: The maximum permissible concentration is $50 \text{ ppb}$.
$(B)$ Sulphate: The maximum permissible limit is $500 \text{ ppm}$.
$(C)$ Nitrate: The maximum permissible limit is $50 \text{ ppm}$.
Therefore,the correct matching sequence is $A-III, B-I, C-II$.

(B) $BOD$ stands for $\text{Biochemical Oxygen Demand}$.
It is defined as the amount of dissolved oxygen required by aerobic microorganisms to break down the organic matter present in a given volume of water at a specific temperature over a specified time period (usually $5$ days).

(D) Statement $(i)$ is correct because $CF_2Cl_2$ (Freon-$12$) undergoes photolysis in the presence of $UV$ light to produce chlorine free radicals,which catalyze the depletion of ozone $(O_3)$ to oxygen $(O_2)$.
Statement $(ii)$ is incorrect because fluoride concentration in drinking water should be around $1 \ ppm$. Excess fluoride (e.g.,$10 \ ppm$) causes harmful effects like mottled teeth and skeletal fluorosis.
Statement $(iii)$ is correct as the maximum permissible concentration of lead in drinking water is indeed $50 \ ppb$ $(0.05 \ ppm)$.

(A) $\rightarrow IV, B$ $\rightarrow II, C$ $\rightarrow V, D$ $\rightarrow I$
$A$. Methemoglobinemia is caused by elevated levels of nitrate in drinking water ($> 50 \ ppm$ or $2000 \ ppm$ depending on the source context,here $IV$ matches).
$B$. Kidney damage is caused by the presence of $1000 \ ppb$ of lead in drinking water $(II)$.
$C$. Bones and teeth damage is caused by the presence of $50 \ ppm$ or above fluoride in drinking water $(V)$.
$D$. Growth of fish is stopped when dissolved oxygen in water is less than $1 \ ppm$ $(I)$.

(C) Methemoglobinemia,also known as blue baby syndrome,is caused by high concentrations of nitrate ions in drinking water.
When nitrate is ingested,it is reduced to nitrite in the body,which then oxidizes the iron in hemoglobin from the $Fe^{2+}$ state to the $Fe^{3+}$ state,forming methemoglobin.
Methemoglobin cannot bind oxygen effectively,leading to tissue hypoxia.
The permissible limit for nitrate in drinking water is $45 \ ppm$ or $50 \ ppm$ depending on the regulatory standard.
Therefore,the presence of excess nitrate ($X = 50 \ ppm$ of nitrate) causes this condition.

(C) ) The $BOD$ value of clean water is indeed less than $5 \ ppm$. This is a correct statement.
$b$) The Wacker process involves the oxidation of ethene to acetaldehyde $(CH_3CHO)$ in the presence of $Pd^{2+}$ and $Cu^{2+}$ catalysts,not acetic acid. Thus,this statement is incorrect.
$c$) Photochemical smog is known to cause damage to plant life,irritate eyes,and cause respiratory issues. This is a correct statement.
$d$) Reducing smog (classical smog) is a mixture of smoke,fog,and sulfur dioxide $(SO_2)$. This is a correct statement.
Therefore,statements $a, c,$ and $d$ are correct.

(D) Statement $a$ is correct: Fluoride ion concentration above $2 \ ppm$ causes brown mottling of teeth.
Statement $b$ is incorrect: The maximum limit of nitrate in drinking water is $50 \ ppm$,not $400 \ ppm$.
Statement $c$ is correct: Depletion of the ozone layer allows more $UV$ radiation to reach the Earth,which leads to cataracts and skin cancer.
Statement $d$ is incorrect: The irritant red haze in traffic is due to oxides of nitrogen $(NO_x)$,not oxides of sulphur.
Therefore,statements $a$ and $c$ are correct.

(A) The concentration of dissolved oxygen in water is essential for the survival of aquatic life.
For the healthy growth of fish,the concentration of dissolved oxygen should be approximately $6 \ ppm$.
If the concentration of dissolved oxygen falls below $6 \ ppm$,the growth of fish gets inhibited.
Therefore,the value of $X$ is $6$.

(A) The $COD$ (Chemical Oxygen Demand) is a measure of the amount of oxygen required to chemically oxidize organic matter in a water sample.
It is determined by refluxing the water sample with a known excess of potassium dichromate $(K_2Cr_2O_7)$ in the presence of concentrated sulfuric acid $(H_2SO_4)$.
The excess $K_2Cr_2O_7$ is then back-titrated with ferrous ammonium sulfate.
Therefore,the correct reagents used are $50 \% H_2SO_4$ and $K_2Cr_2O_7$.

(C) The "blue baby syndrome" (also known as methemoglobinemia) is caused by the presence of high concentrations of nitrates in drinking water.
When nitrates are ingested,they are converted into nitrites in the body,which then react with hemoglobin to form methemoglobin.
Methemoglobin is unable to transport oxygen effectively,leading to a bluish discoloration of the skin and potential health risks.

(A) Green chemistry is a way of thinking and is about utilizing the existing knowledge and principles of chemistry and other sciences to reduce the adverse impact on the environment.
It is a production process that aims to bring about minimum pollution or deterioration to the environment.
Utilizing the existing knowledge base for reducing chemical hazards along with developmental activities is the foundation of green chemistry.

(D) Green chemistry is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances.
$1$. Using soaps made of vegetable oils is an eco-friendly practice as they are biodegradable.
$2$. Using $H_2O$ for bleaching is eco-friendly as it avoids the use of harmful chlorine-based agents.
$3$. Using liquefied $CO_2$ for dry cleaning is an eco-friendly alternative to hazardous halogenated solvents.
$4$. Using plastic cans for storing substances is not considered a green chemistry practice because plastics are generally non-biodegradable and contribute to environmental pollution.
Therefore,the practice that does not come under green chemistry is $4$.

(C) Statement-$I$ is correct: Tetrachloroethene $(Cl_2C=CCl_2)$ was earlier used as a solvent for dry cleaning. It is a suspected carcinogen and contaminates groundwater. It is now replaced by liquified $CO_2$,which is environmentally friendly.
Statement-$II$ is incorrect: In the bleaching of paper and textiles,chlorine gas was used earlier,but it is now being replaced by $H_2O_2$ because $H_2O_2$ is a better bleaching agent and is more environmentally friendly.

(C) Assertion $(A)$ is correct because $CO$ is highly poisonous as it binds to haemoglobin in the blood to form carboxyhaemoglobin.
Reason $(R)$ is incorrect because the carboxyhaemoglobin complex is actually about $300$ times more stable than the oxygen-haemoglobin complex,which prevents oxygen from being transported to the tissues,leading to suffocation and death.

(A) The enamel on teeth is composed of hydroxyapatite,which is represented as $3 Ca_3(PO_4)_2 \cdot Ca(OH)_2$.
When fluoride ions $(F^-)$ are present in water or toothpaste,they react with the hydroxyapatite to form fluorapatite,which is much harder and more resistant to acid decay.
The chemical reaction is: $3 Ca_3(PO_4)_2 \cdot Ca(OH)_2 + 2 F^- \rightarrow 3 Ca_3(PO_4)_2 \cdot CaF_2 + 2 OH^-$.
Comparing this to the given formula,we identify $X = Ca(OH)_2$ and $Y = CaF_2$.

(B) Teeth enamel contains hydroxyapatite,which is $[3 Ca_3(PO_4)_2 \cdot Ca(OH)_2]$.
When it reacts with fluoride ions $(F^-)$,it is converted into fluorapatite,which is $[3 Ca_3(PO_4)_2 \cdot CaF_2]$.
This compound is much harder and more resistant to tooth decay.
The reaction is:
$[3 Ca_3(PO_4)_2 \cdot Ca(OH)_2] + 2 F^- \rightarrow [3 Ca_3(PO_4)_2 \cdot CaF_2] + 2 OH^-$

(A) Methemoglobinemia is caused by an excess of nitrate concentration in drinking water.
High levels of nitrate in drinking water can cause methemoglobinemia,which is also known as $blue \ baby \ syndrome$.
When consumed,nitrates are absorbed into the blood and some are converted into nitrites,which react with hemoglobin to create methemoglobin,reducing the oxygen-carrying capacity of the blood.

(C) Non-biodegradable wastes are substances that cannot be broken down by biological processes. Thermal power plants generate fly ash,which is a non-biodegradable waste product.

(D) In environmental chemistry,the medium or component that is adversely affected by a pollutant is known as a $receptor$ or $target$. $Receptors$ can be biotic (living organisms) or abiotic (non-living components) that suffer negative impacts due to the presence of pollutants.

(A) The thermosphere is the fourth layer of the Earth's atmosphere and is located above the mesosphere.
In this region,the air is very thin.
The thermosphere includes the ionosphere,which is a region filled with charged particles.
Due to high temperatures and solar radiation,molecules undergo ionization to form species such as $O_2^{+}$,$O^{+}$,and $NO^{+}$.