Environmental Study Questions in English

(C) Environmental pollution is defined as the effect of undesirable changes in the properties of air,land,water,or soil that may harmfully affect human life or other species. These changes are caused by the introduction of pollutants into the environment.

(B) Petroleum is a fossil fuel formed over millions of years from the remains of ancient marine organisms. Because its formation rate is extremely slow compared to its consumption rate,it is classified as a $Non-renewable$ energy source.

(C) In the atmosphere,aldehydes are produced by the reaction of oxygen atoms with hydrocarbons.

(D) The incomplete combustion of petrol in a car engine releases carbon monoxide $(CO)$.
$CO$ is a highly toxic and poisonous gas that binds to hemoglobin in the blood,preventing oxygen transport.

(C) The correct answer is $(C)$.
In the atmosphere,hydrocarbons react with oxygen atoms (often generated by the photolysis of ozone or $NO_2$) to form various oxygenated products,including aldehydes.

(D) Micro-organisms present in the soil act as a sink for $CO$ (carbon monoxide) by oxidizing it to $CO_2$.

(D) Photochemical smog is formed by the reaction of nitrogen oxides $(NO_x)$,volatile organic compounds $(VOCs)$,and sunlight.
Common components of photochemical smog include ozone $(O_3)$,acrolein $(CH_2=CH-CHO)$,formaldehyde,and peroxyacetyl nitrate $(PAN)$.
Chlorofluorocarbons $(CFCs)$ are primarily responsible for the depletion of the ozone layer in the stratosphere and are not components of photochemical smog.

(C) The correct option is $C$. The statement "When the $pH$ of rain water is higher than $6.5$,it is called acid rain" is incorrect.
Acid rain is defined as rain water having a $pH$ value less than $5.6$ due to the presence of dissolved oxides of sulfur and nitrogen.

(D) Photochemical smog is formed in warm and sunny climates during the daytime by the action of sunlight on primary pollutants like nitrogen oxides and hydrocarbons.
It contains components such as nitrogen oxides,ozone $(O_3)$,and peroxyacetyl nitrate $(PAN)$,which are oxidising in nature.
Therefore,photochemical smog is an oxidising agent in character.
It is well-known to cause irritation in the eyes and throat,making statement $D$ incorrect.

(B) The concentration of $DO$ (Dissolved Oxygen) in water is crucial for aquatic life. The growth of fish is inhibited if the concentration of $DO$ falls below $6 \ ppm$. Therefore,the statement that a concentration below $6 \ ppm$ is good for the growth of fish is false.

(D) Green chemistry refers to the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.
It aims to minimize the environmental impact of chemical production by preventing pollution at the source.
Therefore,it is an alternative tool for reducing pollution.

(D) Those pollutants which cannot be broken down into simpler,harmless substances in nature are called non-biodegradable pollutants.
$DDT$,plastics,polythene,insecticides,pesticides,mercury,lead,arsenic,metal articles,synthetic fibers,glass objects,and iron products are examples of non-biodegradable pollutants.
Therefore,$DDT$ is a non-biodegradable pollutant.

(C) The ozone layer primarily absorbs ultraviolet $(UV)$ radiation from the sun,preventing it from reaching the earth's surface. It does not block infrared radiation. Therefore,statement $C$ is incorrect. All other statements are scientifically accurate.

(A) First,convert all concentrations to $ppm$ $(1 \ ppm = 1000 \ ppb)$:
$1.$ Fluoride: $1000 \ ppb = 1 \ ppm$ (Permissible limit is $1 \ ppm$)
$2.$ Lead: $40 \ ppb = 0.04 \ ppm$ (Permissible limit is $0.05 \ ppm$)
$3.$ Nitrate: $100 \ ppm$ (Permissible limit is $45 \ ppm$)
$4.$ Iron: $0.2 \ ppm$ (Permissible limit is $0.2 \ ppm$)
The concentration of nitrate $(100 \ ppm)$ is significantly higher than the permissible limit of $45 \ ppm$. Excess nitrate in drinking water causes methemoglobinemia,also known as blue baby syndrome.

(C) According to the World Health Organization $(WHO)$ and Indian standards for drinking water,the maximum permissible concentration of fluoride $(F^-)$ is $1.0 \; ppm$. Concentrations above $2 \; ppm$ cause fluorosis (brown mottling of teeth).
The maximum permissible limit for nitrate $(NO_3^-)$ is $50 \; ppm$. Since the given concentration is $50 \; ppm$,it is at the threshold limit and generally considered acceptable.
The maximum permissible limit for sulphate $(SO_4^{2-})$ is $500 \; ppm$. Since the given concentration is $100 \; ppm$,it is well within the safe limit.
Therefore,only fluoride $(F^-)$ at $10 \; ppm$ makes the water unsuitable for drinking.

(B) Photochemical smog is formed by the action of sunlight on unsaturated hydrocarbons and nitrogen oxides.
Its primary components include ozone $(O_3)$,peroxyacetyl nitrate ($PAN$,$CH_3-C(=O)-O-O-NO_2$),and acrolein $(CH_2=CH-CHO)$.
Hydrogen gas $(H_2)$ is not a component of photochemical smog.

(D) Statement $(S_1)$ is true because $CO_2$ is a major greenhouse gas.
Statement $(S_2)$ is true because classical smog is a mixture of smoke,fog,and $SO_2$.
Statement $(S_3)$ is false because $DDT$ is a non-biodegradable pollutant.
Statement $(S_4)$ is false because clean drinking water must have a low $B.O.D.$ (Biochemical Oxygen Demand).
Therefore,the sequence is $T, T, F, F$.

(D) $1$. The statement in option $A$ is correct. Fluoride ions react with hydroxyapatite to form fluoroapatite,which is harder and more resistant to decay.
$2$. The statement in option $B$ is correct. High levels of nitrate in drinking water reduce the oxygen-carrying capacity of blood,leading to methemoglobinemia.
$3$. The statement in option $C$ is correct. Hydrogen peroxide acts as a mild bleaching agent and is commonly used in laundry for whitening clothes.
$4$. Since all the given statements are correct,the incorrect statement is 'None of these'.

(D) Biodegradability of surfactants depends on the structure of the hydrocarbon chain.
Straight-chain alkylbenzene sulfonates are more easily degraded by microorganisms than branched-chain ones.
Highly branched alkylbenzene sulfonates,such as the one shown in option $D$,are resistant to microbial attack because the branching hinders the enzymatic degradation process.
Therefore,the highly branched structure makes it the least biodegradable.

(D) Greenhouse gases $(GHGs)$ are gases that trap heat in the atmosphere,such as $CO_2$,$CH_4$,$N_2O$,$O_3$,and water vapor.
$NO$ (Nitric oxide) is not considered a greenhouse gas.
Therefore,the correct option is $D$.

(D) Photochemical smog is formed by the reaction of sunlight with nitrogen oxides $(NO_x)$ and volatile organic compounds $(VOCs)$.
Primary components include $NO$,$NO_2$,and hydrocarbons.
Secondary components include ozone $(O_3)$,peroxyacetyl nitrate ($PAN$,$CH_3-CO-O-O-NO_2$),and aldehydes like acrolein $(CH_2=CH-CHO)$.
Carbon dioxide $(CO_2)$ is a greenhouse gas but does not contribute to the formation of photochemical smog.

(B) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$ into the atmosphere,which react with water to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
Normal rain has a $pH$ of about $5.6$ due to the presence of dissolved $CO_2$,but acid rain has a $pH$ lower than $5.6$.
$CO_2$ and $CO$ are not the major contributors to acid rain; rather,$SO_2$ and $NO_x$ are the primary pollutants.
Acid rain leaches essential nutrients from the soil,affecting plant growth,and it reacts with calcium carbonate $(CaCO_3)$ in monuments like the Taj Mahal,causing discoloration and degradation.

(D) According to the standards for drinking water:
$1$. The concentration of $F^{-}$ should be up to $1 \ ppm$ to $2 \ ppm$. Concentrations above $2 \ ppm$ cause brown mottling of teeth and harmful effects on bones. Here,$[F^{-}] = 10 \ ppm$,which is much higher than the limit.
$2$. The concentration of $SO_4^{2-}$ is considered harmful if it exceeds $500 \ ppm$. Here,$[SO_4^{2-}] = 100 \ ppm$,which is within the safe limit.
$3$. The concentration of $NO_3^{-}$ is considered harmful if it exceeds $50 \ ppm$. Here,$[NO_3^{-}] = 50 \ ppm$,which is at the threshold limit but generally considered safe.
Therefore,only $F^{-}$ makes the water sample unsuitable for drinking.

(B) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$ into the atmosphere.
These gases react with water vapor in the presence of oxygen to form $H_2SO_4$ and $HNO_3$,which are strong acids.

(B) Lichens are highly sensitive to sulfur dioxide $(SO_2)$ pollution in the atmosphere. They do not grow in areas where the concentration of $SO_2$ is high. Therefore,they act as biological indicators of air pollution,specifically for $SO_2$.

(D) Anthropogenic (environmental pollution originating in human activity) sources of water pollution include domestic waste,sewage,soaps,detergents,run-off from agricultural fields having fertilizers and pesticides,industrial wastes as effluents,heat,waste from animal sheds and slaughterhouses,oil spills,etc. Since all the options listed contribute to water pollution,the correct answer is $D$.

(C) Lead $(Pb)$ is primarily released into the atmosphere through industrial processes,combustion of leaded gasoline,and waste incineration. Therefore,it is considered an air pollutant.

(C) $London$-type smog or classical smog is caused mainly by air pollution due to the combustion of coal and emission of sulphur dioxide and dust.
It is formed in the morning of winter season especially.

(A) Excess nitrate in drinking water reacts with hemoglobin to form methemoglobin,which prevents the blood from carrying oxygen effectively. This condition is known as methemoglobinemia,often referred to as the 'blue baby syndrome'.

(D) Photochemical smog is formed by the action of sunlight on nitrogen oxides and hydrocarbons.
It consists of primary pollutants like nitrogen oxides $(NO_x)$ and secondary pollutants like ozone $(O_3)$,formaldehyde,acrolein,and peroxyacetyl nitrate $(PAN)$.
Among the given options,ozone $(O_3)$ is a major component of photochemical smog.

(D) The $BOD$ (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 has a $BOD$ value of less than $5 \ ppm$.
- Moderately polluted water has a $BOD$ value between $5 \ ppm$ and $10 \ ppm$.
- Highly polluted water has a $BOD$ value of $17 \ ppm$ or more.
Since the given $BOD$ value is $20 \ ppm$,which is greater than $17 \ ppm$,the water is considered highly polluted.

(A) The reaction of $Sulphur \ dioxide$ $(SO_2)$ with water molecules present in the atmosphere forms $Sulphuric \ acid$ $(H_2SO_4)$,which leads to acid rain.
This acid rain reacts with the calcium carbonate $(CaCO_3)$ of the marble,causing decolouring,cracks,and decomposition of the monument.
The proximity of the $Mathura \ Refinery$ to the $Taj \ Mahal$ is a major source of $SO_2$ emissions.
Therefore,the correct answer is $Sulphur \ dioxide$.

(A) The $BOD$ value is a measure of the amount of dissolved oxygen required by bacteria to decompose organic matter present in a water sample.
Clean water has a $BOD$ value of less than $5 \ ppm$.
Polluted water has a $BOD$ value of $17 \ ppm$ or higher,typically considered higher than $10 \ ppm$.
Therefore,the statement that polluted water has a $BOD$ value higher than $10 \ ppm$ is correct.

(C) The marble of the Taj Mahal is primarily composed of calcium carbonate $(CaCO_3)$.
Pollutant gases like $SO_2$ and $NO_2$ react with moisture in the atmosphere to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$,respectively.
These acids cause acid rain,which reacts with the marble to form soluble salts,leading to the discolouration and loss of lustre of the monument.

(D) Greenhouse gases are those gases that absorb and emit radiation within the thermal $IR$ range.
This process is the fundamental cause of the greenhouse effect.
The primary greenhouse gases include $CO_2, CH_4, N_2O,$ and $O_3$.

(C) $BOD$ stands for Biochemical Oxygen Demand. It is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given water sample at a specific temperature over a specific time period.

(B) Liquefied $CO_2$ is considered a better strategy for dry cleaning because it is environmentally friendly and replaces the use of hazardous solvents like $Cl_2C=CCl_2$ (Tetrachloroethylene),which is a suspected carcinogen and groundwater pollutant. Therefore,$CO_2$ is the preferred choice for sustainable dry cleaning.

(C) Photochemical smog is formed by the action of sunlight on nitrogen oxides and hydrocarbons.
It consists of primary pollutants like nitrogen oxides ($NO$ and $NO_2$) and secondary pollutants such as ozone $(O_3)$,formaldehyde,acrolein,and peroxyacetyl nitrate $(PAN)$.
Among the given options,$O_3$ is a major component of photochemical smog.

(D) The addition of phosphate-containing fertilisers to water bodies leads to a process known as $Eutrophication$.
Phosphates act as limiting nutrients for aquatic plants.
When these fertilisers enter water bodies,they promote the excessive growth of algae,which is known as an algal bloom.
This excessive growth eventually leads to the depletion of dissolved oxygen in the water,which can harm aquatic life.

(B) Freons and chlorofluorocarbons reach the stratosphere without being destroyed in the troposphere due to their low reactivity.
In the stratosphere,the $Cl$ and $Br$ atoms are liberated from the parent compound by the action of ultraviolet light.
For example:
$CF_2Cl_2 + h\nu \to CF_2Cl^{\bullet} + Cl^{\bullet}$
$CFCl_3 + h\nu \to CFCl_2^{\bullet} + Cl^{\bullet}$
The $Cl^{\bullet}$ atoms destroy ozone molecules through catalytic cycles.
The problem is more serious at the poles because ice crystals in polar stratospheric clouds provide a surface for these reactions to occur more efficiently.

(B) Global warming is primarily caused by the increase in greenhouse gases in the atmosphere. The most significant contributor is $CO_2$ (carbon dioxide),followed by methane $(CH_4)$. These gases trap heat in the Earth's atmosphere,leading to a rise in global temperatures.

(B) The Global Warming Potential $(GWP)$ is a measure of how much heat a greenhouse gas traps in the atmosphere relative to carbon dioxide $(CO_2)$.
Comparing the $GWP$ values (over a $100$-year horizon):
$CFCs$ (Chlorofluorocarbons) have a very high $GWP$ (ranging from thousands to tens of thousands).
$N_2O$ (Nitrous oxide) has a $GWP$ of approximately $273$.
$CH_4$ (Methane) has a $GWP$ of approximately $28$.
$CO_2$ (Carbon dioxide) is the reference gas with a $GWP$ of $1$.
Therefore,the correct sequence is $CFC > N_2O > CH_4 > CO_2$.

(A) The $BOD$ (Biological Oxygen Demand) value is a measure of the amount of dissolved oxygen required by bacteria to decompose organic matter in a water sample.
Clean water has a $BOD$ value of less than $5 \ ppm$,whereas highly polluted water has a $BOD$ value of more than $17 \ ppm$.

(B) $NO$ (nitric oxide) and freons (chlorofluorocarbons) are responsible for the depletion of the ozone layer in the stratosphere.

(B) According to the $WHO$ and $BIS$ standards for drinking water,the permissible limits for these metals are as follows:
$Fe$: $0.2 \ ppm$
$Mn$: $0.05 \ ppm$
$Cu$: $3.0 \ ppm$
$Zn$: $5.0 \ ppm$
In the given sample,the concentration of $Mn$ is $0.05 \ ppm$. While this is at the threshold,$Mn$ is highly sensitive; even slight variations above this limit cause staining and taste issues,making it the most critical metal among the choices that renders water unsuitable for drinking if concentrations exceed the limit.

(C) Methemoglobinemia,also known as 'blue baby syndrome',is caused by the presence of excess nitrate ions in drinking water.
When the concentration of nitrate in drinking water exceeds $50 \ ppm$,it reacts with hemoglobin in the blood to form methemoglobin,which is unable to transport oxygen effectively.
Therefore,the correct condition is $> 50 \ ppm$ of nitrate.

(A) Biological Oxygen Demand $(BOD)$ is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water.
Higher $BOD$ values indicate a higher concentration of organic pollutants in the water.
Since the $BOD$ value of glass $B$ $(20)$ is higher than that of glass $A$ $(10)$,glass $B$ is more polluted than glass $A$.

(C) The depletion of the ozone layer in the stratosphere is primarily caused by chlorofluorocarbons $(CFCs)$.
$CF_2Cl_2$ undergoes photolysis to release chlorine radicals,which then react with ozone.
$HOCl$ also acts as a reservoir species that releases reactive radicals upon photolysis.
Option $C$ represents a reaction that is not part of the standard ozone depletion mechanism in the stratosphere,as $CH_4$ reacts with chlorine radicals to terminate the chain reaction rather than depleting ozone directly in the manner described.

(C) The solubility of gases in liquids decreases with an increase in temperature.
Therefore,cold water can hold a higher concentration of dissolved oxygen compared to warm water.
The concentration of dissolved oxygen $(DO)$ in cold water can reach up to $10 \ ppm$.

(D) Photochemical smog is formed by the action of sunlight on nitrogen oxides and hydrocarbons. It produces secondary pollutants such as formaldehyde,acrolein,and peroxyacetyl nitrate $(PAN)$,which are powerful eye irritants.