Environmental Chemistry MCQ Quiz in मल्याळम - Objective Question with Answer for Environmental Chemistry - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is: 1) 2, 1, 4, 3

Photochemical smog, also known as "Los Angeles smog," is a type of air pollution produced when sunlight reacts with nitrogen oxides (NO_x) and volatile organic compounds (VOCs) in the atmosphere. This reaction leads to the formation of a mixture of pollutants, including ozone, aldehydes, and peroxyacyl nitrates (PAN). The sequence of reactions leading to photochemical smog involves various steps that culminate in the formation of these harmful compounds.

Key Points

Steps Involved in the Formation of Photochemical Smog:

• Generation of Oxygen Atoms by Photochemical Reaction:
  • Sunlight breaks down nitrogen dioxide (NO₂) into nitrogen oxide (NO) and a free oxygen atom (O).
  • The equation for this reaction is NO₂ + UV light → NO + O.
  • This step is crucial as it provides the free oxygen atoms that further react with oxygen molecules to form ozone (O₃).
• Formation of Hydrocarbon Peroxides:
  • Free oxygen atoms react with hydrocarbons in the atmosphere to form hydrocarbon radicals.
  • These radicals further react with oxygen to form hydrocarbon peroxides.
  • The detailed reactions include the generation of various reactive volatile organic compounds (VOCs).
• Formation of Aldehyde Peroxides:
  • Hydrocarbon peroxides transform through complex reactions, involving interactions with nitrogen oxides, to produce aldehyde peroxides.
  • These reactions contribute to the formation of secondary pollutants in photochemical smog.
  • Formation of Peroxyacyl Nitrates (PAN):
    • Aldehyde peroxides react with nitrogen oxides, particularly NO₂, to form peroxyacyl nitrates (PAN).
    • PANs are significant components of photochemical smog, known for their eye-irritating properties and potential to cause respiratory problems.

  Additional Information

  • Ozone (O₃): Formed when free oxygen atoms react with O₂, ozone is a significant component of photochemical smog, contributing to respiratory problems and environmental damage.
  • Nitrogen Oxides (NO_x): Primarily emitted from vehicle exhaust and industrial processes, these compounds are key precursors in the formation of photochemical smog.
  • Volatile Organic Compounds (VOCs): Emitted from various sources, including vehicle emissions, industrial processes, and natural sources, VOCs are essential for the formation of secondary pollutants in smog.
  • Health Effects: Photochemical smog can cause various health problems, including eye irritation, respiratory issues, and aggravation of asthma and other lung diseases.
  • Environmental Impact: Photochemical smog affects plant life, reducing agricultural yields and harming natural vegetation. It also contributes to the degradation of man-made structures.
  • Control Measures: Reducing emissions of NO_x and VOCs through regulatory measures, technological advancements, and public awareness can mitigate the formation of photochemical smog.

The correct answer is 'A reaction product acting as a catalyst for the same reaction.'

Key Points

• Definition of Autocatalysis:
  • Autocatalysis occurs when a reaction product acts as a catalyst for the reaction itself, thereby increasing the rate of reaction as the reaction progresses.
  • In autocatalytic reactions, the concentration of the product can accelerate the reaction because the product also serves as the catalyst.
• An example of an autocatalytic reaction is the decomposition of hydrogen peroxide \(( \text{H}_2\text{O}_2 ) \) where one of the products, oxygen \(( \text{O}_2 ) \), further catalyzes the decomposition process.

Additional Information

• Characteristics of Autocatalytic Reactions:
  • These reactions often show a sigmoidal (S-shaped) curve when plotting concentration versus time because the reaction rate increases as the product concentration builds up.
  • This is different from typical reactions where the rate decreases as reactants are consumed.
• Autocatalysis vs. Standard Catalysis:
  • In standard catalysis, the catalyst is not consumed by the reaction, but it might not be a product of the reaction.
  • In autocatalysis, the catalyst is also a product of the reaction, creating a feedback loop that can accelerate the reaction rate.

Important Points

• Autocatalytic reactions can be significant in both biological systems and chemical industries.
• Understanding these reactions is crucial for controlling processes such as biochemical pathways, chemical manufacturing, and even the design of self-replicating systems.
• Autocatalysis is also observed in some pathological conditions, for example, the aggregation of proteins in neurodegenerative diseases.

The correct answer is 1-b, 2-c, 3-a.

Key Points

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Additional Information

• Alkanes:
  • Alkanes are saturated hydrocarbons, which means they have the maximum number of hydrogen atoms per carbon atom, with all carbon-carbon bonds being single bonds.
  • The general formula for alkanes is CnH2n+2, indicating that each carbon atom is bonded to two hydrogen atoms plus two additional hydrogen atoms at the ends of the molecule.
  • Examples of alkanes include methane (CH4), ethane (C2H6), and propane (C3H8).
• Alkenes:
  • Alkenes are unsaturated hydrocarbons containing at least one carbon-carbon double bond, which reduces the number of hydrogen atoms bonded to the carbon atoms.
  • The general formula for alkenes is CnH2n, reflecting the two fewer hydrogen atoms compared to alkanes with the same number of carbon atoms.
  • Examples of alkenes include ethene (ethylene, C2H4) and propene (propylene, C3H6).
• Alkynes:
  • Alkynes are also unsaturated hydrocarbons but with at least one carbon-carbon triple bond, further reducing the number of hydrogen atoms attached.
  • The general formula for alkynes is CnH2n-2, indicating four fewer hydrogen atoms than the corresponding alkane.
  • Examples of alkynes include ethyne (acetylene, C2H2) and propyne (C3H4).

The correct answer is Both statements are true.

Key Points

Statement 1: The decay constant (λ) is the proportionality between the size of a population of radioactive atoms and the rate at which the population decreases is true because,-

• The decay constant (λ) represents the probability per unit time that a given radioactive atom will decay.
• This constant is a measure of the stability of the radioactive isotope: a larger decay constant indicates a less stable isotope that decays more quickly.
• Mathematically, the rate of decay of a population of radioactive atoms (N) is given by the equation: \(\frac{dN}{dt} = -\lambda N \) which shows that the rate of decay is directly proportional to the size of the population, with λ as the proportionality constant.

Statement 2: The half-life (T1/2) is inversely proportional to the decay constant is true because,-

• The half-life (T1/2) of a radioactive substance is the time required for half of the radioactive atoms in a sample to decay.
• The relationship between the half-life and the decay constant is given by the formula: \(T_{1/2} = \frac{\ln(2)}{\lambda} \) where \(ln(2)\) is the natural logarithm of 2, approximately equal to 0.693.
• This equation shows that the half-life is inversely proportional to the decay constant: as the decay constant increases, the half-life decreases, and vice versa.

Additional Information

• The decay constant (λ) is fundamental to understanding radioactive decay processes. It is specific to each radioactive isotope.
• Radioactive decay follows an exponential decay law, where the number of undecayed atoms decreases exponentially over time.
• The half-life provides a convenient measure of the rate of decay that is independent of the initial quantity of the substance.
• Knowledge of both the decay constant and the half-life is essential for applications in nuclear medicine, radiocarbon dating, and nuclear power generation.

The correct answer is Hydroelectric energy
Key Points Sustainable Development Goals (SDGs):

• To bring sustainable development in the mainstream United Nations (UN) launched the 2030 Agenda for Sustainable Development and SDGs.
• It aim to plan and promote the efficient development of hydroelectric power in all aspects.
• This universal, integrated and transformative agenda aims to spur actions that will end poverty and build a more sustainable world over the next 15 years.
• There are 17 goals and 169 targets specific targets to be achieved by 2030.
• Reaching the goals requires action on all fronts – governments, businesses, civil society and people everywhere all have a role to play.
• SDGs are not legally binding.

The correct answer is A, B, C and D.

Key Points

• The biochemical oxygen demand (BOD) is a crucial environmental index for determining the relative oxygen requirements of wastewater, effluents, and polluted water.
• It refers to the quantity of oxygen required by bacteria and other microorganisms in the biochemical degradation and transformation of organic matter under aerobic conditions.
• The BOD is also interpreted as a measure of the concentration of organic material that can serve as a substrate to support the growth of microorganisms.
• The BOD test, as used for assessing the efficiency of wastewater treatment, is intended to measure some fraction of the carbonaceous oxygen demand, i.e., the oxygen consumed by heterotrophic microorganisms that utilize the organic matter of the waste in their metabolism, and not the oxygen demand exerted by autotrophic nitrifying bacteria.
• The BOD test measures the strength of the wastewater by measuring the amount of oxygen used by the bacteria as they stabilize the organic matter under controlled conditions of time and temperature.
• Biochemical oxygen demand is an important water quality parameter because it provides an index to assess the effect discharged wastewater will have on the receiving environment. 

Therefore, the correct answer is A, B, C and D. 

The correct answer is Statement I is true but Statement II is false. 

Key Points

• Ecotypes are discrete entities with clear differences which separate one ecotype from another.
• The differences are not due to the plastic response to changes in the environment but are the natural selection of locally adapted populations.
• The term ecotype was proposed by Turesson (1922) to the groupings of populations or ecological races or sub-species of a species about different environmental or habitat conditions.
• These are inter-fertile forms or biotypes of a species which possess different genetic compositions or genotypes and arise due to mutations, hybridization and isolation. 

Thus the statement I is true.

• Ecotype is the product of the genetic response of a population to a habitat.
• In ecotypes adaptations are irreversible, i.e., they retain their features even when planted in a neutral habitat.

Thus statement II is false.

Therefore, the correct answer is that statement I is true but statement II is false. 

Concept:

Poison:

• Chemicals that are toxic to life are considered to be poisons.

Explanation:

Ethylene di-chloride:

• 1,2-dichloroethane, also referred to as ethylene dichloride (EDC), is a type of chlorinated hydrocarbon.
• Mostly as a raw ingredient, EDC is used to create vinyl chloride monomer (VCM).
• Ethylene di-chloride smoke is poisonous, and concentrated ethylene dichloride vapour inhalation can have a different kinds of negative consequences on a person's health.
• Ethylene dichloride is categorised by the Occupational Safety and Health Administration (OSHA) as hazardous, flammable, and carcinogenic (having the potential to cause cancer.)

Thus, ethylene di-chloride is a type of poison smoke.

Additional InformationStomach poison:

• When pests consume the insecticide sprayed on the plant's leaves and other components during eating, they pick up stomach poisons.
• Insects can also take stomach toxins through their mouths and digestive tracts and then absorb them into their bodies.
• Examples include substances that include fluorides or arsenates.

Contact poison:

• Chemicals known as "contact poisons" harm the target organism by direct skin contact or absorption rather than inhalation or gastrointestinal upset.
• DDT is a contact toxin because it harms the skin.  

Biological poison:

• A diverse range of substances known as biological poisons is created by living things.
• These are chemicals created by living things that are harmful to other beings.

The correct answer is Both (A) and (R) are true and (R) is the correct explanation of (A).

 Key Points

• Trivalent chromium (Cr (III)) and hexavalent chromium (Cr (VI)) are the most common and stable states of Cr in soils.
• In terms of mobility, Cr (III) is almost immobile in soils.
• There are four forms of insoluble Cr (III) and All of them are difficult to dissolve; thus, Cr (III) does not easily migrate.
• This makes Chromium (III) more abundant than Chromium (VI) in the soil.

Thus the assertion is true.

• Conversely, Cr (VI) is usually present as soluble CrO4 2−, HCrO4 −, and Cr2O7 2−, which are highly mobile.
• Cr (VI) is reduced to Cr (III) by reaction with humic substances over a wide range of pH values found in the environment.
• This reaction is rapid in acid and neutral conditions, and therefore, natural soil organic matter will reduce Cr(VI) transport through groundwater when it is present.

Thus the reason is also true and it correctly explains the assertion.

Therefore, the correct answer is Both (A) and (R) are true and (R) is the correct explanation of (A).

The correct answer is (c) only.

Key PointsConsider the first statement: Chromium (III) chemical species is more toxic than Chromium (VI).

• Chromium occurs in the environment primarily in two valence states, trivalent chromium (Cr III) and hexavalent chromium (Cr VI). 
• Exposure may occur from natural or industrial sources of chromium. 
• Chromium III is much less toxic than chromium (VI). 
• The respiratory tract is also the major target organ for chromium (III) toxicity, similar to chromium (VI).
• Chromium (III) is an essential element in humans. 
• The body can detoxify some amount of chromium (VI) to chromium (III).

Thus, the first statement is incorrect. 

Consider the second statement: Dimethylmercury chemical species is more toxic than methylmercury ion.

• Dimethylmercury is readily absorbed through the skin. A severely toxic dose requires the absorption of less than 0.1mL.
• Dimethylmercury ((CH₃)₂Hg) is a flammable, colourless liquid, and one of the strongest known neurotoxins.
• Methylmercury (CH₃Hg) is the most toxic form.
• Methylmercury is the most toxic among the mercury species because of its volatility and its ability to pass through biological membranes such as the BBB and the placental barrier.
• The nervous system and kidneys are the two major target organs.

Thus, the second statement is incorrect.

Consider the third statement: Arsenic (III) is more toxic than Arsenic (V).

• Arsenic occurs in two oxidation states a trivalent form, arsenite (As2O3; As III) and a pentavalent form, arsenate (As2O5; As V).
• As (III) is 60 times more toxic than As (V).
• Organic arsenic is non-toxic whereas inorganic arsenic is toxic.

​Thus, the third statement is correct.

Therefore, the correct answer is (c) only.