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Environmental Chemistry

NEET Chemistry · 96 questions · Page 4 of 10 · Click an option or "Show Solution" to reveal answer

Q31
Excessive release of CO2 into the atomosphere results in :
A depletion of ozone
B polar vortex
C global warming
D formation of smog
Correct Answer
Option C
Solution

CO2 causes global warming.

Q32
The green house gas/es is (are) : (A) Carbon dioxide (B) Oxygen (C) Water vapour (D) Methane Choose the most appropriate answer from the options given below :
A (A) and (C) only
B (A) and (B) only
C (A), (C) and (D) only
D (A) only
Correct Answer
Option C
Solution

Greenhouse gases are CO2, CH4, Water vapour, Nitrous oxide, CFCs and ozone.

Q33
Which of these reactions is not a part of breakdown of ozone in stratosphere?
A CF2Cl2(g)⟶uvC∙l(g)+C∙F2Cl(g)\mathrm{C{F_2}C{l_2}(g)\overset{{uv}}\longrightarrow \mathop C\limits^ \bullet l(g) + \mathop C\limits^ \bullet {F_2}Cl(g)}
B Cl∙(g)+O3(g)⟶ClO∙(g)+O2(g)\mathrm{C\mathop l\limits^ \bullet (g) + {O_3}(g)\overset{{}}\longrightarrow Cl\mathop O\limits^ \bullet (g) + {O_2}(g)}
C 2ClO∙⟶ClO2(g)+Cl∙(g)\mathrm{2Cl\mathop O\limits^ \bullet \overset{{}}\longrightarrow Cl{O_2}(g) + C\mathop l\limits^ \bullet (g)}
D ClO∙(g)+O(g)⟶Cl∙(g)+O2(g)\mathrm{Cl\mathop O\limits^ \bullet (g) + O(g)\overset{{}}\longrightarrow C\mathop l\limits^ \bullet (g) + {O_2}(g)}
Correct Answer
Option C
Solution

The breakdown of ozone in the stratosphere largely involves a series of reactions often initiated by free radicals, such as chlorine (Cl), bromine (Br), or nitric oxide (NO) radicals.

In particular, chlorine atoms, which can come from substances like chlorofluorocarbons (CFCs), can catalyze the destruction of ozone.

The first three reactions listed are all part of the ozone breakdown process: Option A: This is the photodissociation of a chlorofluorocarbon, which releases a chlorine atom (a free radical) that can participate in ozone destruction.

CF2Cl2(g)→uvCl(g)+CF2Cl(g)\mathrm{CF_2Cl_2(g) \xrightarrow{uv} Cl(g) + CF_2Cl(g)}

Option B: This reaction shows a chlorine atom catalyzing the destruction of ozone, forming ClO and O2.

Cl(g)+O3(g)→ClO(g)+O2(g)\mathrm{Cl(g) + O_3(g) \rightarrow ClO(g) + O_2(g)}

Option D: This reaction shows a ClO radical reacting with a single oxygen atom to regenerate the Cl radical and form O2.

The regenerated Cl radical can then go on to catalyze more ozone destruction, making this a catalytic cycle.

ClO(g)+O(g)→Cl(g)+O2(g)\mathrm{ClO(g) + O(g) \rightarrow Cl(g) + O_2(g)}

However, option C:

2ClO→ClO2+Cl\mathrm{2ClO \rightarrow ClO_2 + Cl}

This reaction is not typically part of the ozone breakdown process.

Chlorine monoxide (ClO) radicals generally react with atomic oxygen (O), not with another ClO radical, to regenerate the chlorine radical and produce oxygen (O2).

The product of this reaction, ClO2, does not commonly appear in the standard ozone depletion mechanisms.

Q34
Biochemical Oxygen Demand (BOD) is the amount of oxygen required (in ppm) :
A for sustaining life in a water body.
B by anaerobic bacteria to breakdown inorganic waste present in a water body.
C for the photochemical breakdown of waste present in 1 m3 volume of a water body.
D by bacteria to break-down organic waste in a certain volume of a water sample.
Correct Answer
Option D
Solution

Biochemical oxygen demand (BOD) is amount of oxygen required by bacteria to break down organic waste in a certain volume of water sample.

Q35
Which of the following is true about freons?
A These are radicals of chlorine and chlorine monoxide
B These are chemicals causing skin cancer
C All radicals are called freons
D These are chlorofluorocarbon compounds
Correct Answer
Option D
Solution

Freons are a family of chlorofluorocarbon (CFC) compounds, which are chemicals that contain chlorine, fluorine, and carbon atoms.

They are used in a variety of applications, including refrigeration and air conditioning, as well as in aerosol spray cans.

Q36
The correct set of species responsible for the photochemical smog is :
A NO, NO2, O3 and hydrocarbons
B N2, NO2 and hydrocarbons
C CO2, NO2, SO2 and hydrocarbons
D N2, O2, O3 and hydrocarbons
Correct Answer
Option A
Solution

Photochemical smog contains oxides of nitrogen, ozone and hydrocarbons.

Q37
The conversion of hydroxyapatite occurs due to presence of F−- ions in water. The correct formula of hydroxyapatite is :
A [3Ca3(PO4)2 . Ca(OH)2]
B [3Ca(OH)2 . CaF2]
C [Ca3(PO4)2 . CaF2]
D [3Ca3(PO4)2 . CaF2]
Correct Answer
Option A
Solution

The F

Θ\Theta

ions make the enamel on teeth much harder by converting hydroxyapatite, [3Ca3(PO4)2] .

Ca(OH)2], the enamel on the surface of the teeth into much harder fluroappatite.

[3Ca3(PO4)2 .

CaF2]

Q38
The radical which mainly causes ozone depletion in the presence of UV radiations is :
A NO⋅\mathrm{NO}^\cdot
B CH3⋅\mathrm{CH}_{3} ^\cdot
C Cl˙\dot{\mathrm{Cl}}
D O˙H\dot{\mathrm{O}} \mathrm{H}
Correct Answer
Option C
Solution

The radical that mainly causes ozone depletion in the presence of UV radiation is Cl˙\dot{\mathrm{Cl}}.

The chloro radical reacts with ozone molecules to form chlorine monoxide and oxygen:

Cl˙+O3→ClO+O2\dot{\mathrm{Cl}} + \mathrm{O}_{3} \rightarrow \mathrm{ClO} + \mathrm{O}_{2}

This reaction depletes the ozone layer, as the chlorine monoxide can then go on to react with another ozone molecule:

ClO+O3→Cl+2O2\mathrm{ClO} + \mathrm{O}_{3} \rightarrow \mathrm{Cl} + \mathrm{2O}_{2}

Thus, Cl˙\dot{\mathrm{Cl}}, is the correct answer.

Q39
The possibility of photochemical smog formation will be minimum at :
A Mumbai in May
B Kolkata in October
C New-Delhi in August (Summer)
D Srinagar, Jammu and Kashmir in January
Correct Answer
Option D
Solution

The formation of photochemical smog depends on several factors, including sunlight, temperature, and the presence of pollutants such as nitrogen oxides and volatile organic compounds.

Option (A) Mumbai in May may also have some possibility of photochemical smog formation because the temperature and sunlight are relatively high in May.

Option (B) Kolkata in October may have some possibility of photochemical smog formation because the temperature and sunlight are still relatively high in October.

Option (C) New-Delhi in August (Summer) is more likely to have photochemical smog formation because the temperature and sunlight are at their peak in the summer months, and there is a high level of air pollution in the city due to various anthropogenic activities.

Option (D) Srinagar, Jammu and Kashmir in January is less likely to have photochemical smog formation because the winter season typically has less sunlight and lower temperatures, which are not conducive to the formation of photochemical smog.

Therefore, the answer is (D) Srinagar, Jammu and Kashmir in January, as it is the option with the least possibility of photochemical smog formation.

Q40
Water samples with BOD values of 4 ppm and 18 ppm, respectively are :
A Clean and Highly polluted
B Highly polluted and Clean
C Highly polluted and Highly polluted
D Clean and Clean
Correct Answer
Option A
Solution

Clean water would have BOD value of less than 5 ppm whereas highly polluted water could have a BOD value of 17 ppm or more.

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