Environmental Chemistry

JEE Chemistry · 92 questions · Page 5 of 10 · Click an option or "Show Solution" to reveal answer

Q41

The concentration of fluoride, lead, nitrate and iron in a water sample from an underground lake was found to be 1000 ppb, 40 ppb, 100 ppm and 0.2 ppm, respectively. This water is unsuitable for drinking due to high concentration of :

A Lead

B Nitrate

C Iron

D Fluoride

Correct Answer

Option B

Solution

The maximum limit of nitrate in drinking water is

50

ppm. Excess nitrate in drinking water can cause disease such as methemoglobinemia ('blue baby' syndrome).

Q42

Which one of the following statements is NOT correct?

A Eutrophication indicates that water body is polluted

B The dissolved oxygen concentration below 6 ppm inhibits fish growth

C Eutrophication leads to increase in the oxygen level in water

D Eutrophication leads to anaerobic conditions

Correct Answer

Option C

Solution

Eutrophication leads to decrease in oxygen level of water. 3rd statement is incorrect.

Q43

Given below are two statements: Statement I : In polluted water values of both dissolved oxygen and

\mathrm{BOD}

are very low. Statement II : Eutrophication results in decrease in the amount of dissolved oxygen. In the light of the above statements, choose the most appropriate answer from the options given below :

A Both Statement I and Statement II are true

B Both Statement I and Statement II are false

C Statement I is true but Statement II is false

D Statement I is false but Statement II is true

Correct Answer

Option D

Solution

Since eutrophication is result of excessive growth of weed in water bodies, which consume dissolved oxygen of water bodies.

$\therefore$ Eutrophication decreases amount of dissolved oxygen in water bodies.

Polluted water has low value of dissolved oxygen, but high valueof BOD (Biological oxygen demand), since chemical and organic matter requires dissolved oxygen to get decompose.

Q44

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Photochemical smog causes cracking of rubber. Reason (R) : Presence of ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyl nitrate in photochemical smog makes it oxidizing. Choose the most appropriate answer from the options given below :

A Both (A) and (R) are true but (R) is not the true explanation of (A)

B (A) is false but (R) is true.

C (A) is true but (R) is false.

D Both (A) and (R) are true and (R) is the true explanation of (A)

Correct Answer

Option D

Solution

Photochemical smog causes cracking of rubber, the common component of photochemical smog are ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyel nitrate (PAN).

Q45

Which of the following is a set of greenhouse gases?

A CH4, O3, N2, SO2

B O3, N2, CO2, NO2

C O3, NO2, SO2, Cl2

D CO2, CH4, N2O, O3

Correct Answer

Option D

Solution

The gases that contribute to greenhouse effect are called greenhouse gases. These include CO2 , CH4 , N2O and O3.

Q46

Which of the following compounds is an example of Freon?

\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{F}_{2}

\mathrm{C}_{2} \mathrm{HF}_{3}

\mathrm{C}_{2} \mathrm{F}_{4}

\mathrm{C}_{2} \mathrm{Cl}_{2} \mathrm{F}_{2}

Correct Answer

Option D

Solution

Freons are a class of compounds which are also known as chlorofluorocarbons (CFCs).

As the name suggests, these compounds contain carbon, chlorine, and fluorine atoms.

So the compound that is an example of a Freon from the options given is : Option D :

\mathrm{C}_{2} \mathrm{Cl}_{2} \mathrm{F}_{2}

This compound contains both chlorine and fluorine atoms bonded to carbon, and is therefore a CFC or a Freon.

Q47

How can photochemical smog be controlled?

A By using catalytic convertors in the automobiles/industry.

B By complete combustion of fuel.

C By using tall chimneys.

D By using catalyst.

Correct Answer

Option A

Solution

Option A, By using catalytic converters in the automobiles/industry, is the most appropriate answer to control photochemical smog.Photochemical smog is a type of air pollution that forms in urban areas when pollutants from automobile and industrial emissions, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs), react in the presence of sunlight.Catalytic converters are devices that are installed in the exhaust systems of automobiles and in some industrial processes to remove pollutants from exhaust gases.

They work by using a catalyst to convert harmful pollutants, such as NOx and VOCs, into less harmful substances before they are released into the atmosphere.

This can significantly reduce the formation of photochemical smog.Option B, By complete combustion of fuel, is not a complete or sufficient solution to control photochemical smog.

Complete combustion of fuel, which refers to the complete oxidation of the fuel to produce carbon dioxide and water, can reduce the amount of unburned hydrocarbons and carbon monoxide in the exhaust gases.However, even with complete combustion, other pollutants, such as nitrogen oxides (NOx), can still be produced and contribute to the formation of photochemical smog.

NOx emissions are a result of high temperatures and pressures in the combustion process and are not easily prevented through complete combustion alone.Additionally, while complete combustion can reduce the amount of certain pollutants, it does not address other sources of pollution, such as industrial emissions, that can contribute to the formation of photochemical smog.Therefore, while complete combustion can be an important step in reducing emissions and controlling photochemical smog, it is not a sufficient solution on its own and must be combined with other methods, such as the use of catalytic converters, to effectively address this issue.Option C, using tall chimneys, is not a direct way to control photochemical smog.

Tall chimneys can help to disperse pollutants into the atmosphere, but do not necessarily prevent their formation in the first place.Option D, By using a catalyst, is not a complete or sufficient solution to control photochemical smog.

While catalysts can be used to convert harmful pollutants into less harmful substances, they need to be part of a larger system, such as a catalytic converter, to effectively reduce emissions.Using a catalyst alone, without the proper design, engineering, and installation, is unlikely to be effective in controlling photochemical smog.

It is important to note that the goal is to reduce the overall emissions of pollutants, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs), which are the precursors to photochemical smog.Therefore, while catalysts can be a useful tool in controlling photochemical smog, they must be used in combination with other methods, such as the use of catalytic converters in automobiles and industry, to be most effective.

Q48

Correct statement about smog is :

A NO

_2

is present in classical smog

B Both NO

_2

and SO

_2

are present in classical smog

C Photochemical smog has high concentration of oxidizing agents

D Classical smog also has high concentration of oxidizing agents

Correct Answer

Option C

Solution

Photochemical smog has high concentration of oxidising agents NO2 is produced from NO and O3 in the presence of sunlight Classical smog contain smoke, fog and SO2 and it is known as reducing smog, as chemically it is reducing mixture

Q49

Assertion : Ozone is destroyed by CFCs in the upper stratosphere. Reason : Ozone holes increase the amount of UV radiation the earth.

A Assertion and reason are both correct, and the reason is the correct explanation for the assertion.

B Assertion and reason are incorrect.

C Assertion and reason are correct but, the reason is not the explanation for the assertion

D Assertion is false, but the reason is correct.

Correct Answer

Option C

Solution

CFC’s are responsible for depletion of ozone layer.

When the ozone holes increases more UV rays will enter the earth.

So here both Assertion and reason are correct but reason is not the correct explanation for why CFC is destroying the ozone layer.

Q50

Given below are two statements : Statement I : Non-biodegradable wastes are generated by the thermal power plants. Statement II : Bio-degradable detergents leads to eutrophication. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement I is false but statement II is true.

B Both statement I and statement II are true.

C Both statement I and statement II are false.

D Statement I is true but statement is false.

Correct Answer

Option B

Solution

Non-biodegradable wastes are generated by thermal power which produce fly ash.

Nowadays most of the detergents available are biodegradable.

The bacteria responsible for degrading biodegradable detergent feed on it and grow rapidly.

While growing, they may use up all the oxygen dissolved in water which cause Eutrophication.

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