Environmental Chemistry

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

Q91

Given below are two statements: Statement I : If BOD is 4 ppm and dissolved oxygen is 8 ppm, then it is a good quality water. Statement II : If the concentration of zinc and nitrate salts are

5 ~\mathrm{ppm}

each, then it can be a good quality water. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement I is incorrect but Statement II is correct

B Both the statements I and II are incorrect

C Both the statements I and II are correct

D Statement I is correct but Statement II is incorrect

Correct Answer

Option C

Solution

Statement I : If BOD is 4 ppm and dissolved oxygen is 8 ppm, then it is a good quality water.

Statement II : If the concentration of zinc and nitrate salts are 5 ppm each, then it can be a good quality water.

The Biochemical Oxygen Demand (BOD) measures the quantity of oxygen used by microorganisms in the oxidation of organic matter.

Lower values of BOD indicate better water quality.

A BOD value of less than 5 ppm indicates good quality water.

Therefore, in Statement I, the BOD value of 4 ppm indicates good water quality.

Dissolved oxygen (DO) refers to the level of free, non-compound oxygen present in water.

DO levels above 5-6 ppm are generally good for aquatic life.

In Statement I, the DO level of 8 ppm suggests the water is of good quality.

The concentration of zinc in clean water should not exceed 5 ppm and the concentration of nitrates should not exceed 50 ppm.

In Statement II, both zinc and nitrate concentrations are given as 5 ppm, which are within their respective permissible limits, therefore suggesting the water can be of good quality.

Hence, based on this analysis : Option C : Both the statements I and II are correct.

Q92

The industrial activity held least responsible for global warming is :

A manufacturing of cement

B Electricity generation in thermal power plants

C steel manufacturing

D Industrial production of urea

Correct Answer

Option D

Solution

Option A (manufacturing of cement) is a significant contributor to global greenhouse gas emissions, as the production of cement releases large amounts of carbon dioxide (CO2).

Option B (electricity generation in thermal power plants) is also a major contributor, as burning fossil fuels such as coal, natural gas, and oil to generate electricity releases large amounts of CO2 and other greenhouse gases into the atmosphere.

Option C (steel manufacturing) also has a significant impact, as the production of steel requires high temperatures and the use of large amounts of energy, which can come from the burning of fossil fuels.

Option D (Industrial production of urea) has a lower impact compared to the other options, as it is a less energy-intensive process and does not directly release greenhouse gases into the atmosphere.

However, the production of urea does rely on the use of natural gas as a feedstock, which does result in the release of some greenhouse gases.

Q93

Given below are two statements : Statement I : An allotrope of oxygen is an important intermediate in the formation of reducing smog. Statement II : Gases such as oxides of nitrogen and sulphur present in troposphere contribute to the formation of photochemical smog. In the light of the above statements, choose the correct answer from the options given below :

A Statement I is false but Statement II is true

B Both Statement I and Statement II are false

C Both Statement I and Statement II are true

D Statement I is true but Statement II is false

Correct Answer

Option B

Solution

Reducing smog as is acts as reducing agent, the reducing character is due to presence of sulphur dioxide and carbon particles.

Q94

Taj Mahal is being slowly disfigured and discoloured. This is primarily due to :

A acid rain

B soil pollution

C global warming

D water pollution

Correct Answer

Option A

Solution

Taj mahal is slowely disfigured and discoloured due to acid rain.

The primary acid component of acid rain is sulfuric acid(H2SO4) which reacts with Marble(CaCO3) and gives aqueous ion.

This aqueous ions get washed away in the water flow and marble get disfigured and discoloured.

CaCO3(s) + H2SO4 $\to$ Ca2+(aq) + SO42-(aq) + H2O + CO2

Q95

Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R. Assertion A : Polluted water may have a value of BOD of the order of 17 ppm. Reason R : BOD is a measure of oxygen required to oxidise both the bio-degradable an non-biodegradable organic material in water. In the light of the above statements, choose the most appropriate answer from the options given below.

A Both A and R are correct and R is the correct explanation of A.

B Both A and R are correct but R is NOT the correct explanation of A.

C A is correct but R is not correct.

D A is not correct but R is correct.

Correct Answer

Option C

Solution

Highly polluted water could have a BOD value of 17 ppm or more.

The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen demand (BOD).

Hence A is correct but R is not correct.

Q96

The measured BOD values for four different water samples (A-D) are as follows: A = 3 ppm; B = 18 ppm; C = 21 ppm; D = 4 ppm. The water samples which can be called as highly polluted with organic wastes, are :

A A and B

B A and D

C B and C

D B and D

Correct Answer

Option C

Solution

Highly polluted water should have BOD value of 17 ppm or more

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