Environmental Chemistry(11th And 12th > Chemistry ) Questions and answers for exam Preparation

11th And 12th > Chemistry

ENVIRONMENTAL CHEMISTRY MCQs

Total Questions : 40 | Page 1 of 4 pages

Question 1.

Gas released during Bhopal tragedy was:

Sodium isocyanate
ethyl isocyanate
Potassium isocyanate
methyl isocyanate

Discuss Question

Answer: Option D. -> methyl isocyanate
:
D

Methyl isocyanate was the principle toxic gas responsible for Bhopal tragedy.

Question 2.

A brick kiln should not be allowed near an orchard:

To save plants from soil erosion
To save fruits from laborers
To save plants from smoke and toxic gases emitted by kiln
To save plants from transport vehicles

Discuss Question

Answer: Option C. -> To save plants from smoke and toxic gases emitted by kiln
:
C

$S O_{2}$ gas produced from brick kiln causes death of plants.

Question 3.

Which of the followings pair is not present in acid rain (if any one acid in the given pair is not present, then that pair is considered to be not present)-

$H_{2} C O_{3} a n d H_{2} S O_{3}$
$H N O_{3} a n d H_{2} C O_{3}$
$H_{2} S O_{4} a n d H_{3} P O_{4}$
$H_{2} S O_{3} a n d H_{3} S O_{4}$

Discuss Question

Answer: Option C. ->

H_{2} S O_{4} a n d H_{3} P O_{4}

:
C

Acid rain is caused due to reaction of water with gaseous oxides present in atmosphere. As oxides of C, N and S are present in the form of $C O_{2}, N O_{x}, S O_{2} a n d S O_{3}$ ; their corresponding acids are present in acid rain. But $H_{3} P O_{4}$ is absent.

Question 4.

Which of the followings is incorrect?

The lowest region of atmosphere is known as Troposphere.
CO gas forms highly stable complex with blood known as carboxyhaemoglobin.
Water vapor present in the atmosphere acts as greenhouse gas.
Rain having pH value less than 7 is known as acid rain.

Discuss Question

Answer: Option D. -> Rain having pH value less than 7 is known as acid rain.
:
D

a) The lowest region of atmosphere is known as troposphere and above this region lies the stratosphere.

b) CO gas combines with hemoglobin present in blood to form carboxyhaemoglobin which is about 300 times more stable than oxyhaemoglobin. It reduces the oxygen carrying capacity of blood.

c) Atmospheric gases which are transparent to sunlight but not to heat radiation from earth surface are known as greenhouse gas. Water vapor acts as greenhouse gas. Hence

d) Rain having pH value less than 5.6 is termed as acid rain.

Question 5.

Which of the followings is incorrect about photochemical smog –

It is produced in warm, dry and sunny climate
It is oxidizing in nature.
Ozone gas is one of its constituents.
It is formed in stratosphere.

Discuss Question

Answer: Option D. -> It is formed in stratosphere.
:
D

Photochemical smog is formed in troposphere not in stratosphere. It is produced in warm, dry and sunny climate. It's main constituents are $O_{3}, N O_{2}$ and unsaturated carbons. Ozone is formed due to reaction between $N O_{2}$ and atmospheric oxygen.
$N O_{2} (g) u v - \to N O (g) + O (g)$
$O (g) + O_{2} (g) \to O_{3} (g)$

Question 6.

Assertion (A): Classical smog occurs in cold humid climate and it is acidic as well as reducing in nature.
Reason (R): It is a mixture of smoke, fog and sulphur dioxide.

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

Discuss Question

Answer: Option A. -> Both A and R are correct and R is the correct explanation of A.
:
A

Classical smog occurs in cold humid climate. It is a mixture of smoke, fog and sulphur dioxide. Presence of $S O_{2}$ makes it both acidic as well as reducing.

Question 7.

Which of the following pairs is secondary precursors of photochemical smog –

$S O_{2} a n d N O_{2}$
$S O_{2}$ and hydrocarbons
$N O_{2}$ and hydrocarbons
$O_{3}$ and PAN

Discuss Question

Answer: Option D. ->

O_{3}

and PAN
:
D

Photochemical smog does not contain $S O_{2}$ . Hence we straight away discard options (a) and (b).

$N O_{2}$ and hydrocarbons are primary precursors while $O_{3}$ , PAN, Formaldehyde, and Acrolein are secondary precursor of photochemical smog.

Question 8.

Ozone hole refers to –

Increased concentration of ozone
Reduction in the thickness of ozone layer in troposphere
Reduction in the thickness of ozone layer in stratosphere
Hole in ozone layer

Discuss Question

Answer: Option C. -> Reduction in the thickness of ozone layer in stratosphere
:
C

It refers to reduction in the thickness of ozone layer. As ozone layer exists in stratosphere, option (c) is the correct answer.

Question 9.

$C F C l_{3}$ is responsible for the decomposition of ozone layer. Which of the following reacts with ozone to form oxygen?

$C l_{2}$
$C l^{-}$
$F^{-}$
$C l^{*}$

Discuss Question

Answer: Option D. ->

C l^{*}

:
D
The free radical produced causes destruction of ozone.

C F C l_{3} (g) \to C F C l_{2}^{*} + C l^{*}

C l^{*} (g) + O_{3} (g) \to C l O^{*} + O_{2} (g)

Question 10.

Which one is not correct? Greenhouse effect:

Is mainly due to high concentration of $C O_{2}$ in atmosphere
Is influenced by gases such as $C H_{4}$ , $O_{3}$ and chlorofluorocarbons
Would result in the warming up of the earth
Would result in lowering the level of oceans due to high evaporation

Discuss Question

Answer: Option D. -> Would result in lowering the level of oceans due to high evaporation
:
D

Greenhouse effect would cause melting of polar ice caps and glaciers that will result in increasing the ocean levels, thereby causing submergence of low lying areas.