Assertion (A) & Reason (B) MCQ

MCQ 11 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below :
Assertion $(A)$ : The $\text{pH}$ of acid rain is less than $5.6.$
Reason $(R)$ : Carbon dioxide present in the atmosphere dissolves in rain water and forms carbonic acid.

A
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 $A$.
C
Both $A$ and $R$ are not correct.
D
$A$ is not correct but $R$ is correct.

Answer

Correct option: B.

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

In acid rain, $\text{pH}$ is less than $5.6$. Carbon dioxide dissolves in water to form weak acid.
$\mathrm{H}_2+\mathrm{CO}_2 \rightarrow \mathrm{H}_2 \mathrm{CO}_3$

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MCQ 21 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below:
Assertion $(A)$ : Carbon dioxide is one of the important greenhouse gases.
Reason $(R)$ : It is largely produced by respiratory function of animals and plants.

A
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 $A.$
C
Both $A$ and $R$ are not correct.
D
$A$ is not correct but $R$ is correct.

Answer

Correct option: B.

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

The increased amount of $\text{CO}_2$ in the air mainly responsible for global warming. A large amount of carbon dioxide gets released into the atmosphere.
Excess of $\text{CO}_2$ in the air is romoved by green plants and this maintains an appropriate level of $\text{CO}_2$ in the atmosphere.

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MCQ 31 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below:
Assertion $(A)$ : Green house effect was observed in houses used to grow plants and these are made of green glass.
Reason $(R)$ : Green house name has been given because glass houses are made of green glass.

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 $A.$
✓
Both $A$ and $R$ are not correct.
D
$A$ is not correct but $R$ is correct.

Answer

Correct option: C.

Both $A$ and $R$ are not correct.

$A$ and $R$ both are not correct. In cold places, sunlight required to grow plants which is less.
Hence, plants are kept in a glass house so that sunlight enters in the green house to heat up the soil and plants. The warm soil and plants emit infrared radiations which are partially absorbed and partially reflected by the glass.

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MCQ 41 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below:
Assertion $(A)$ : If $\text{BOD}$ level of water in a reservoir is less than $5$ ppm it is highly polluted.
Reason $(R)$ : High biological oxygen demand means low activity of bacteria in water.

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 $A$.
✓
Both $A$ and $R$ are not correct.
D
$A$ is not correct but $R$ is correct.

Answer

Correct option: C.

Both $A$ and $R$ are not correct.

The amount of oxygen required by bacterial to breakdown the organic matter present in a certain volume of a sample of water, is called Biochemical Oxygen Demand $\text{(BOD)}$. If $\text{BOD}$ of water is less than $5\ \text{ppm},$ it is clean. If $\text{BOD}$ increases, water pollution increases.

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MCQ 51 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below:
Assertion $(A)$ : Photochemical smog is oxidising in nature.
Reason $(R)$ : Photochemical smog contains $\text{NO}_2$ and $\text{O}_3$ , which are formed during the sequence of reactions.

✓
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
Both $A$ and $R$ are not correct.
D
$A$ is not correct but $R$ is correct.

Answer

Correct option: A.

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

Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$. Photochemical smog has high concentration of oxidizaing agents and is, therefore, called as oxidizaing smog.
Two of the pollutants that are emitted are hydrocarbons $($unburnt fuels$)$ and nitric oxide $\ce{(NO)}$. When these pollutants build up to sufficiently high levels, a chain reaction occurs from their interaction with sunlight in which $\ce{NO}$ is converted into nitrogen dioxide $(\text{NO}_2).$
This $\text{NO}_2$ in turn absorbs energy from sunlight and breaks up into nitric oxide and free oxygen atom.
$\text{NO}_2\text{(g)}\xrightarrow{ \ \ \ \ \ \ \text{h}\upsilon \ \ \ \ \ }\text{NO}\text{(g)}+\text{O}\text{(g)}$
$\text{O}\text{(g)}+\text{O}_2\text{(g)}\rightarrow\text{O}_3\text{(g)}$

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Question 61 Mark

Assertion: Green house effect was observed in houses used to grow plants and these are made of green glass.
Reason: Green house name has been given because glass houses are made of green glass.

Answer

Both Assertion and Reason are false.

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MCQ 71 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below:
Assertion $(A)$ : Excessive use of chlorinated synthetic pesticides causes soil and water pollution.
Reason $(R)$ : Such pesticides are non-biodegradable.

✓
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
Both $A$ and $R$ are not correct.
D
$A$ is not correct but $R$ is correct.

Answer

Correct option: A.

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

Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$. Pesticides are basically synthetic toxic chemicals with ecological repercussions. The repeated use of the same or similar pesticides give rise to pests that are resistant to that group of pesticides thus making the pesticides ineffective.
Therefore, as insect resistance of $\text{DDT}$ increased, other organic toxins such as Aldrin and Dieldrin were intorduced in the market by pesticide industry. Most of the organic toxins are water insoluble and non-biodegradable.

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MCQ 81 Mark

Note : In the following question a statement of Assertion $(A)$ followed by a statement of Reason $(R)$ is given. Choose the correct option out of the choices given below :
Assertion $(A)$ : Ozone is destroyed by solar radiation in upper stratosphere.
Reason $(R)$ : Thinning of the ozone layer allows excessive $\text{UV}$ radiations to reach the surface of earth.

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
Both $A$ and $R$ are not correct.
✓
$A$ is not correct but $R$ is correct.

Answer

Correct option: D.

$A$ is not correct but $R$ is correct.

$A$ is not correct but $R$ is correct. Ozone in the stratosphere is a product of $\text{UV}$ radiations acting on dioxygen $(\text{O}_2)$ molecules. The main reason of Ozone layer depletion is believed to be the release of chloroflurocarbon compounds $\text{(CFCs)},$ also known as freons. With the depletion of ozone layer, more $\text{UV}$ radiations filters into troposphere. $\text{UV}$ radiations lead to ageing of skin, cataract, sunburn, skin cancer, killing of many phytoplankton's, damage to fish productivity etc.

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Chemistry Assertion (A) & Reason (B) MCQ

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