All questions of Assertion & Reasoning for UGC NET Exam

Problem:
A vessel is full of a mixture of methanol and ethanol in which there is 20% ethanol. 10 litres of mixture are drawn off and filled with methanol. If the ethanol is now 15%, what is the capacity of the vessel?

Solution:
Let us assume that the vessel has a capacity of x liters.

Initial Mixture:
Initially, the mixture in the vessel contains 20% ethanol.
So, the amount of ethanol in the initial mixture = (20/100) * x = 0.2x liters.
And, the amount of methanol in the initial mixture = (80/100) * x = 0.8x liters.

When 10 liters of the initial mixture is drawn off, the amount of ethanol and methanol in the mixture will be:

Ethanol: (20/100) * 10 = 2 liters
Methanol: (80/100) * 10 = 8 liters

After drawing off 10 liters of the mixture, the vessel contains (x - 10) liters of the initial mixture.

Now, 10 liters of methanol is added to the mixture. So, the amount of methanol in the mixture will be:

Methanol: 8 + 10 = 18 liters

And, the amount of ethanol in the mixture will remain the same, i.e., 2 liters.

Final Mixture:
The final mixture contains 15% ethanol.
So, the amount of ethanol in the final mixture = (15/100) * x liters.
And, the amount of methanol in the final mixture = (85/100) * x liters.

We know that the amount of ethanol in the final mixture is (amount of ethanol in the initial mixture - 10 + 0) liters.

So, we can write the equation:

(15/100) * x = 0.2x - 10

Solving this equation, we get:

x = 40 liters

Therefore, the capacity of the vessel is 40 liters.

Answer: (a) 40 liters

Assertion and Reasoning

Assertion (A): Earth is the only planet known to have life.
Reasoning (R): Earth has no atmosphere which is a mixture of oxygen, nitrogen, and carbon dioxide.

Explanation:

This is an assertion and reasoning type question. Let's analyze the given statements one by one.

Assertion (A): Earth is the only planet known to have life.

The assertion is correct. To date, no other planet has been discovered that has life on it. Earth is unique in that it has the right combination of factors such as the right distance from the sun, a suitable atmosphere, and a magnetic field that protects it from solar winds, which makes it capable of sustaining life.

Reasoning (R): Earth has no atmosphere which is a mixture of oxygen, nitrogen, and carbon dioxide.

The reasoning is incorrect. Earth's atmosphere is a mixture of several gases including oxygen, nitrogen, and carbon dioxide. These gases provide the necessary conditions for life to exist on Earth. Oxygen, for instance, is essential for respiration, while nitrogen is needed for the synthesis of amino acids, the building blocks of proteins, which are essential for life.

Therefore, both the assertion and reasoning are true, but the reasoning does not explain the assertion. The correct answer is option (A).

The correct option is:

A) Assertion (A) is true, but Reason (R) is false.

Explanation:

Assertion (A) states that there is a rainbow in the sky only after rains. This statement is true because raindrops act as tiny prisms that refract and reflect sunlight, creating the optical phenomenon known as a rainbow.

Reason (R) states that water drops suspended in the air break up sun. This statement is false because water droplets do not break up the sun. Instead, they act as a medium for the dispersion and refraction of sunlight, which leads to the formation of a rainbow.

- Assertion (A): Telephone wires sag more in summer.
- Reason (R): They expand due to summer heat.



- Assertion (A) is true: Telephone wires are made of materials that expand when exposed to heat, such as during the summer. This expansion causes the wires to sag more in summer compared to other seasons.

- Reason (R) is true: The reason for the sagging of telephone wires in summer is indeed the expansion of the wires due to the heat. As the temperature rises, the wires expand, leading to sagging.



Therefore, both the Assertion (A) and the Reason (R) are true in this case. The Reason (R) correctly explains why the Assertion (A) is true. The expansion of telephone wires due to summer heat is why they sag more during this season.

Assertion (A) : Leakages in household gas cylinders can be detected.
Reason (R) : LPG has a strong smell.

The correct option for this question is option 'C', which states that Assertion (A) is true but Reason (R) is false.

Explanation:

Assertion (A) : Leakages in household gas cylinders can be detected.
This statement is true. Leakages in household gas cylinders can indeed be detected through various means. Gas cylinders are designed with safety features to detect and prevent leakages. Some common methods to detect gas leaks include:

1. Smell: LPG (liquefied petroleum gas), which is commonly used in household gas cylinders, has a strong smell added to it. This is done intentionally to help people detect gas leaks easily. If there is a gas leakage, the strong smell of LPG becomes noticeable, alerting people to the danger.

2. Sound: Gas leaks can also be detected by listening for a hissing sound. If there is a leakage, gas escapes from the cylinder, creating a distinct sound that can be heard.

3. Soap Water Test: Another method to detect gas leaks is by using the soap water test. This involves applying a soapy solution to the gas cylinder valve and checking for the formation of bubbles. If bubbles form, it indicates a gas leak.

4. Gas Detectors: Gas detectors are devices specifically designed to detect the presence of gas leaks. These detectors use sensors to detect the gas concentration in the air and trigger an alarm if it exceeds a certain threshold.

Therefore, it is clear that leakages in household gas cylinders can be detected through various means.

Reason (R) : LPG has a strong smell.
This statement is false. LPG does not have a strong smell naturally. In its pure form, LPG is odorless and colorless. However, to ensure safety, a strong odorant called ethanethiol is added to LPG. This odorant gives LPG its characteristic smell, making it easier to detect gas leaks. Without the added odorant, it would be difficult to detect gas leaks as LPG is otherwise odorless.

Hence, the reason given is incorrect as LPG does not naturally have a strong smell.

Assertion (A): DDT has nowadays lost its use as an insecticide.
Reason (R): DDT has harmful to man.


The correct answer is option 'B': Both A and R are true but R is not the correct explanation of A.


Explanation:

DDT and its Use as an Insecticide:
DDT, short for dichlorodiphenyltrichloroethane, is a synthetic pesticide that was widely used as an insecticide in the past. It was highly effective in controlling pests and played a significant role in reducing the spread of diseases like malaria and typhus.

Loss of Use:
However, over time, DDT has lost its popularity and is no longer widely used as an insecticide. There are several reasons for this decline in usage:

1. Environmental Impact: DDT is a persistent organic pollutant. It does not easily break down in the environment and can accumulate in the food chain. This poses a significant threat to wildlife, particularly birds and fish. The harmful effects of DDT on birds, including thinning of eggshells, were observed, leading to population decline.

2. Resistance Development: Prolonged and widespread use of DDT led to the development of insecticide resistance in many pest species. This means that the insects have become less susceptible to the effects of DDT, making it less effective in controlling them.

3. Health Concerns: DDT has been linked to various health issues in humans. Although it was initially considered safe and widely used for pest control, studies have shown that long-term exposure to DDT can have adverse effects on human health. It has been associated with reproductive and developmental problems, as well as certain types of cancer.

Harmful to Humans:
The Reason (R) states that DDT is harmful to humans. This statement is true. While DDT was used extensively in the past, its harmful effects on human health have become a cause for concern. Prolonged exposure to DDT has been associated with various health issues, including:

1. Reproductive and Developmental Problems: DDT has been linked to adverse effects on reproductive health, such as infertility, miscarriages, and birth defects. It can disrupt hormone function and interfere with normal reproductive processes.

2. Cancer Risk: Studies have shown a potential link between DDT exposure and certain types of cancer, including breast cancer and non-Hodgkin's lymphoma.

3. Endocrine Disruption: DDT is known to disrupt the endocrine system, which regulates hormone production and function in the body. This can lead to hormonal imbalances and associated health problems.

However, it is important to note that the Reason (R) does not provide a correct explanation for the Assertion (A). The loss of use of DDT as an insecticide is primarily due to environmental concerns, resistance development, and regulatory restrictions. While the harmful effects on human health contribute to its decline in usage, they are not the sole reason for it. Hence, option 'B' is the correct answer.

Assertion (A) : Clothes are not washed properly in hot water.
Reason (R) : Hard water contains many minerals.

The correct option is (a) Both A and R are true but R is not the correct explanation of A.

Explanation:
To understand why option (a) is the correct answer, let's analyze both the assertion and reason given in the question.

Assertion (A) : Clothes are not washed properly in hot water.
This statement implies that washing clothes in hot water does not effectively clean them.

Reason (R) : Hard water contains many minerals.
This statement suggests that the reason for clothes not being washed properly in hot water is because hard water contains minerals.

Now let's break down the explanation into the following sections:

Understanding Assertion (A): Clothes are not washed properly in hot water.
- Washing clothes involves removing dirt, stains, and other impurities from the fabric.
- Hot water is often used for washing clothes as it helps to dissolve and remove dirt and stains more effectively.
- However, Assertion (A) states that clothes are not washed properly in hot water, indicating that hot water does not result in effective cleaning of clothes.

Understanding Reason (R): Hard water contains many minerals.
- Hard water is water that contains a high concentration of minerals, such as calcium and magnesium.
- When hard water is used for washing clothes, the minerals in the water can interfere with the cleaning process.
- The minerals in hard water can react with soap or detergent, forming insoluble compounds that can leave residue on clothes.
- This residue can make clothes appear dull, faded, or not properly clean.

Evaluating the relationship between Assertion (A) and Reason (R)
- Both Assertion (A) and Reason (R) are true.
- Clothes washed in hot water may not be properly cleaned due to the presence of minerals in hard water.
- However, Reason (R) does not directly explain why clothes are not washed properly in hot water.
- While hard water can contribute to inefficient cleaning, it is not the sole reason for clothes not being washed properly in hot water.
- Other factors such as inadequate detergent, improper washing technique, or insufficient rinsing can also affect the cleanliness of clothes.

Conclusion
In conclusion, option (a) is the correct answer as both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

Assertion (A) : Akbar founded Din-e-Ilahi.
Reason (R) : He was motivated by self glorification.

The correct answer is option 'C' i.e. A is true but R is false.

Explanation:

Akbar, the Mughal emperor, did not found Din-e-Ilahi. Din-e-Ilahi was a syncretic religious movement that was initiated by Akbar, but it did not gain much popularity and did not have a lasting impact. Therefore, Assertion (A) is false.

Akbar was motivated by a desire for religious harmony and tolerance, rather than self-glorification. He was known for his policy of religious tolerance and his efforts to create a multicultural and pluralistic society. He abolished the Jizya tax on non-Muslims, promoted interfaith dialogue, and invited scholars from different religious backgrounds to his court. Therefore, Reason (R) is false.

In conclusion, neither Assertion (A) nor Reason (R) is true.

Understanding the Assertion and Reason
In evaluating the statements provided, we see that the Assertion (A) and Reason (R) both pertain to Shivaji Maharaj, a prominent historical figure in India.

Assertion (A): Shivaji developed guerilla warfare.
- This statement is **true**.
- Shivaji is credited with innovating guerilla tactics that utilized the terrain of the Western Ghats to his advantage, allowing him to effectively combat larger Mughal forces.

Reason (R): Shivaji feared the Mughals.
- This statement is **false**.
- While Shivaji was aware of the Mughal power and their military capabilities, it is inaccurate to say he "feared" them. Instead, he exhibited strategic planning and boldness in his campaigns against them.

Conclusion
- Given the analysis above, we conclude that:
- Assertion (A) is true.
- Reason (R) is false.
Thus, the correct option is **d) A is true but R is false.**
In summary, Shivaji's development of guerilla warfare was a testament to his military genius rather than a response born out of fear. He strategically engaged the Mughals, showcasing his prowess as a leader and tactician.

Assertion (A) : A ship rises as it enters the sea from a river.
Reason (R) : The density of sea water is higher as compared to river water.

The correct answer is option 'B', which states that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

Explanation:
When a ship enters the sea from a river, it appears to rise. This phenomenon can be explained by considering the density of sea water compared to river water.

Density of Water:
Density is defined as the mass per unit volume of a substance. In the case of sea water and river water, the density is determined by the presence of dissolved salts and minerals.

Density of Sea Water:
Sea water contains a higher concentration of dissolved salts and minerals compared to river water. This higher concentration increases the density of sea water. The average density of sea water is around 1025 kg/m³.

Density of River Water:
River water, on the other hand, has a lower concentration of salts and minerals, resulting in a lower density. The average density of river water is around 1000 kg/m³.

Archimedes' Principle:
To understand why a ship rises when it enters the sea from a river, we can refer to Archimedes' principle. According to this principle, an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the object.

Explanation of the Phenomenon:
When a ship enters the sea from a river, it transitions from a less dense medium (river water) to a denser medium (sea water). As sea water has a higher density, it exerts a greater upward buoyant force on the ship compared to river water.

This increase in buoyant force causes the ship to rise. The ship displaces a volume of sea water equal to its own weight, and the resulting upward force counteracts the downward force of gravity, causing the ship to float higher in the water.

Therefore, the reason provided in the statement is the correct explanation for the assertion. The ship rising when it enters the sea from a river is a result of the denser sea water exerting a greater buoyant force on the ship.

Assertion (A) : Increase in carbon dioxide would melt polar ice.
Reason (R) : Global temperature would rise.

The correct answer is option 'B': Both A and R are true and R is the correct explanation of A.

Explanation:

Assertion: Increase in carbon dioxide would melt polar ice.
Reason: Global temperature would rise.

The given assertion and reason are related to the impact of carbon dioxide on polar ice and global temperature. Let's analyze each statement individually and then see how they are interconnected.

Assertion (A): Increase in carbon dioxide would melt polar ice.

The assertion states that an increase in carbon dioxide (CO2) would lead to the melting of polar ice. This is true because carbon dioxide is a greenhouse gas that traps heat in the atmosphere. When there is a higher concentration of CO2 in the atmosphere, it enhances the greenhouse effect, leading to a rise in global temperature. As a result, the polar ice starts to melt, causing a rise in sea levels.

Reason (R): Global temperature would rise.

The reason given is that global temperature would rise. This is also true because carbon dioxide and other greenhouse gases trap heat from the sun and prevent it from escaping back into space. This trapped heat leads to an increase in global temperature, known as global warming.

Explanation of the connection between Assertion and Reason:

The reason provided is the correct explanation of the assertion. The increase in carbon dioxide levels in the atmosphere leads to a rise in global temperature, which in turn causes the melting of polar ice. The greenhouse effect caused by carbon dioxide is responsible for the warming of the Earth's surface, including the polar regions.

Therefore, both the assertion and reason are true, and the reason correctly explains why an increase in carbon dioxide would result in the melting of polar ice. Hence, the correct answer is option 'B': Both A and R are true and R is the correct explanation of A.

Explanation:

Graphite is slippery due to its unique structure and properties. The assertion (A) states that graphite is slippery and used as a lubricant, which is true.

Reasoning:

The reason (R) provided states that graphite has free electrons. This is also true as graphite has a layered structure with weak van der Waals forces between the layers. These weak forces allow the layers to slide over each other easily, making graphite slippery. The presence of free electrons in the structure also contributes to its lubricating properties.

Therefore, both assertion (A) and reason (R) are true, but the reason (R) does not provide a correct explanation for the assertion (A). The slipperiness of graphite is primarily due to its layered structure and weak intermolecular forces, rather than the presence of free electrons.

Explanation:

Assertion (A) is true but Reason (R) is false
- Assertion (A) is true: Eskimos, also known as the Inuit people, are indigenous people who traditionally reside in the Arctic regions, such as Alaska, Canada, and Greenland. In the past, Eskimos used igloos as temporary shelters during hunting trips or when traveling. However, modern-day Eskimos mostly live in permanent houses and igloos are now mainly used for cultural or ceremonial purposes.
- Reason (R) is false: While it is true that snow is a commonly used material for building igloos due to the abundance of snow in the Arctic regions, Eskimos have access to other materials as well. In modern times, Eskimos have adopted more permanent housing structures made of wood, metal, and other materials. Additionally, igloos are not the only type of housing traditionally used by Eskimos; they also build tents, sod houses, and other structures depending on the season and purpose.

Assertion (A) : Beri-beri is a viral infection.
Reason (R) : Vitamin deficiency causes diseases.

The correct answer is option 'C' - A is false but R is true.

Explanation:
Beri-beri is not a viral infection, but rather a nutritional deficiency disease caused by a lack of thiamine (vitamin B1). Therefore, Assertion (A) is false.

On the other hand, the Reason (R) is true. Vitamin deficiency can indeed cause various diseases. Lack of essential vitamins can lead to a weakened immune system and various health problems. For example, vitamin C deficiency can lead to scurvy, vitamin D deficiency can cause rickets, and vitamin B12 deficiency can result in pernicious anemia. Therefore, Reason (R) is correct.

In conclusion, while vitamin deficiency can lead to diseases, Beri-beri is not a viral infection but rather a nutritional deficiency disease. Hence, option 'C' is the correct answer.

Assertion (A): When a body is dipped in a liquid fully or partially, there is a decrease in its weight.
Reason (R) : The decrease in weight is due to the higher density of the displaced liquid.

The correct answer is option 'C', which states that Assertion (A) is true but Reason (R) is false. Let's understand why.

Explanation:

Density and Weight:
Density is defined as the mass per unit volume of a substance. Weight, on the other hand, is the force exerted by the gravitational pull on an object. Weight depends on the mass of an object and the acceleration due to gravity, whereas density is an intrinsic property of a substance.

When a body is dipped in a liquid:
When a body is dipped in a liquid, there are two main forces acting on it:
1. Buoyant force: This force is exerted by the liquid on the body and is equal to the weight of the liquid displaced by the body.
2. Gravitational force: This force is exerted by the Earth on the body and is equal to the weight of the body.

Effect on weight:
When a body is fully or partially dipped in a liquid, there is a change in its weight. The change in weight depends on the relative densities of the body and the liquid.

If the density of the liquid is greater than the density of the body, the buoyant force exerted by the liquid will be greater than the gravitational force exerted by the Earth. As a result, the net force acting on the body will be upwards, causing a decrease in its weight. This is because the buoyant force partially counteracts the gravitational force.

However, if the density of the body is greater than the density of the liquid, the buoyant force exerted by the liquid will be less than the gravitational force exerted by the Earth. In this case, the net force acting on the body will be downwards, causing an increase in its weight.

Explanation of the Reason (R):
The Reason states that the decrease in weight is due to the higher density of the displaced liquid. This is incorrect because the decrease in weight is actually due to the buoyant force exerted by the liquid, not the density of the displaced liquid.

The buoyant force depends on the volume of the liquid displaced by the body, not the density of the liquid. The density of the displaced liquid only affects the magnitude of the buoyant force, not its direction. Therefore, the Reason (R) is false.

Conclusion:
In conclusion, Assertion (A) is true because there is a decrease in the weight of a body when it is fully or partially dipped in a liquid. However, the Reason (R) is false because the decrease in weight is due to the buoyant force exerted by the liquid, not the density of the displaced liquid.