UPSC CAPF Archives

21. Which one of the following is an example of endothermic reaction?

Which one of the following is an example of endothermic reaction?

CaO(s) + H₂O(l) → Ca(OH)₂(aq)

CaCO₃(s) → CaO(s) + CO₂(g)

C(s) + O₂(g) → CO₂(g)

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

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The correct answer is B) CaCO₃(s) → CaO(s) + CO₂(g).

An endothermic reaction is a reaction that absorbs heat from its surroundings.
A) CaO(s) + H₂O(l) → Ca(OH)₂(aq) (Slaking of lime) is a highly exothermic reaction, releasing significant heat.
B) CaCO₃(s) → CaO(s) + CO₂(g) (Decomposition of calcium carbonate) requires heating to occur, meaning it absorbs heat from the surroundings, making it an endothermic reaction.
C) C(s) + O₂(g) → CO₂(g) (Combustion of carbon) is an exothermic reaction, releasing heat and light.
D) CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) (Combustion of methane) is an exothermic reaction, releasing a large amount of heat.

Exothermic reactions have a negative enthalpy change (ΔH < 0), while endothermic reactions have a positive enthalpy change (ΔH > 0). Decomposition reactions often require energy input to break chemical bonds, making them endothermic. Combustion reactions always release energy, making them exothermic.

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22. Which one of the following is not a breakdown product of glucose dur

Which one of the following is not a breakdown product of glucose during respiration?

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Ethanol

Lactic acid

Water

Methanol

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The correct answer is D) Methanol.

Cellular respiration is the process by which glucose is broken down to release energy. This process begins with glycolysis, which converts glucose into pyruvate. Depending on the presence of oxygen, pyruvate can be further metabolized:
1. Aerobic respiration (in the presence of oxygen): Pyruvate is completely oxidized to carbon dioxide (CO₂) and water (H₂O).
2. Anaerobic respiration (fermentation, in the absence of oxygen): Pyruvate is converted into products like ethanol and carbon dioxide (in yeast and plants) or lactic acid (in muscle cells and some bacteria).
Ethanol, lactic acid, and water are all potential breakdown products of glucose during respiration. Methanol is not produced during the standard biological breakdown of glucose.

Methanol (CH₃OH) is a simple alcohol. It is produced industrially or by anaerobic metabolism of certain bacteria, but not as a standard product of glucose respiration in humans or most common organisms.

23. Which one of the following diseases does not transmit through fine d

Which one of the following diseases does not transmit through fine droplets coming out from mouth or nose of an infected person?

Pneumonia

COVID-19

HIV-AIDS

Tuberculosis

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UPSC CAPF – 2021

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The correct answer is C) HIV-AIDS.

HIV (Human Immunodeficiency Virus), which causes AIDS (Acquired Immunodeficiency Syndrome), is primarily transmitted through specific bodily fluids: blood, semen, vaginal secretions, rectal fluids, and breast milk. The most common modes of transmission are sexual contact, sharing contaminated needles, and mother-to-child transmission during pregnancy, childbirth, or breastfeeding. It is NOT transmitted through casual contact or respiratory droplets like coughing or sneezing. Pneumonia and Tuberculosis are bacterial or viral infections often spread through airborne droplets expelled when an infected person coughs, sneezes, or talks. COVID-19 is a viral disease (caused by SARS-CoV-2) primarily spread through respiratory droplets.

Understanding the modes of transmission is crucial for implementing effective prevention strategies for infectious diseases. Respiratory illnesses are often transmitted via droplets or aerosols, while diseases like HIV are transmitted via specific fluid exchange.

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24. Which one of the following organisms belongs to the kingdom Monera?

Which one of the following organisms belongs to the kingdom Monera?

Diatom

Euglena

Anabaena

Ulothrix

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The correct answer is C) Anabaena.

In the five-kingdom classification system (proposed by R.H. Whittaker), the kingdom Monera includes all prokaryotic organisms. This primarily consists of bacteria and cyanobacteria (formerly known as blue-green algae). Anabaena is a genus of filamentous cyanobacteria, and therefore belongs to the kingdom Monera. Diatoms and Euglena are eukaryotic single-celled organisms belonging to the kingdom Protista. Ulothrix is a filamentous green alga, which is eukaryotic and typically classified under the kingdom Plantae or Protista, but not Monera.

The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. Monerans lack a true nucleus and membrane-bound organelles. Protists are eukaryotic unicellular organisms. Fungi are eukaryotic heterotrophic organisms. Plants are eukaryotic autotrophic organisms. Animals are eukaryotic heterotrophic, multicellular organisms.

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25. Which one of the following is not a connective tissue?

Which one of the following is not a connective tissue?

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Ligament

Tendon

Smooth muscle

Cartilage

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UPSC CAPF – 2021

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The correct answer is C) Smooth muscle.

Connective tissues are tissues that support, connect, or separate different types of tissues and organs in the body. Ligaments connect bone to bone, tendons connect muscle to bone, and cartilage is a flexible connective tissue found in joints, ear, nose, etc. All three (Ligament, Tendon, Cartilage) are types of connective tissue. Smooth muscle, however, is a type of muscle tissue, specialized for contraction, and is distinct from connective tissue.

There are four main types of tissues in animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Connective tissue includes bone, blood, adipose tissue, and fibrous connective tissue (like ligaments and tendons) in addition to cartilage. Muscle tissue is classified into skeletal muscle, smooth muscle, and cardiac muscle.

26. Which one of the following plant tissues has large air spaces?

Which one of the following plant tissues has large air spaces?

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Sclerenchyma

Meristem

Collenchyma

Aerenchyma

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UPSC CAPF – 2021

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The question asks for a plant tissue characterized by large air spaces.
Let’s consider the options:
A) Sclerenchyma: This tissue provides mechanical support. It consists of cells with heavily thickened, often lignified walls, and the cells are usually dead at maturity. It does not contain large air spaces.
B) Meristem: Meristematic tissues consist of actively dividing cells involved in plant growth. The cells are small, thin-walled, and densely packed without significant intercellular spaces.
C) Collenchyma: This tissue provides mechanical support to growing parts of the plant. It consists of living cells with unevenly thickened primary cell walls. While there might be small intercellular spaces, they are not characterized by *large* air spaces.
D) Aerenchyma: This is a specialized type of parenchyma tissue that contains extensive intercellular air spaces. The word “aerenchyma” literally means “air tissue”. These air spaces facilitate gas exchange in plants growing in low-oxygen environments (like wetlands) and provide buoyancy to aquatic plants.
Therefore, Aerenchyma is the plant tissue with large air spaces.

– Understand the structure and function of different types of plant tissues.
– Recognize that aerenchyma is a specialized tissue adapted for gas exchange and buoyancy due to its large air spaces.
– Distinguish aerenchyma from other support tissues like sclerenchyma and collenchyma, and growth tissue like meristem.

Aerenchyma is often found in the stems and roots of aquatic plants (hydrophytes) and plants in marshy or waterlogged soils. It is a modification of parenchyma tissue, which is the most common type of ground tissue in plants.

27. Which one of the following organelles is not found in animal cells?

Which one of the following organelles is not found in animal cells?

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Cell membrane

Endoplasmic reticulum

Cell wall

Lysosome

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UPSC CAPF – 2021

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The question asks which of the listed organelles is *not* found in animal cells. Let’s review each option:
A) Cell membrane: The cell membrane is the outer boundary of animal cells and is present in all eukaryotic cells, including plant cells (where it is inside the cell wall).
B) Endoplasmic reticulum: The endoplasmic reticulum (ER) is a network of membranes involved in protein synthesis (rough ER) and lipid synthesis (smooth ER). It is found in both animal and plant cells.
C) Cell wall: The cell wall is a rigid outer layer that provides structural support, protection, and shape to the cell. Cell walls are present in plant cells (made primarily of cellulose), fungi, bacteria, and some protists, but they are *absent* in animal cells.
D) Lysosome: Lysosomes are membrane-bound organelles containing digestive enzymes. They are primarily found in animal cells, where they are involved in breaking down waste materials and cellular debris. While some plant cells may have vacuoles with lytic activity similar to lysosomes, dedicated lysosomes as found in animal cells are generally considered absent in plant cells. However, the cell wall is definitively absent in animal cells, making it the correct answer.

– Recall the key organelles found in typical animal and plant cells.
– Note the distinguishing features between plant and animal cells, such as the presence of a cell wall, chloroplasts, and large central vacuoles in plants, and lysosomes and centrioles typically in animals.
– The cell wall is a defining feature of plant cells that is absent in animal cells.

Other organelles typically found in animal cells but not in plant cells include centrioles. Organelles typically found in plant cells but not in animal cells include cell walls (as mentioned), chloroplasts, and often a large central vacuole. Both cell types have cell membranes, nuclei, mitochondria, endoplasmic reticulum, Golgi apparatus, and ribosomes.

28. Which one of the following statements with regard to a short-sighted p

Which one of the following statements with regard to a short-sighted person is correct?

A short-sighted person sees the near objects blurred but distant objects clearly and a convex lens is used to correct this defect.

A short-sighted person sees the near objects clearly but distant objects blurred and a concave lens is used to correct this defect.

A short-sighted person sees the near objects blurred but distant objects clearly and a concave lens is used to correct this defect.

A short-sighted person sees the near objects clearly but distant objects blurred and a convex lens is used to correct this defect.

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UPSC CAPF – 2021

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Short-sightedness is medically known as Myopia.
A person with myopia has difficulty seeing distant objects clearly, while they can see near objects clearly. This occurs because the eye converges distant light rays too strongly, causing the image to form in front of the retina instead of on the retina.
To correct myopia, a diverging lens (concave lens) is used. A concave lens spreads out the light rays slightly before they enter the eye, reducing the overall convergence and allowing the image of distant objects to be focused correctly on the retina.
Let’s examine the options:
A) States near objects are blurred and distant objects are clear, which is the opposite of myopia (this describes hyperopia or long-sightedness).
B) States near objects are clear and distant objects are blurred, which correctly describes myopia, and also correctly states that a concave lens is used for correction.
C) States near objects are blurred and distant objects are clear (hyperopia), and suggests a concave lens (corrects myopia). Incorrect combination.
D) States near objects are clear and distant objects are blurred (myopia), but suggests a convex lens (corrects hyperopia). Incorrect lens.

– Understand the definition and symptoms of short-sightedness (Myopia).
– Know the type of lens (converging/convex or diverging/concave) used to correct Myopia.
– Myopia: Near objects clear, distant objects blurred. Image forms in front of retina. Corrected by concave lens.
– Hyperopia: Near objects blurred, distant objects clear. Image forms behind retina. Corrected by convex lens.

The power of a lens used to correct myopia is negative, which corresponds to a concave lens. The power needed depends on the severity of the myopia. Myopia can be caused by an eyeball that is too long or a cornea/lens that is too curved.

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29. An object is placed 10 cm in front of a lens. The image formed is real

An object is placed 10 cm in front of a lens. The image formed is real, inverted and of same size as the object. What is the focal length and nature of the lens?

5 cm, converging

10 cm, diverging

20 cm, converging

20 cm, diverging

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UPSC CAPF – 2021

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An object is placed 10 cm in front of a lens. So, object distance u = 10 cm.
The image formed is real, inverted, and of the same size as the object.
A real and inverted image is formed by a converging lens (convex lens). Diverging lenses (concave lenses) always produce virtual, erect, and diminished images.
For a lens, the magnification (m) is given by the ratio of image distance (v) to object distance (u), with a sign convention: m = v/u for erect images and m = -v/u for inverted images.
Since the image is inverted, m = -v/u.
The image is of the same size as the object, so the magnitude of magnification |m| = 1.
Thus, m = -1.
-v/u = -1 => v = u.
Given u = 10 cm, so v = 10 cm.
Using the lens formula (thin lens equation): 1/f = 1/v – 1/u.
Applying the sign convention: object distance u is typically taken as negative when placed in front of the lens, so u = -10 cm. The image is real and formed on the opposite side of the lens from the object, so image distance v is positive, v = +10 cm.
1/f = 1/(+10 cm) – 1/(-10 cm)
1/f = 1/10 + 1/10
1/f = 2/10
1/f = 1/5
f = 5 cm.
The focal length is positive (f > 0), which confirms that the lens is a converging lens (convex lens).
Alternatively, for a converging lens, a real image of the same size as the object is formed only when the object is placed at a distance of 2f from the lens, and the image is also formed at 2f on the other side. So, u = 2f.
Given u = 10 cm, 10 cm = 2f => f = 5 cm.
The nature of the lens is converging.

– Identify the nature of the lens based on the image characteristics (real, inverted implies converging).
– Use the magnification information (same size implies |m|=1) and image type (inverted implies m=-1) to relate object and image distances (v=u).
– Apply the lens formula (1/f = 1/v – 1/u) with appropriate sign conventions or use the special case rule for an image of the same size formed by a converging lens (object at 2f).
– Determine the sign of the focal length to confirm the nature of the lens (positive f for converging).

For a converging lens (convex lens):
– Object at infinity: real, inverted, point image at F.
– Object beyond 2F: real, inverted, diminished image between F and 2F.
– Object at 2F: real, inverted, same size image at 2F.
– Object between F and 2F: real, inverted, magnified image beyond 2F.
– Object at F: real, inverted, image at infinity.
– Object between the lens and F: virtual, erect, magnified image on the same side as the object.
The condition “real, inverted, and of same size” is unique to the object being placed at 2F for a converging lens.

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30. Which electromagnetic radiation(s) is/are used to cook food?

Which electromagnetic radiation(s) is/are used to cook food?

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Infrared radiation only

Microwave radiation only

Infrared and microwave radiations

All electromagnetic radiations

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UPSC CAPF – 2021

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Electromagnetic radiation is used in various forms for cooking food. Common examples include:
– Microwave ovens use microwave radiation to heat food. Microwaves are absorbed by water, fats, and sugars, causing them to vibrate and produce heat.
– Conventional ovens and grills use infrared radiation (thermal radiation) emitted by heating elements or flames to heat the food surface, and then heat is transferred into the food by conduction and convection.
Therefore, both infrared and microwave radiations are used in cooking. While visible light and other forms of EM radiation also carry energy and can potentially heat things, infrared and microwave are the primary forms utilized in common cooking appliances.

– Understand the different forms of electromagnetic radiation.
– Identify which forms of EM radiation are used in common cooking methods and appliances.
– Microwave ovens use microwaves.
– Ovens and grills use infrared radiation.

The electromagnetic spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays, in order of increasing frequency and energy. Cooking methods primarily utilize the energy transfer mechanisms of infrared radiation (heating surfaces) and microwave radiation (volumetric heating of polar molecules).