UPSC NDA-2 Archives

21. Ammonia (NH 3 ) obtained from different sources always has same propor

Ammonia (NH₃) obtained from different sources always has same proportion of Nitrogen and Hydrogen. It proves the validity of law of:

Reciprocal proportion

Constant proportion

Multiple proportions

None of the above

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UPSC NDA-2 – 2015

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The statement “Ammonia (NH₃) obtained from different sources always has same proportion of Nitrogen and Hydrogen” is a direct application of the Law of Constant Proportions (also known as the Law of Definite Proportions). This law states that a given chemical compound always contains its component elements in fixed proportion by mass, regardless of the source or method of preparation.

The Law of Constant Proportions explains why the elemental composition of a specific compound is always the same.

The Law of Reciprocal Proportion relates the masses of two elements that combine separately with a fixed mass of a third element. The Law of Multiple Proportions states that if two elements can combine to form more than one compound, then the masses of one element that combine with a fixed mass of the other element are in the ratio of small whole numbers. The given statement specifically addresses the fixed composition of a single compound, which is the domain of the Law of Constant Proportions.

22. Identify the place that is not an oil field:

Identify the place that is not an oil field:

Naharkatiya

Kalol

Ledo

Ankleshwar

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UPSC NDA-2 – 2015

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Ledo is primarily known for its coal mining history and railway connection. It is a town in Assam. While the region around Assam is rich in oil, Ledo itself is not identified as a major oil field. Naharkatiya and Kalol are significant oil fields in Assam and Gujarat, respectively. Ankleshwar is also a prominent oil field in Gujarat.

The question tests knowledge of prominent oil fields in India and the ability to identify a place not known primarily for oil extraction.

Major oil fields in India include onshore fields like Digboi, Naharkatiya, Moran-Hugrijan, Rudrasagar, Lakwa (all in Assam); Ankleshwar, Kalol, Mehsana, Nawagam (all in Gujarat); and offshore fields like Mumbai High, Bassein, and Aliabet.

23. Which one of the following statements is not correct?

Which one of the following statements is not correct?

The radius of curvature of a concave mirror is twice its focal length

Power of a convex lens is negative and that of a concave lens is positive

The radius of curvature of a plane mirror is infinity

When a ray of light passes from an optically denser medium to an optically rarer medium, the angle of refraction is greater than the corresponding angle of incidence

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The correct answer is B. The statement about the power of convex and concave lenses is incorrect.

– Statement A is correct. For a spherical mirror, the radius of curvature (R) is twice the focal length (f), i.e., R = 2f.
– Statement B is incorrect. The power of a lens (P = 1/f) is positive for a converging lens (convex lens) because its focal length (f) is positive. The power of a diverging lens (concave lens) is negative because its focal length (f) is negative.
– Statement C is correct. A plane mirror can be considered as a part of a spherical mirror with an infinite radius of curvature. Consequently, its focal length (f = R/2) is also infinite.
– Statement D is correct. According to Snell’s Law, when light travels from a denser medium (higher refractive index n₁) to a rarer medium (lower refractive index n₂), it bends away from the normal. This means the angle of refraction (θ₂) is greater than the angle of incidence (θ₁), as n₁ sin θ₁ = n₂ sin θ₂ and n₁ > n₂, implies sin θ₂ > sin θ₁, leading to θ₂ > θ₁.

The power of a lens is a measure of its ability to converge or diverge light rays. It is expressed in dioptres (D), where 1 D = 1 m⁻¹. Convex lenses are used to correct hypermetropia (long-sightedness), and concave lenses are used to correct myopia (short-sightedness).

24. In case of a compound microscope which of the following statements is

In case of a compound microscope which of the following statements is / are correct?

1. The focal length of the eye piece is larger than the focal length of the objective
2. The focal length of the eye piece is smaller than the focal length of the objective
3. The image produced in a normal optical microscope is real
4. The image produced in a normal optical microscope is virtual

Select the correct answer using the code given below:

1 only

1 and 4

2 and 3

2 and 4

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The correct answer is B. Statements 1 and 4 are correct for a compound microscope.

– Statement 1 is correct. In a compound microscope, the objective lens typically has a very short focal length to produce a highly magnified intermediate image. The eyepiece lens acts as a magnifying glass for this intermediate image and usually has a longer focal length than the objective.
– Statement 2 is incorrect. The focal length of the eyepiece is typically larger than that of the objective.
– Statement 3 is incorrect. The final image produced by a compound microscope and viewed by the observer is a virtual image. The objective lens forms a real intermediate image, but the eyepiece forms a virtual image of this intermediate image.
– Statement 4 is correct. The final image observed through the eyepiece of a compound microscope is virtual, magnified, and inverted relative to the original object.

A compound microscope uses two lens systems to achieve high magnification. The total magnification is the product of the magnification of the objective and the eyepiece. The intermediate image formed by the objective is real, magnified, and inverted, located within the focal length of the eyepiece. The eyepiece then produces a final, further magnified, virtual, and inverted image.

25. Addition of gypsum to cement:

Addition of gypsum to cement:

reduces setting time of cement

produces very light colour cement

increases setting time of cement

shining surface is formed

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UPSC NDA-2 – 2015

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The correct answer is C. Addition of gypsum to cement increases the setting time of cement.

– Cement clinker, when mixed with water, undergoes rapid hydration reactions, especially involving tricalcium aluminate (C₃A), which can lead to flash setting (very rapid hardening).
– Gypsum (calcium sulfate dihydrate) is added to the cement clinker during grinding to act as a retarder.
– Gypsum reacts with C₃A to form ettringite, which precipitates on the surface of the C₃A particles, forming a barrier that slows down the rapid hydration of C₃A.
– This allows sufficient time for the cement paste or concrete to be mixed, transported, placed, and finished before it begins to harden.

The amount of gypsum added is carefully controlled (typically 2-5% by weight of clinker) as too little or too much can adversely affect the setting properties and strength development of the cement.

26. The Manas National Park is situated in the State of:

The Manas National Park is situated in the State of:

Madhya Pradesh

Jharkhand

Assam

West Bengal

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UPSC NDA-2 – 2015

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The correct answer is C. The Manas National Park is situated in the State of Assam.

– Manas National Park is located in the foothills of the Himalayas in Assam, India.
– It is a UNESCO World Heritage Site, a Project Tiger Reserve, an Elephant Reserve, and a Biosphere Reserve.
– The park is famous for its rare and endangered endemic wildlife such as the Assam roofed turtle, hispid hare, golden langur, and pygmy hog. It is also home to wild water buffaloes, tigers, elephants, and rhinos.

Assam is known for its rich biodiversity and several national parks and wildlife sanctuaries, including Kaziranga National Park (famous for one-horned rhinoceroses), Nameri National Park, Orang National Park, and Dibru-Saikhowa National Park.

27. The silvering in thermos flasks is done to avoid heat transfer by:

The silvering in thermos flasks is done to avoid heat transfer by:

Convection

Conduction

Radiation

Both convection and conduction

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The correct answer is C. The silvering in thermos flasks is done to avoid heat transfer by radiation.

– A thermos flask is designed to minimize heat transfer through all three mechanisms: conduction, convection, and radiation.
– The vacuum between the double walls reduces heat transfer by conduction and convection.
– The stopper reduces convection (and some conduction).
– The silvered surfaces (typically vacuum-deposited aluminum) on the inner and outer walls are poor emitters and excellent reflectors of thermal radiation. This significantly reduces heat transfer by radiation across the vacuum.

Thermal radiation is heat transferred in the form of electromagnetic waves. Shiny, reflective surfaces are effective at minimizing radiation transfer because they absorb very little and reflect most of the incident radiation.

28. Living things are grouped into subgroups like plant kingdom / animal k

Living things are grouped into subgroups like plant kingdom / animal kingdom. Which one of the following is not correct for animal kingdom?

Cannot make their own food

Body contains cellulose

Do not have chlorophyll

Migrate from one place to another

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The correct answer is B. Animal bodies do not contain cellulose as a structural component.

– Statement A is correct: Animals are heterotrophs; they cannot produce their own food and obtain energy by consuming other organisms.
– Statement B is incorrect: Cellulose is a complex carbohydrate that is the main structural component of cell walls in plants. Animal cells do not have cell walls, and their bodies are not primarily composed of cellulose. Some animals (like termites) can digest cellulose with the help of symbiotic microorganisms, but their bodies themselves do not contain it structurally.
– Statement C is correct: Animals lack chlorophyll, the pigment necessary for photosynthesis, unlike plants.
– Statement D is generally correct: Most animals are motile, meaning they can move from one place to another, which is a key characteristic distinguishing them from sessile plants (though some animals are sessile, like sponges).

The animal kingdom (Kingdom Animalia) is characterized by eukaryotic, multicellular organisms that are heterotrophic and typically develop from an embryo. Key characteristics include lack of cell walls, presence of nervous tissue and muscle tissue (in most), and mobility (in most).

29. Consider the following reaction: CH₄(g) + H₂O(g) 1270 K CO(g) + 3

Consider the following reaction:
CH₄(g) + H₂O(g)

1270 K

CO(g) + 3H₂(g)
In the reaction given above, the mixture of CO and H₂, is:

natural gas

water gas

producer gas

industrial gas

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The correct answer is B. The mixture of CO and H₂ produced by the steam reforming of methane is known as water gas.

– The reaction CH₄(g) + H₂O(g) → CO(g) + 3H₂(g) is called steam reforming of methane.
– The resulting mixture of carbon monoxide (CO) and hydrogen (H₂) is commonly referred to as synthesis gas or, specifically when produced via steam reactions with carbonaceous materials or hydrocarbons, water gas.
– Producer gas is formed by reacting carbonaceous fuel with air and steam, containing CO, H₂, N₂, and CO₂.
– Natural gas is primarily methane.

Water gas and synthesis gas are important industrial feedstocks used in the production of various chemicals, including methanol, ammonia, and synthetic fuels (via the Fischer-Tropsch process).

30. Which one of the following is not a sea port?

Which one of the following is not a sea port?

Paradeep

Haldia

Diamond Harbour

Dhamra

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The correct answer is C. Diamond Harbour is not typically classified as a major commercial seaport like the others listed.

– Paradeep is a major seaport located in Odisha.
– Haldia is a major port and industrial complex on the Hooghly River, serving as a port for West Bengal. It is part of the Kolkata Port Trust.
– Dhamra is a major deep-water private port located in Odisha.
– Diamond Harbour is a town on the Hooghly River downstream from Kolkata. While it has some historical significance and limited port-related activities, it is primarily known as a tourist spot and fishing harbour, and not a major commercial sea port in the same league as Paradeep, Haldia, or Dhamra.

India has a coastline of over 7,500 km with numerous major, intermediate, and minor ports handling a vast volume of cargo traffic. The classification of ports depends on factors like capacity, traffic volume, and administrative control.