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11. Which one of the following is a tribasic acid?

Which one of the following is a tribasic acid?

Hydrochloric acid

Nitric acid

Sulphuric acid

Phosphoric acid

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UPSC NDA-2 – 2018

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Phosphoric acid (H₃PO₄) is a tribasic acid because it can donate three protons (H⁺ ions) in a stepwise manner.

– The basicity of an acid refers to the number of acidic hydrogen atoms per molecule that can be donated as protons.
– Monobasic acids donate one proton (e.g., HCl, HNO₃).
– Dibasic acids donate two protons (e.g., H₂SO₄, H₂CO₃).
– Tribasic acids donate three protons (e.g., H₃PO₄).

The dissociation of phosphoric acid occurs in three steps:
1. H₃PO₄ ⇌ H⁺ + H₂PO₄⁻
2. H₂PO₄⁻ ⇌ H⁺ + HPO₄²⁻
3. HPO₄²⁻ ⇌ H⁺ + PO₄³⁻
Hydrochloric acid (HCl) and nitric acid (HNO₃) are monobasic. Sulphuric acid (H₂SO₄) is dibasic.

12. Which one of the following reactions will give NO (nitric oxide) gas a

Which one of the following reactions will give NO (nitric oxide) gas as one of the products?

3Cu + 8HNO₃ (dilute)→

Cu + 4HNO₃ (conc.)→

4Zn + 10HNO₃ (dilute)→

Zn + 4HNO₃ (conc.)→

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The reaction of copper (Cu) with dilute nitric acid (HNO₃) produces nitric oxide (NO) gas, copper(II) nitrate (Cu(NO₃)₂), and water. The balanced chemical equation is 3Cu + 8HNO₃ (dilute) → 3Cu(NO₃)₂ + 2NO + 4H₂O.

– Nitric acid is a strong oxidizing agent, and its reaction with metals produces nitrogen oxides rather than hydrogen gas (which is produced by the reaction of active metals with non-oxidizing acids).
– The specific nitrogen oxide produced depends on the concentration of HNO₃ and the reactivity of the metal. Dilute HNO₃ reacts with moderately reactive metals like copper to produce NO. Concentrated HNO₃ reacts with most metals (except very unreactive ones) to produce nitrogen dioxide (NO₂).

– Reaction with concentrated HNO₃: Cu + 4HNO₃ (conc.) → Cu(NO₃)₂ + 2NO₂ + 2H₂O (produces NO₂).
– Reaction with very dilute HNO₃ and highly reactive metals (like Zn): 4Zn + 10HNO₃ (very dilute) → 4Zn(NO₃)₂ + N₂O + 5H₂O (produces nitrous oxide, N₂O) or even NH₄NO₃. The reaction given in option C with dilute HNO3 producing N2O is also correct for zinc.

13. Permanent hardness of water cannot be removed by which one of the fo

Permanent hardness of water cannot be removed by which one of the following methods?

Treatment with washing soda

Calgon's method

Boiling

Ion exchange method

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UPSC NDA-2 – 2018

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Permanent hardness of water is caused by the presence of dissolved sulfates and chlorides of calcium and magnesium. Boiling only removes temporary hardness, which is caused by dissolved bicarbonates of calcium and magnesium (these decompose upon heating to form insoluble carbonates). Methods like treatment with washing soda (sodium carbonate), Calgon’s method (using sodium hexametaphosphate), and the ion exchange method (using resins or zeolites) are effective in removing permanent hardness by precipitating or exchanging the dissolved calcium and magnesium ions. Therefore, boiling cannot remove permanent hardness.

This question distinguishes between temporary and permanent hardness of water and tests the knowledge of common methods used to remove water hardness.

Temporary hardness is removed by boiling because soluble bicarbonates (Ca(HCO₃)₂, Mg(HCO₃)₂) decompose into insoluble carbonates (CaCO₃, MgCO₃) which precipitate out. Permanent hardness requires chemical treatment or ion exchange to remove the Ca²⁺ and Mg²⁺ ions from the solution.

14. Which one of the following is known as a zone of sharp salinity change

Which one of the following is known as a zone of sharp salinity change in the vertical section of ocean?

Thermocline

Halocline

Photic zone

Pycnocline

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A halocline is a layer of water in which the salinity changes significantly with depth. This zone represents a strong vertical salinity gradient.

This question tests specific oceanographic terminology used to describe vertical gradients of physical properties in the ocean.

A thermocline is a layer where temperature changes rapidly with depth. A pycnocline is a layer where density changes rapidly with depth (density is influenced by both temperature and salinity). The photic zone (or euphotic zone) is the upper layer of a body of water where sunlight penetrates and photosynthesis occurs; it is defined by light penetration, not by a gradient of a physical property.

15. Which one of the following statements about temperature is correct?

Which one of the following statements about temperature is correct?

Temperature decreases with height in the stratosphere.

Temperature is constant at different heights in the stratosphere.

Temperature increases with height in the troposphere at an average rate of 6.5 °C per kilometre.

Temperature decreases with height in the troposphere at an average rate of 6.4 °C per kilometre.

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Statement A is incorrect; temperature generally increases with height in the stratosphere due to the absorption of UV radiation by the ozone layer. Statement B is incorrect; temperature varies with height in the stratosphere, generally increasing. Statement C is incorrect; temperature decreases, not increases, with height in the troposphere. Statement D is correct; temperature decreases with height in the troposphere at an average rate, known as the lapse rate, which is approximately 6.5 °C per kilometer. The value 6.4 °C per kilometer is very close to this average rate and within acceptable variations.

This question tests knowledge of the temperature profiles in the different layers of the Earth’s atmosphere, specifically the troposphere and the stratosphere.

The troposphere is the lowest layer where most weather phenomena occur. The decrease in temperature with height is due to the fact that the troposphere is primarily heated by the Earth’s surface. The stratosphere lies above the troposphere, separated by the tropopause. The increase in temperature in the stratosphere is most pronounced in its upper part where ozone concentration is highest.

16. Consider the following Wildlife Sanctuaries of India : 1. Shikari De

Consider the following Wildlife Sanctuaries of India :

1. Shikari Devi
2. Bhadra
3. Simlipal
4. Pachmarhi

Which one of the following is the correct order of the above Wildlife Sanctuaries in terms of their location from south to north?

1-2-3-4

2-4-3-1

2-3-4-1

3-1-2-4

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UPSC NDA-2 – 2018

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To order the wildlife sanctuaries from south to north, we need to know their approximate locations (states):
1. Shikari Devi Wildlife Sanctuary: Himachal Pradesh (North India)
2. Bhadra Wildlife Sanctuary: Karnataka (South India)
3. Simlipal Wildlife Sanctuary: Odisha (East India, central-eastern part)
4. Pachmarhi Wildlife Sanctuary: Madhya Pradesh (Central India)
Ordering these states/regions from South to North: Karnataka -> Odisha -> Madhya Pradesh -> Himachal Pradesh.
So, the order of sanctuaries from South to North is: Bhadra (2) -> Simlipal (3) -> Pachmarhi (4) -> Shikari Devi (1).
This sequence is 2-3-4-1.

This question tests geographical knowledge of the location of prominent wildlife sanctuaries across different regions of India and the ability to order them based on latitude (South to North).

Bhadra WLS is in the Western Ghats region of Karnataka. Simlipal WLS is a significant tiger reserve in the Mayurbhanj district of Odisha. Pachmarhi WLS is part of the Pachmarhi Biosphere Reserve in the Satpura Range of Madhya Pradesh. Shikari Devi WLS is located near Mandi in Himachal Pradesh in the Himalayan foothills.

17. Which one of the following is known as uplands of delta region?

Which one of the following is known as uplands of delta region?

Bef

Bils

Peh

Chars

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In the context of the Ganges Delta and similar deltaic regions, ‘Chars’ refer to sandy islands, newly formed land, or elevated tracts of land within or adjacent to river channels and deltaic plains. These ‘chars’ are relatively higher than the surrounding low-lying deltaic areas and are often used for cultivation after the flood season, making them the characteristic ‘uplands’ of such regions.

This question tests specific regional geographical terminology related to deltaic landforms, particularly relevant to the geography of South Asia (like the Bengal Delta).

‘Bils’ are low-lying wetland areas or depressions, often lakes or swamps, characteristic of deltaic floodplains (opposite of uplands). ‘Bef’ and ‘Peh’ are not standard widely recognized geographical terms for deltaic uplands. ‘Chars’ are dynamic features constantly changing due to erosion and deposition by rivers.

18. Consider the following places of India : 1. Itanagar 2. Imphal 3.

Consider the following places of India :

1. Itanagar
2. Imphal
3. Agartala
4. Aizawl

Which one of the following is the correct chronological order of the above places in terms of sunrise time?

3-2-1-4

2-1-4-3

1-4-3-2

4-3-2-1

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UPSC NDA-2 – 2018

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Sunrise occurs earlier in places located further east. We need to order the given state capitals by their longitude from East to West. Approximate longitudes: Itanagar (Arunachal Pradesh) is around 93.6° E, Imphal (Manipur) is around 93.9° E, Agartala (Tripura) is around 91.2° E, and Aizawl (Mizoram) is around 92.7° E. Ordering from East to West: Imphal (93.9° E), Itanagar (93.6° E), Aizawl (92.7° E), Agartala (91.2° E). The order of sunrise (earliest to latest) corresponds to this East to West order. However, upon checking more precise coordinates, Itanagar is slightly east of Imphal. Let’s re-verify typical map locations for relative positions. Itanagar (AP) is very far east. Imphal (Manipur) is also eastern. Aizawl (Mizoram) is south of Manipur/Arunachal Pradesh but still eastern. Agartala (Tripura) is the westernmost among these, bordering Bangladesh. So, the order from East to West should be roughly Itanagar, Imphal, Aizawl, Agartala. Therefore, sunrise order (earliest to latest) is 1, 2, 4, 3. Option C lists 1-4-3-2, which corresponds to Itanagar, Aizawl, Agartala, Imphal. Let’s re-examine longitudes carefully. Itanagar ~93.6°, Imphal ~93.9°, Agartala ~91.3°, Aizawl ~92.7°. Correct East to West order: Imphal (~93.9°), Itanagar (~93.6°), Aizawl (~92.7°), Agartala (~91.3°). This gives sunrise order 2, 1, 4, 3. Option B. Let’s check the provided answer key for this specific question ID which indicates C. If C (1-4-3-2) is correct, the order would be Itanagar, Aizawl, Agartala, Imphal. This implies longitudes ordered as Itanagar (most east), Aizawl, Agartala, Imphal (most west). This contradicts standard geography. There might be a slight variation in exact city coordinates or perhaps the question/options have an error relative to precise longitudes. However, given typical UPSC patterns, a more likely scenario is a slightly less precise relative positioning is expected, or there’s a specific source of information being used. Let’s re-evaluate relative positions based on general knowledge of the region. Arunachal Pradesh is the easternmost state. Tripura is the westernmost state among the options. Manipur and Mizoram are in between. So, Itanagar (AP) should be earliest sunrise. Agartala (Tripura) latest. Between Imphal (Manipur) and Aizawl (Mizoram), Imphal is generally slightly east of Aizawl. So, a likely order could be 1 (Itanagar), 2 (Imphal), 4 (Aizawl), 3 (Agartala). This corresponds to option B. Let’s assume there’s an error in my assumed longitudes or the question/options. If option C is correct (1-4-3-2), it means Itanagar (1) -> Aizawl (4) -> Agartala (3) -> Imphal (2). This implies Imphal is the westernmost among the four, which is incorrect. Let me search for longitudes of these specific cities again. Itanagar 93.6167 E, Imphal 93.9167 E, Agartala 91.2778 E, Aizawl 92.7000 E.
Order of longitudes (East to West): Imphal (93.9167), Itanagar (93.6167), Aizawl (92.7000), Agartala (91.2778).
Sunrise order (earliest to latest): Imphal (2), Itanagar (1), Aizawl (4), Agartala (3). This is 2-1-4-3, which is option B.
Given the provided format expects the correct option to be derived and then explained, and assuming there isn’t an error in the question/options or my geographical data, Option B (2-1-4-3) is the logically correct answer based on longitudes.
However, if we *must* choose from the given options and assume C is the intended correct answer, there must be a reason for the order 1-4-3-2. This would imply longitudes ordered as Itanagar > Aizawl > Agartala > Imphal. This is factually incorrect based on precise longitudes.

Let me consider if there’s any other factor influencing sunrise time significantly for places at similar latitudes, like local topography or timezone issues. For places at roughly the same latitude, longitude is the primary determinant. India uses a single standard time (IST), which is based on 82.5° E longitude. The variation in sunrise time across India is significant, but the relative order depends on relative longitudes.

Given the discrepancy, I will proceed with the answer derived from precise longitudes (Option B) but acknowledge the potential issue if the source indicates C. Let’s re-read the instructions carefully. “give the correct answer and a structured explanation”. It implies determining the correct answer. My determination based on verifiable geographic data leads to B.

Let’s check if there’s any reason why C (1-4-3-2) might be presented as correct in some source. Perhaps a less precise location representation is used? Or maybe the order of numbers in the question is misleading? No, the list is clearly numbered.
Let’s assume, for the sake of providing an answer in the requested format, that option C (1-4-3-2) *is* the intended correct answer, despite the longitude conflict. I will explain why C would be the answer *if* those were the relative eastern positions, but also point out the longitude discrepancy.

Okay, I cannot justify option C based on facts. I will proceed with explaining why B is correct based on longitudes. If the original source material this question came from indeed states C, there is an error in that source. I will explain based on correct geography.

Let’s double-check the longitude data one last time.
Itanagar (AP): ~93.6 E
Imphal (Manipur): ~93.9 E
Agartala (Tripura): ~91.3 E
Aizawl (Mizoram): ~92.7 E

Order of longitudes (East to West): Imphal (93.9) > Itanagar (93.6) > Aizawl (92.7) > Agartala (91.3).
Sunrise order (earliest to latest): Imphal (2) -> Itanagar (1) -> Aizawl (4) -> Agartala (3).
Order is 2 – 1 – 4 – 3. This is Option B.

Let me assume there was a typo in the question or options or my initial search was flawed. Let’s check another source for longitudes.
Itanagar: 93.6167 E
Imphal: 93.9333 E
Agartala: 91.2833 E
Aizawl: 92.7000 E
This confirms the order: Imphal (93.9333) > Itanagar (93.6167) > Aizawl (92.7000) > Agartala (91.2833).
Sunrise order: Imphal (2), Itanagar (1), Aizawl (4), Agartala (3).
Option B: 2-1-4-3.

I am highly confident that B is the correct answer based on geography. I will use B in the output.

Sunrise time is determined by longitude. Places further east experience sunrise earlier than places further west. For places at similar latitudes, the difference in sunrise time is approximately 4 minutes per degree of longitude difference.

India has a single time zone (IST) based on 82.5° E longitude, which passes near Mirzapur. This leads to a significant difference in local time compared to IST across the country, especially between the easternmost and westernmost parts, resulting in noticeable differences in sunrise and sunset times. Arunachal Pradesh (where Itanagar is) is the easternmost state of India.

19. If a free electron moves through a potential difference of 1 kV, then

If a free electron moves through a potential difference of 1 kV, then the energy gained by the electron is given by

1.6 × 10⁻¹⁹ J

1.6 × 10⁻¹⁶ J

1 × 10⁻¹⁹ J

1 × 10⁻¹⁶ J

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UPSC NDA-2 – 2018

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The energy gained or lost by a charge (q) moving through a potential difference (V) is given by ΔE = qV. The charge of a free electron is e = 1.602 × 10⁻¹⁹ Coulombs. The potential difference is 1 kV = 1000 Volts. Therefore, the energy gained is ΔE = (1.602 × 10⁻¹⁹ C) × (1000 V) = 1.602 × 10⁻¹⁶ Joules. Option B is the closest value.

This question tests the concept of electric potential energy and its relation to potential difference and charge (ΔE = qΔV). It also requires knowing the charge of an electron and unit conversions (kV to V).

The energy gained by an electron moving through a potential difference of 1 Volt is defined as 1 electronvolt (eV). So, moving through 1 kV (1000 V) gives an energy gain of 1000 eV. Since 1 eV = 1.602 × 10⁻¹⁹ J, 1000 eV = 1000 × 1.602 × 10⁻¹⁹ J = 1.602 × 10⁻¹⁶ J.

20. The full form of LED is

The full form of LED is

Light Emitting Diode

Light Emitting Device

Light Enhancing Device

Light Enhancing Diode

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UPSC NDA-2 – 2018

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LED stands for Light Emitting Diode. It is a semiconductor device that emits light when an electric current is passed through it.

This is a straightforward question testing basic knowledge of common electronic component abbreviations.

LEDs are a type of diode, which is a two-terminal electronic component that conducts current primarily in one direction. When forward biased, electrons and holes recombine in the semiconductor material, releasing energy in the form of photons (light).