UPSC NDA-2 Archives

21. Malarial parasite is a

Malarial parasite is a

bacteria

protozoa

virus

fungus

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The malarial parasite, Plasmodium, is a single-celled eukaryotic organism belonging to the phylum Apicomplexa. Organisms in this group are commonly classified as protozoa.

Protozoa are diverse group of unicellular eukaryotic organisms, many of which are motile and include parasitic forms like Plasmodium.

Malaria is caused by the Plasmodium parasite, which is transmitted to humans through the bite of infected female Anopheles mosquitoes. Bacteria are prokaryotic; viruses and fungi are different classes of microorganisms.

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22. In which one of the following, methano- gens, i.e., methane producing

In which one of the following, methano- gens, i.e., methane producing bacteria are not present ?

Rumen of cattle

Aerobic environment

Anaerobic sludge

Excreta of cattle

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Methanogens are a group of anaerobic archaea that produce methane as a metabolic byproduct in anoxic conditions. They are strictly anaerobic, meaning oxygen is toxic to them.

Methanogens thrive in environments where oxygen is absent and organic matter is undergoing decomposition. Examples include the digestive tracts of ruminants (like cattle rumen), anaerobic sludge digesters in wastewater treatment, and sediments in swamps and marshes.

The rumen of cattle is a highly anaerobic environment where methanogens play a crucial role in the digestion of cellulose. Anaerobic sludge in sewage treatment plants is another common habitat. Cattle excreta, being partially digested material from the rumen and exposed to anaerobic conditions during storage, also contains active methanogens. An aerobic environment, however, is unsuitable for methanogens due to the presence of oxygen.

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23. Consider the following statements about cactus : 1. The leaves are r

Consider the following statements about cactus :

1. The leaves are reduced to spines.
2. The stem does the photosynthesis.

Which of the statements given above is/are correct ?

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1 only

2 only

Both 1 and 2

Neither 1 nor 2

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Both statements about cactus adaptations are correct. Cacti are succulents adapted to arid environments. Their leaves are typically reduced to spines to minimize water loss through transpiration and provide defense. The fleshy green stems take over the function of photosynthesis, which is usually carried out by leaves in most plants.

– Statement 1 is correct: Reduction of leaves to spines is a key adaptation of cacti to reduce surface area and thus water loss through transpiration in hot, dry climates. Spines also deter herbivores.
– Statement 2 is correct: Cacti stems contain chlorophyll and are the primary sites of photosynthesis in the absence of significant leaf area. They are also succulent, storing water.

Cacti also have other adaptations for survival in arid environments, such as shallow but extensive root systems to absorb water quickly from rainfall, a waxy cuticle on the stem to reduce evaporation, and CAM photosynthesis, which allows them to keep their stomata closed during the day to conserve water.

24. Combination of one volume of nitrogen with three volumes of hydrogen

Combination of one volume of nitrogen with three volumes of hydrogen produces

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one volume of ammonia

two volumes of ammonia

three volumes of ammonia

one and a half volumes of ammonia

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The reaction between nitrogen and hydrogen to produce ammonia is represented by the balanced chemical equation: N₂(g) + 3H₂(g) → 2NH₃(g). According to Avogadro’s law, at the same temperature and pressure, the ratio of the volumes of reacting gases and gaseous products is equal to the ratio of their stoichiometric coefficients in the balanced equation. Thus, 1 volume of nitrogen reacts with 3 volumes of hydrogen to produce 2 volumes of ammonia.

– The balanced equation for the Haber process is N₂(g) + 3H₂(g) → 2NH₃(g).
– The stoichiometric coefficients are 1 for N₂, 3 for H₂, and 2 for NH₃.
– At constant temperature and pressure, the volume ratio of reacting gases and gaseous products is equal to the mole ratio (and stoichiometric coefficient ratio).

This principle relating volumes of reacting gases to their stoichiometric coefficients is known as Gay-Lussac’s law of combining volumes.

25. Which one of the following has different number of molecules ? (All ar

Which one of the following has different number of molecules ? (All are kept at normal temperature and pressure)

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3 gram of Hydrogen

48 gram of Oxygen

42 gram of Nitrogen

2 gram of Carbon

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To determine which option has a different number of molecules, we need to calculate the number of moles for each substance. The number of molecules is directly proportional to the number of moles (Avogadro’s law states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules; here we are comparing masses).
– A) 3 gram of Hydrogen (H₂): Molar mass ≈ 2 g/mol. Moles = 3 g / 2 g/mol = 1.5 moles.
– B) 48 gram of Oxygen (O₂): Molar mass ≈ 32 g/mol. Moles = 48 g / 32 g/mol = 1.5 moles.
– C) 42 gram of Nitrogen (N₂): Molar mass ≈ 28 g/mol. Moles = 42 g / 28 g/mol = 1.5 moles.
– D) 2 gram of Carbon (C): Molar mass ≈ 12 g/mol. Moles = 2 g / 12 g/mol = 1/6 moles ≈ 0.167 moles.
Options A, B, and C all contain 1.5 moles (and thus the same number of molecules). Option D contains a significantly different number of moles (and thus atoms, as carbon exists as atoms in its elemental solid form).

– The number of molecules in a given mass of a substance is proportional to the number of moles, which is calculated as Mass / Molar Mass.
– Avogadro’s number (approximately 6.022 x 10²³) represents the number of particles (atoms, molecules, etc.) in one mole of a substance.

The condition “All are kept at normal temperature and pressure” (NTP) is relevant for comparing volumes of gases using Avogadro’s law, but here we are comparing masses and thus the number of moles/molecules directly using molar masses. Note that elemental carbon is a solid at NTP, while hydrogen, oxygen, and nitrogen are gases (diatomic molecules H₂, O₂, N₂). The question phrasing “number of molecules” for carbon is slightly imprecise as solid carbon consists of atoms in a lattice, but the underlying principle is comparing the amount of substance (moles).

26. There are six electrons, six protons and six neutrons in an atom of an

There are six electrons, six protons and six neutrons in an atom of an element. What is the atomic number of the element ?

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The atomic number of an element is defined by the number of protons found in the nucleus of an atom of that element. The question states that the atom has six protons. Therefore, the atomic number of the element is 6.

– Atomic Number (Z) = Number of Protons.
– In a neutral atom, Number of Protons = Number of Electrons.
– The mass number is the total number of protons and neutrons in the nucleus (Mass Number = Protons + Neutrons).
– In this case, Protons = 6, Electrons = 6, Neutrons = 6.
– Atomic Number = 6.
– Mass Number = 6 + 6 = 12. This describes an atom of Carbon-12.

The number of neutrons can vary for atoms of the same element, leading to different isotopes. However, the number of protons is unique to each element and determines its identity.

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27. Identify the element having zero valency

Identify the element having zero valency

Sulphur

Phosphorous

Lead

Radon

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Valency is the combining capacity of an element. Elements with zero valency are those that are chemically inert and do not readily form chemical bonds under normal conditions because their outermost electron shell is full. These elements are the noble gases. Among the given options, Radon (Rn) is a noble gas.

– Sulphur (S) typically has valencies of 2, 4, or 6.
– Phosphorous (P) typically has valencies of 3 or 5.
– Lead (Pb) typically has valencies of 2 or 4.
– Radon (Rn) is a noble gas (Group 18 of the periodic table) and its valency is considered zero.

Noble gases (Helium, Neon, Argon, Krypton, Xenon, and Radon) have a stable electron configuration with a full outermost electron shell (except Helium, which has 2 electrons in its single shell), making them very unreactive.

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28. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the Lists :

List I (Process)	List II (Type of change)
A. Heating Camphor	1. Chemical
B. Cooling of water vapour up to room temperature	2. Evaporation
C. Cooking an egg	3. Condensation
D. Formation of water vapour at room temperature	4. Sublimation

Code :

A-4, B-3, C-1, D-2

A-4, B-1, C-3, D-2

A-2, B-1, C-3, D-4

A-2, B-3, C-1, D-4

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Matching the process to the type of change:
– A. Heating Camphor: Camphor changes directly from solid to gas upon heating, a process called sublimation. This is a physical change. (A-4)
– B. Cooling of water vapour up to room temperature: Water vapour (gas) changes into liquid water upon cooling, a process called condensation. This is a physical change. (B-3)
– C. Cooking an egg: Cooking an egg involves the denaturation of proteins, which is an irreversible chemical change where new substances with different properties are formed. (C-1)
– D. Formation of water vapour at room temperature: Liquid water changes into water vapour (gas) at room temperature through evaporation. This is a physical change. (D-2)
The correct match is A-4, B-3, C-1, D-2.

– Physical changes alter the form or appearance of a substance but not its chemical composition (e.g., melting, boiling, freezing, condensation, sublimation, dissolution).
– Chemical changes result in the formation of new substances with different chemical properties (e.g., cooking, burning, rusting, digestion).

Sublimation is a less common phase transition where a substance goes directly from solid to gas without passing through the liquid phase. Deposition is the reverse process (gas to solid).

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29. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the Lists :

List I (River)	List II (Mouth of the river)
A. Danube	1. North sea
B. Rhine	2. Black sea
C. Rhone	3. Bay of Biscay
D. Loire	4. Mediterranean sea

Code :

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A-2, B-1, C-4, D-3

A-3, B-4, C-1, D-2

A-2, B-4, C-1, D-3

A-3, B-1, C-4, D-2

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Matching the rivers to their mouths:
– A. Danube: The Danube flows eastward across central and eastern Europe and empties into the Black Sea. (A-2)
– B. Rhine: The Rhine flows north-west through Western Europe and empties into the North Sea. (B-1)
– C. Rhone: The Rhone flows south through Switzerland and France and empties into the Mediterranean Sea. (C-4)
– D. Loire: The Loire flows west across France and empties into the Bay of Biscay (part of the Atlantic Ocean). (D-3)
The correct match is A-2, B-1, C-4, D-3.

– The Danube is Europe’s second-longest river.
– The Rhine is a major European river and a vital inland waterway.
– The Rhone is a significant river of Switzerland and France.
– The Loire is the longest river in France.

Understanding the major river systems and their destinations (seas, oceans, or other rivers) is important for world geography. River mouths are often characterized by deltas or estuaries, which are ecologically and economically significant.

30. Arrange the following states in order of their decreasing population s

Arrange the following states in order of their decreasing population size as per the census 2011 :

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1. West Bengal
2. Bihar
3. Maharashtra
4. Andhra Pradesh

Select the correct answer using the code given below :

2 – 3 – 1 – 4

3 – 2 – 1 – 4

1 – 4 – 3 – 2

3 – 1 – 4 – 2

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Based on the 2011 Census of India, the population sizes of the given states were approximately:
1. West Bengal: ~91.3 million
2. Bihar: ~104.1 million
3. Maharashtra: ~112.4 million
4. Andhra Pradesh (undivided): ~84.6 million
Arranging these in decreasing order of population: Maharashtra > Bihar > West Bengal > Andhra Pradesh. This corresponds to the sequence 3 – 2 – 1 – 4.

– Maharashtra had the second-largest population in India as per Census 2011 (after Uttar Pradesh).
– Bihar had the third-largest population.
– West Bengal had the fourth-largest population.
– Andhra Pradesh (undivided) had the fifth-largest population.

The Census of India is conducted every 10 years and provides vital demographic data. Population figures can change over time, and state reorganizations (like the bifurcation of Andhra Pradesh into Andhra Pradesh and Telangana in 2014) impact current rankings, but the question specifically refers to the 2011 census data.