UPSC CDS-1 Archives

11. Which one among the following stars is nearest to the earth?

Which one among the following stars is nearest to the earth?

Sirius

Arcturus

Spica

Proxima Centauri

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The correct option is D.

Among the options provided, Proxima Centauri is the star nearest to the Earth (excluding the Sun). It is a red dwarf star located about 4.24 light-years away, part of the Alpha Centauri star system.

Sirius is the brightest star in the night sky, located about 8.6 light-years away. Arcturus is a bright giant star about 37 light-years away. Spica is a binary star system and one of the brightest stars, located about 250 light-years away.

12. The monomer/monomers used for the synthesis of Nylon 6 is/are

The monomer/monomers used for the synthesis of Nylon 6 is/are

hexamethylenediamine and adipic acid

caprolactam

urea and formaldehyde

phenol and formaldehyde

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The correct option is B.

Nylon 6 is synthesized through the ring-opening polymerization of caprolactam. Caprolactam is a cyclic amide (lactam) with six carbon atoms. Upon heating, the ring opens, and the linear molecules polymerize.

Option A, hexamethylenediamine and adipic acid, are the monomers for Nylon 6,6, which is formed by condensation polymerization. Option C, urea and formaldehyde, react to form urea-formaldehyde resin. Option D, phenol and formaldehyde, react to form phenol-formaldehyde resin (Bakelite).

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

Which one of the following statements is not correct?

Fischer projection represents the molecule in an eclipsed conformation.

Newman projection can be presented in eclipsed, staggered and skew conformations.

Fischer projection of the molecule is its most stable conformation.

In Sawhorse projections, the lines are inclined at an angle of 120° to each other.

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The correct option is C.

Fischer projections represent molecules in a specific orientation equivalent to an eclipsed conformation, where substituent groups on adjacent carbon atoms are aligned. Eclipsed conformations are generally higher in energy and less stable than staggered conformations due to torsional strain. The most stable conformation for a molecule is usually a staggered conformation (specifically, anti-staggered when possible), not the eclipsed conformation depicted by a Fischer projection.

Newman projections allow visualization of different conformations (eclipsed, staggered, skew) by looking down a specific bond. Sawhorse projections also depict molecules from an angle showing the relationship between groups on adjacent carbons, and the lines are often drawn to illustrate spatial arrangement, sometimes with angles around 120° to represent the tetrahedral geometry around carbon atoms in a planar projection.

14. In which of the following, functional group isomerism is not possible?

In which of the following, functional group isomerism is not possible?

Alcohols

Aldehydes

Alkyl halides

Cyanides

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The correct option is C.

Functional group isomerism involves compounds with the same molecular formula but different functional groups. Alcohols and ethers are functional group isomers (e.g., ethanol and dimethyl ether). Aldehydes and ketones are functional group isomers (e.g., propanal and propanone). Cyanides and isocyanides are functional group isomers (e.g., methyl cyanide and methyl isocyanide). Simple alkyl halides (R-X) generally do not have common functional group isomers with the same molecular formula; positional isomerism (different position of X on the carbon chain) is possible, but not a different functional group itself that is isomeric to an alkyl halide.

Isomers share the same molecular formula but differ in the arrangement of atoms. Different types of isomerism include structural isomerism (chain, positional, functional group, metamerism, tautomerism) and stereoisomerism (geometric and optical). Functional group isomerism is a type of structural isomerism.

15. Which one of the following elements cannot be detected by “Lassaigne’s

Which one of the following elements cannot be detected by “Lassaigne’s test”?

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Lassaigne’s test (Sodium Fusion Test) is used to detect the presence of elements like nitrogen, sulfur, and halogens (chlorine, bromine, iodine) in an organic compound. The organic substance is fused with metallic sodium, converting these elements into ionic compounds (e.g., NaCN, Na2S, NaCl, NaBr, NaI) which are then extracted with water and tested for using specific reagents. Fluorine (F) is a halogen, but Lassaigne’s test is generally not used or is unreliable for its detection because sodium fluoride (NaF) is less soluble than other sodium halides, and organic fluoro compounds may not completely decompose to ionic fluoride upon fusion. Therefore, fluorine cannot be reliably detected by Lassaigne’s test.

– Lassaigne’s test detects N, S, Cl, Br, and I in organic compounds.
– Fluorine (F) is typically not detectable by Lassaigne’s test due to difficulties in forming and dissolving ionic fluoride.

For detecting fluorine in organic compounds, alternative methods like combustion followed by fluoride ion-selective electrode measurement or gravimetric analysis as calcium fluoride are used.

16. Very small insoluble particles in a liquid may be separated from it by

Very small insoluble particles in a liquid may be separated from it by using

crystallization

fractional distillation

centrifugation

decantation

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To separate very small insoluble particles from a liquid, techniques that enhance sedimentation or filtration are required. Centrifugation (C) is a process that uses centrifugal force to accelerate the sedimentation of particles suspended in a liquid. This is particularly effective for separating very fine or colloidal particles that would settle very slowly or not at all under gravity alone. Crystallization (A) is for dissolved substances. Fractional distillation (B) is for separating miscible liquids with different boiling points. Decantation (D) involves carefully pouring off the liquid after the solid has settled, which is less effective for very small particles that remain suspended.

– Centrifugation uses centrifugal force to separate solids from liquids based on density.
– It is effective for separating very small or finely suspended insoluble particles.

Centrifugation is widely used in laboratories, industry, and medical settings (e.g., separating blood components). Other methods for separating very fine insoluble particles include filtration, but centrifugation is often faster for small particles in suspension.

17. The ‘Gujral Doctrine’ relates to which one of the following issues?

The ‘Gujral Doctrine’ relates to which one of the following issues?

Build trust between India and its neighbours

Initiate dialogue with all insurgent groups in India

Undertake development activities in Naxal-dominated areas

Ensure food security

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The ‘Gujral Doctrine’ is a set of five principles formulated by India’s then-External Affairs Minister (later Prime Minister) I. K. Gujral in 1996. The doctrine aimed to improve India’s relationship with its neighbours by offering unilateral concessions where possible, without demanding strict reciprocity, thereby building trust and confidence. The core idea was that India, being the larger country, should be generous in dealing with its smaller neighbours in South Asia to create a stable and friendly regional environment. Option A, “Build trust between India and its neighbours,” accurately reflects the central theme and purpose of the doctrine.

– The Gujral Doctrine is a foreign policy approach initiated by I. K. Gujral.
– Its main aim was to improve relations with India’s immediate neighbours, primarily by offering unilateral concessions to build trust.

The five principles of the Gujral Doctrine are: 1) Non-reciprocity with neighbours like Bangladesh, Bhutan, Maldives, Nepal, and Sri Lanka; 2) No South Asian country should allow its territory to be used against the interest of another country of the region; 3) Non-interference in internal affairs; 4) Respect for territorial integrity and sovereignty; 5) Settlement of all disputes through peaceful bilateral negotiations.

18. The ‘Beijing Declaration’ is concerned with which one of the following

The ‘Beijing Declaration’ is concerned with which one of the following issues?

Rights of children

Rights of women

Right to development

Reduction of tariffs

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The Beijing Declaration and Platform for Action was adopted at the Fourth World Conference on Women, held in Beijing, China, in 1995. It is considered a key global policy document on gender equality and women’s empowerment. The declaration affirmed the commitment of governments to the equal rights and inherent human dignity of women and girls and outlined twelve critical areas of concern requiring action to advance women’s rights.

– The Beijing Declaration was adopted at the Fourth World Conference on Women in 1995.
– It is a foundational document for advancing gender equality and women’s rights globally.

The twelve critical areas of concern identified in the Platform for Action include poverty, education, health, violence against women, armed conflict, the economy, power and decision-making, institutional mechanisms, human rights, media, environment, and the girl child.

19. The ‘Kyoto Protocol’ is an international treaty that commits State par

The ‘Kyoto Protocol’ is an international treaty that commits State parties to reduction in

poverty

greenhouse gases emission

nuclear armaments

agricultural subsidy

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The Kyoto Protocol was an international treaty negotiated under the framework of the United Nations Framework Convention on Climate Change (UNFCCC). Its main objective was to commit industrialized countries and economies in transition to limit and reduce greenhouse gas (GHG) emissions in accordance with agreed individual targets. It is directly concerned with combating climate change by reducing the emissions of key greenhouse gases like carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.

– The Kyoto Protocol is an international treaty under the UNFCCC.
– It sets binding emission reduction targets for developed countries for greenhouse gases.

The Kyoto Protocol was adopted in Kyoto, Japan, on 11 December 1997 and entered into force on 16 February 2005. It was followed by the Doha Amendment (for a second commitment period) and later superseded by the Paris Agreement.

20. The South China Sea Dispute involves which of the following countries?

The South China Sea Dispute involves which of the following countries?

1. China
2. Vietnam
3. Malaysia
4. Indonesia

Select the correct answer using the code given below.

1 and 4

1 and 2 only

1, 2 and 3

2, 3 and 4

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The South China Sea dispute involves complex territorial and maritime claims among several countries bordering the sea. The primary claimants to islands (such as the Spratly Islands and Paracel Islands) and maritime zones include China (mainland), Taiwan, Vietnam, the Philippines, Malaysia, and Brunei. Indonesia is involved in disputes with China over fishing rights in its Exclusive Economic Zone (EEZ) that overlaps with China’s expansive nine-dash line claim, although Indonesia is not typically listed as a claimant to the islands themselves. Among the options provided, the set including China (1), Vietnam (2), and Malaysia (3) represents some of the key countries directly involved in the territorial dispute over islands and maritime claims.

– Key claimants in the South China Sea territorial disputes include China, Vietnam, Philippines, Malaysia, Brunei, and Taiwan.
– Indonesia is involved in maritime disputes with China regarding its EEZ.

The dispute centers on sovereignty over islands and rocks, historical rights, and rights to resources within the sea, leading to significant geopolitical tensions. The Nine-Dash Line used by China to assert its claims is a major point of contention.