UPSC CDS-2 Archives

41. A particle moves with uniform acceleration along a straight line from

A particle moves with uniform acceleration along a straight line from rest. The percentage increase in displacement during sixth second compared to that in fifth second is about

11%

22%

33%

44%

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

For a particle starting from rest (initial velocity u = 0) and moving with uniform acceleration ‘a’, the displacement in the n-th second (S_n) is given by the formula S_n = u + a(n – 1/2). Since u = 0, S_n = a(n – 1/2).
Displacement in the fifth second (n=5): S₅ = a(5 – 1/2) = a(4.5).
Displacement in the sixth second (n=6): S₆ = a(6 – 1/2) = a(5.5).
The percentage increase in displacement during the sixth second compared to the fifth second is calculated as [(S₆ – S₅) / S₅] * 100%.
Percentage Increase = [(a(5.5) – a(4.5)) / a(4.5)] * 100% = [a(5.5 – 4.5) / a(4.5)] * 100% = [a(1) / a(4.5)] * 100% = (1 / 4.5) * 100% = (10 / 45) * 100% = (2 / 9) * 100% ≈ 0.2222 * 100% ≈ 22.22%.
The closest option is 22%.

– Displacement in the n-th second formula: S_n = u + a(n – 1/2).
– Uniform acceleration from rest means u=0.
– Percentage increase calculation involves finding the difference, dividing by the original value, and multiplying by 100.

The total displacement after ‘n’ seconds is given by S = ut + (1/2)at². For a body starting from rest (u=0), S = (1/2)at². The displacement in the n-th second is the difference between the total displacement after n seconds and the total displacement after (n-1) seconds: S_n = S(n) – S(n-1) = (1/2)an² – (1/2)a(n-1)² = (1/2)a [n² – (n² – 2n + 1)] = (1/2)a [n² – n² + 2n – 1] = (1/2)a (2n – 1) = a(n – 1/2). This confirms the formula used.

Join Our Telegram Channel

42. Which of the following is the general formula for saturated

Which of the following is the general formula for saturated hydrocarbons?

CnH₂n+2

CnH₂n-2

CnH₂n+1

CnH₂n-1

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

Saturated hydrocarbons, also known as alkanes, are hydrocarbons where all carbon-carbon bonds are single bonds. The general formula for alkanes is CnH₂n+2, where ‘n’ represents the number of carbon atoms. This formula represents the maximum number of hydrogen atoms that can be bonded to ‘n’ carbon atoms in an acyclic structure with only single bonds.

– Saturated hydrocarbons are alkanes.
– They contain only single bonds between carbon atoms.
– The general formula represents the relationship between the number of carbon and hydrogen atoms in such molecules.

Unsaturated hydrocarbons include alkenes (at least one double bond, general formula CnH₂n) and alkynes (at least one triple bond, general formula CnH₂n-2). Cycloalkanes (cyclic saturated hydrocarbons) have the general formula CnH₂n.

Join Our Telegram Channel

43. The compound C₇H₇NO₂ has

The compound C₇H₇NO₂ has

17 atoms in a molecule of the compound

equal molecules of C and H by mass

twice the mass of oxygen atoms compared to nitrogen atoms

twice the mass of nitrogen atoms compared to hydrogen atoms

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

The compound C₇H₇NO₂ has twice the mass of nitrogen atoms compared to hydrogen atoms.

Using approximate atomic masses (C=12, H=1, N=14, O=16), we can calculate the total mass of each element in one molecule: Mass of C = 7 * 12 = 84; Mass of H = 7 * 1 = 7; Mass of N = 1 * 14 = 14; Mass of O = 2 * 16 = 32.

Let’s evaluate each option:
A) Total atoms = 7 (C) + 7 (H) + 1 (N) + 2 (O) = 17 atoms. This statement is true.
B) Mass of C (84) is not equal to mass of H (7). This statement is false.
C) Mass of O atoms (32) is not twice the mass of N atoms (14) (2 * 14 = 28). This statement is false.
D) Mass of N atom (14) is twice the mass of H atoms (7) (2 * 7 = 14). This statement is true.
Although option A is also a true statement about the compound, option D is typically considered the intended answer in such chemistry questions focusing on mass relationships derived from the formula, particularly when sourced from test banks that confirm D.

Join Our Telegram Channel

44. Which of the following characteristics is common to hydrogen, nitrogen

Which of the following characteristics is common to hydrogen, nitrogen, oxygen and carbon dioxide?

Join Our Telegram Channel

They are all diatomic.

They are all gases at room temperature.

They are all coloured.

They all have same reactivity.

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

Hydrogen, nitrogen, oxygen, and carbon dioxide are all gases at room temperature.

At standard room temperature (around 20-25 °C) and pressure (1 atm), Hydrogen (H₂), Nitrogen (N₂), Oxygen (O₂), and Carbon Dioxide (CO₂) all exist in the gaseous state.

Option A is incorrect because while H₂, N₂, and O₂ are diatomic, CO₂ is triatomic. Option C is incorrect because all four gases are colourless. Option D is incorrect because they have vastly different reactivities (e.g., flammability, ability to support combustion, inertness).

45. Reaction between which of the following two reactants will produce hyd

Reaction between which of the following two reactants will produce hydrogen gas?

Join Our Telegram Channel

Magnesium and hydrochloric acid

Copper and dilute nitric acid

Calcium carbonate and hydrochloric acid

Zinc and nitric acid

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

The reaction between Magnesium and hydrochloric acid will produce hydrogen gas.

Reactive metals, generally those above hydrogen in the reactivity series (like Magnesium, Zinc, etc.), react with dilute acids to displace hydrogen and produce hydrogen gas and a salt.

The reaction in option A is: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g).
Option B (Copper and dilute nitric acid): Nitric acid is an oxidizing acid, and while it reacts with copper, it typically produces nitrogen oxides rather than hydrogen gas.
Option C (Calcium carbonate and hydrochloric acid): This produces carbon dioxide gas (CO₂), water, and calcium chloride (CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂).
Option D (Zinc and nitric acid): Similar to copper, zinc reacts with nitric acid to produce zinc nitrate and nitrogen oxides (or ammonium nitrate with very dilute acid), not primarily hydrogen gas.

46. How many moles of CO can be obtained by reacting 2·0 mole of CH₄ with

How many moles of CO can be obtained by reacting 2·0 mole of CH₄ with 2·0 mole of O₂ according to the equation given below?
CH₄(g) + 1/2 O₂ → CO + 2H₂

Join Our Telegram Channel

2·0

0·5

2·5

4·0

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

2.0 moles of CO can be obtained by reacting 2.0 mole of CH₄ with 2.0 mole of O₂.

The balanced chemical equation is CH₄(g) + 1/2 O₂ → CO + 2H₂. We need to determine the limiting reactant based on the initial amounts (2.0 mol CH₄ and 2.0 mol O₂).

According to the stoichiometry, 1 mole of CH₄ reacts with 0.5 moles of O₂.
For 2.0 moles of CH₄, 2.0 * 0.5 = 1.0 mole of O₂ is required. We have 2.0 moles of O₂, which is more than required. Thus, CH₄ is the limiting reactant.
The amount of product is determined by the limiting reactant. From the equation, 1 mole of CH₄ produces 1 mole of CO. Therefore, 2.0 moles of CH₄ will produce 2.0 moles of CO.

47. Two reactants in a flask at room temperature are producing bubbles of

Two reactants in a flask at room temperature are producing bubbles of a gas that turn limewater milky. The reactants could be

zinc and hydrochloric acid

magnesium carbonate and hydrochloric acid

methane and oxygen

copper and dilute hydrochloric acid

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2018

Download PDF Attempt Online

The reaction between magnesium carbonate and hydrochloric acid produces carbon dioxide gas, which turns limewater milky.

Carbonates and bicarbonates react with acids to produce carbon dioxide gas (CO₂), water, and a salt. CO₂ gas, when bubbled through limewater (calcium hydroxide solution), reacts to form insoluble calcium carbonate, which appears as a milky precipitate.

The reaction in option B is: MgCO₃(s) + 2HCl(aq) → MgCl₂(aq) + H₂O(l) + CO₂(g).
Option A produces hydrogen gas (Zn + 2HCl → ZnCl₂ + H₂), which does not turn limewater milky.
Option C (methane and oxygen) is combustion, which doesn’t occur simply by mixing at room temperature and requires ignition.
Option D (copper and dilute hydrochloric acid) does not react as copper is less reactive than hydrogen.

Join Our Telegram Channel

48. Which one of the following is not included in the National Air Quality

Which one of the following is not included in the National Air Quality Index?

Sulphur

Nitrogen dioxide

Lead

Methane

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2017

Download PDF Attempt Online

Methane is not included in the pollutants measured for the National Air Quality Index (NAQI) in India.

The National Air Quality Index (NAQI) in India measures the levels of eight major air pollutants: Particulate Matter (PM₁₀ and PM₂.₅), Ozone (O₃), Sulphur Dioxide (SO₂), Nitrogen Dioxide (NO₂), Carbon Monoxide (CO), Ammonia (NH₃), and Lead (Pb).

Methane (CH₄) is a significant greenhouse gas contributing to climate change, but it is not one of the standard criteria pollutants monitored for reporting ambient air quality health impacts via the NAQI. Sulphur, Nitrogen dioxide, and Lead are represented by SO₂, NO₂, and Pb respectively, which are part of the NAQI pollutants.

Join Our Telegram Channel

49. Which one of the following is not a feature of the Saansad Adarsh Gram

Which one of the following is not a feature of the Saansad Adarsh Gram Yojana (SAGY)?

Join Our Telegram Channel

It focuses on community participation.

It is to be guided by a Member of the Parliament.

It aims at creating infrastructure for the village.

A Village Development Plan would be prepared for every identified Gram Panchayat.

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CDS-2 – 2017

Download PDF Attempt Online

While infrastructure creation is a component, the statement “It aims at creating infrastructure for the village” is not the defining or sole feature of the Saansad Adarsh Gram Yojana (SAGY). SAGY’s aim is holistic development.

Saansad Adarsh Gram Yojana (SAGY) is a village development project launched by the Government of India. It aims for the holistic development of selected villages, covering various aspects including social development, human development, economic development, environmental sanitation, village cleanliness, infrastructure, livelihood, and governance.

Key features of SAGY include: (A) Focus on community participation as a core principle; (B) The scheme is guided and mentored by a Member of Parliament (MP) who adopts a Gram Panchayat; (D) A Village Development Plan (VDP) is prepared for each identified Gram Panchayat, outlining activities for integrated development. Option C is part of the development but not the comprehensive aim.