UPSC NDA-1

41. Which of the following statements regarding earthquakes is/are correct

Which of the following statements regarding earthquakes is/are correct ?

  • 1. The point on the Earth’s surface directly above the focus is called the epicentre of the earthquake.
  • 2. Earthquakes generate Primary and Secondary waves that radiate outward from the earthquake focus.
  • 3. Deep-focus earthquakes are likely to cause more damage than shallow-focus earthquakes.

Select the answer using the code given below :

[amp_mcq option1=”1 only” option2=”1 and 2 only” option3=”2 and 3 only” option4=”1, 2 and 3″ correct=”option2″]

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Statements 1 and 2 are correct, while statement 3 is incorrect.
Statement 1 accurately defines the epicentre as the point on the Earth’s surface directly above the focus (hypocentre), which is the point where the earthquake originates within the Earth. Statement 2 is correct as earthquakes generate various types of seismic waves, including Primary (P) waves and Secondary (S) waves (body waves), which propagate outwards from the focus. Statement 3 is incorrect; deep-focus earthquakes generally cause less damage at the surface than shallow-focus earthquakes of similar magnitude because the seismic waves travel a greater distance and lose energy before reaching the surface.
Earthquake magnitude measures the energy released at the source, while intensity measures the shaking and damage caused at a specific location. Surface waves typically cause the most damage.

42. Which of the following statements regarding neap tides is/are correct

Which of the following statements regarding neap tides is/are correct ?

  • 1. It occurs every 14 – 15 days, which coincides with the first and third quarter of the Moon.
  • 2. This tide has a small tidal range because the gravitational forces of the Moon and the Sun are in quadrature.

Select the answer using the code given below :

[amp_mcq option1=”1 only” option2=”2 only” option3=”Both 1 and 2″ option4=”Neither 1 nor 2″ correct=”option3″]

This question was previously asked in
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Statements 1 and 2 are correct.
Neap tides occur twice a lunar month, during the first and third quarter Moon. At these times, the gravitational pull of the Sun is at a right angle to the gravitational pull of the Moon relative to Earth. This alignment causes the gravitational forces to partially cancel each other out, resulting in smaller differences between high and low tides, which is known as a smaller tidal range. This phenomenon occurs approximately every 14-15 days, halfway between spring tides.
Spring tides, which have the largest tidal range, occur during the new Moon and full Moon when the Sun, Earth, and Moon are aligned. Tidal range is the difference in height between high tide and low tide.

43. Which one among the following oxides has the highest melting point ?

Which one among the following oxides has the highest melting point ?

[amp_mcq option1=”Na₂O” option2=”MgO” option3=”Fe₂O₃” option4=”CuO” correct=”option2″]

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Among the given options, Magnesium oxide (MgO) has the highest melting point.
Oxides of highly electropositive metals (like those in Group 1 and 2) and transition metals are generally ionic compounds with high melting points due to strong electrostatic forces in the crystal lattice. MgO is a Group 2 metal oxide with high lattice energy primarily due to the +2 and -2 charges of Mg²⁺ and O²⁻ ions and their relatively small ionic radii, resulting in a very high melting point (~2852 °C).
Comparing the options: Na₂O (~1132 °C), MgO (~2852 °C), Fe₂O₃ (~1565 °C, decomposes), CuO (~1326 °C, decomposes). MgO’s melting point is significantly higher than the others listed, making it a refractory material.

44. Which among the following is the correct composition of Borax ?

Which among the following is the correct composition of Borax ?

[amp_mcq option1=”Sodium, Boron, Magnesium and Hydrogen” option2=”Sodium, Boron, Oxygen and Hydrogen” option3=”Potassium, Boron, Oxygen and Hydrogen” option4=”Sodium, Boron, Nitrogen and Hydrogen” correct=”option2″]

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The correct composition of Borax includes Sodium, Boron, Oxygen, and Hydrogen.
Borax is commonly found as the mineral sodium tetraborate decahydrate, with the chemical formula Na₂B₄O₇·10H₂O. This formula clearly shows the presence of Sodium (Na), Boron (B), Oxygen (O), and Hydrogen (H).
The B₄O₇²⁻ anion in borax is actually a complex polyborate ion, often more accurately represented as [B₄O₅(OH)₄]²⁻ in its hydrated forms. The decahydrate contains 10 water molecules of crystallization.

45. Soap with water forms :

Soap with water forms :

[amp_mcq option1=”Metallotropic liquid crystal” option2=”Thermotropic liquid crystal” option3=”Homogeneous solution” option4=”Lyotropic liquid crystal” correct=”option4″]

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Soap with water can form lyotropic liquid crystals, especially at higher concentrations.
Soap molecules are amphiphilic, having a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail. In water, they aggregate into structures like micelles, bilayers, or vesicles depending on concentration and temperature. These ordered structures often exhibit liquid crystalline phases, which are classified as lyotropic because their formation depends on the concentration of the solute (soap) in the solvent (water).
A homogeneous solution is formed at very low soap concentrations where molecules are dispersed individually. However, the characteristic behavior of soap forming micelles and other structured phases at higher concentrations leads to lyotropic liquid crystal phases. Thermotropic liquid crystals are formed by pure substances or mixtures that show liquid crystalline phases at different temperatures without a solvent. Metallotropic liquid crystals are formed from molten salts.

46. Which one among the following is known as Milk of Magnesia ?

Which one among the following is known as Milk of Magnesia ?

[amp_mcq option1=”Magnesium bicarbonate” option2=”Magnesium carbonate” option3=”Magnesium sulphate” option4=”Magnesium hydroxide” correct=”option4″]

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Milk of Magnesia is the common name for an aqueous suspension of magnesium hydroxide.
Magnesium hydroxide (Mg(OH)₂) is a slightly soluble base. When suspended in water, it forms a milky white liquid known as Milk of Magnesia. It is commonly used as an antacid to neutralize stomach acid and as a laxative.
Magnesium carbonate is also used as an antacid but is not called Milk of Magnesia. Magnesium sulphate (Epsom salt) is used as a laxative and for baths. Magnesium bicarbonate exists only in aqueous solution.

47. Which one among the following is present in the nettle leaf hairs that

Which one among the following is present in the nettle leaf hairs that causes burning pain ?

[amp_mcq option1=”Methanoic acid” option2=”Ethanoic acid” option3=”Benzoic acid” option4=”Acetic acid” correct=”option1″]

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UPSC NDA-1 – 2024
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Methanoic acid is present in nettle leaf hairs and causes a burning pain.
The stinging hairs (trichomes) of nettle plants contain several irritants, including histamine, acetylcholine, serotonin, and an acid. The primary acid responsible for the burning and stinging sensation is formic acid, also known by its IUPAC name, methanoic acid (HCOOH).
Ethanoic acid is acetic acid (CH₃COOH), found in vinegar. Benzoic acid (C₆H₅COOH) is an aromatic carboxylic acid. While other chemicals contribute, methanoic acid is the key acidic component causing the initial sting.

48. What is the coordination number of Na⁺ and Cl⁻ ions in NaCl lattice ?

What is the coordination number of Na⁺ and Cl⁻ ions in NaCl lattice ?

[amp_mcq option1=”6, 1″ option2=”1, 6″ option3=”6, 6″ option4=”5, 5″ correct=”option3″]

This question was previously asked in
UPSC NDA-1 – 2024
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In the NaCl crystal lattice, both Na⁺ and Cl⁻ ions have a coordination number of 6.
The NaCl crystal structure is a face-centered cubic (FCC) arrangement where each Na⁺ ion is octahedrally surrounded by six Cl⁻ ions, and similarly, each Cl⁻ ion is octahedrally surrounded by six Na⁺ ions.
The coordination number in an ionic lattice refers to the number of oppositely charged ions immediately surrounding a given ion. This coordination number is determined by the relative sizes of the ions and the need to maximize electrostatic attraction while minimizing repulsion.

49. Which one among the following compounds has a sweet and fruity smell ?

Which one among the following compounds has a sweet and fruity smell ?

[amp_mcq option1=”Ethyl alcohol” option2=”Acetic acid” option3=”Ethyl acetate” option4=”Acetophenone” correct=”option3″]

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Ethyl acetate has a sweet and fruity smell.
Esters are a class of organic compounds formed from an alcohol and a carboxylic acid, and they are commonly known for their pleasant, often fruity or flowery odors. Ethyl acetate is an ester derived from ethanol and acetic acid.
Ethyl alcohol (ethanol) has a characteristic alcoholic smell. Acetic acid is a carboxylic acid with a pungent, vinegar-like smell. Acetophenone is a ketone with a sweet, sometimes described as almond-like or floral, smell.

50. Which one among the following statements with reference to the propert

Which one among the following statements with reference to the properties of water is not correct ?

[amp_mcq option1=”The specific heat of water is abnormally high.” option2=”Latent heat of fusion of water is very low.” option3=”Density of water is higher than ice.” option4=”Pure water is a non-conductor of electricity.” correct=”option2″]

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The statement that the latent heat of fusion of water is very low is not correct.
Water has an unusually high latent heat of fusion (approximately 334 J/g or 80 cal/g) and a very high latent heat of vaporization (approximately 2260 J/g or 540 cal/g). These high values are due to the extensive hydrogen bonding in water.
Other statements are correct: Water’s specific heat is abnormally high (~4.18 J/g°C), which helps moderate temperatures. Liquid water is denser than ice due to the open crystalline structure of ice. Pure water has very low electrical conductivity as it contains very few free ions, making it a poor conductor.
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