Chemistry MCQs – Set 1: Advanced Questions for UPSC/PCS Exam Prep

  1. The atomic number of an element represents –
    (A) Number of neutrons
    (B) Number of protons
    (C) Mass number
    (D) Number of isotopes
    Answer: (B)
  2. The most electronegative element is –
    (A) Fluorine
    (B) Oxygen
    (C) Chlorine
    (D) Nitrogen
    Answer: (A)
  3. Avogadro’s number is –
    (A) 6.022 × 10²²
    (B) 6.022 × 10²³
    (C) 3.011 × 10²³
    (D) 1.66 × 10⁻²³
    Answer: (B)
  4. The valency of nitrogen in NH₃ is –
    (A) 1
    (B) 3
    (C) 5
    (D) 0
    Answer: (B)
  5. pH of neutral solution at 25°C is –
    (A) 0
    (B) 1
    (C) 7
    (D) 14
    Answer: (C)
  6. A covalent bond is formed by –
    (A) Transfer of electrons
    (B) Sharing of electrons
    (C) Gain of electrons
    (D) Loss of protons
    Answer: (B)
  7. The gas evolved during fermentation is –
    (A) O₂
    (B) N₂
    (C) CO₂
    (D) H₂
    Answer: (C)
  8. Which one is an acidic salt?
    (A) NaCl
    (B) Na₂CO₃
    (C) NaHSO₄
    (D) KNO₃
    Answer: (C)
  9. The oxidation number of oxygen in H₂O₂ is –
    (A) –1
    (B) –2
    (C) 0
    (D) +1
    Answer: (A)
  10. The chemical formula of baking soda is –
    (A) Na₂CO₃
    (B) NaHCO₃
    (C) CaCO₃
    (D) NaCl
    Answer: (B)
  11. Atomic radius across a period –
    (A) Increases
    (B) Decreases
    (C) Remains same
    (D) First increases then decreases
    Answer: (B)
  12. Which is a noble gas?
    (A) Hydrogen
    (B) Nitrogen
    (C) Argon
    (D) Oxygen
    Answer: (C)
  13. The first element in the periodic table is –
    (A) Helium
    (B) Lithium
    (C) Hydrogen
    (D) Oxygen
    Answer: (C)
  14. A solution with pH = 2 is –
    (A) Neutral
    (B) Weak acid
    (C) Strong acid
    (D) Strong base
    Answer: (C)
  15. The SI unit of molar mass is –
    (A) g
    (B) g/mol
    (C) kg/mol
    (D) mol/kg
    Answer: (B)
  16. The most reactive metal is –
    (A) Copper
    (B) Gold
    (C) Sodium
    (D) Silver
    Answer: (C)
  17. The element with highest melting point is –
    (A) Tungsten
    (B) Iron
    (C) Gold
    (D) Carbon
    Answer: (A)
  18. Which acid is present in vinegar?
    (A) Citric acid
    (B) Acetic acid
    (C) Oxalic acid
    (D) Tartaric acid
    Answer: (B)
  19. Hard water contains –
    (A) NaCl
    (B) KNO₃
    (C) Ca²⁺ and Mg²⁺
    (D) SO₂
    Answer: (C)
  20. The alkaline earth metals are in group –
    (A) 1
    (B) 2
    (C) 13
    (D) 17
    Answer: (B)
  21. Electrolysis of water gives –
    (A) H₂ and O₂
    (B) H₂ only
    (C) O₂ only
    (D) H₂ and CO₂
    Answer: (A)
  22. Rutherford’s model failed because it –
    (A) Could not explain stability
    (B) Could not explain spectra
    (C) Did not include electrons
    (D) Assumed wrong atomic mass
    Answer: (A)
  23. A mixture of salt and sand can be separated by –
    (A) Filtration
    (B) Sublimation
    (C) Chromatography
    (D) Crystallization
    Answer: (A)
  24. Organic chemistry is the study of –
    (A) Metals
    (B) Gases
    (C) Carbon compounds
    (D) Acids
    Answer: (C)
  25. The most abundant element in Earth’s crust is –
    (A) Silicon
    (B) Oxygen
    (C) Aluminum
    (D) Iron
    Answer: (B)
  26. Ammonia is basic because it –
    (A) Has hydrogen
    (B) Has lone pair of electrons
    (C) Is colorless
    (D) Dissolves in water
    Answer: (B)
  27. Bleaching powder is –
    (A) CaCO₃
    (B) Ca(OH)₂
    (C) CaOCl₂
    (D) CaCl₂
    Answer: (C)
  28. Transition elements are found in –
    (A) s-block
    (B) p-block
    (C) d-block
    (D) f-block
    Answer: (C)
  29. A strong electrolyte –
    (A) Partially dissociates
    (B) Does not conduct
    (C) Completely dissociates
    (D) Has covalent bond
    Answer: (C)
  30. Which is a greenhouse gas?
    (A) CO₂
    (B) N₂
    (C) He
    (D) H₂
    Answer: (A)
  31. The noble gas configuration of neon is –
    (A) 1s²2s²2p⁶
    (B) 1s²2s²2p⁵
    (C) 2s²2p⁶3s¹
    (D) 1s²2s²2p⁴
    Answer: (A)
  32. Hydrogen peroxide acts as –
    (A) Only oxidizing agent
    (B) Only reducing agent
    (C) Both
    (D) Neutral
    Answer: (C)
  33. Inert gases are chemically –
    (A) Active
    (B) Inert
    (C) Reactive
    (D) Explosive
    Answer: (B)
  34. The metal stored in kerosene is –
    (A) Zinc
    (B) Sodium
    (C) Magnesium
    (D) Iron
    Answer: (B)
  35. The first man-made element is –
    (A) Technetium
    (B) Plutonium
    (C) Californium
    (D) Uranium
    Answer: (A)
  36. The main constituent of glass is –
    (A) CaCO₃
    (B) SiO₂
    (C) NaCl
    (D) Fe₂O₃
    Answer: (B)
  37. The chemical name of rust is –
    (A) Fe₂O₃·xH₂O
    (B) Fe₃O₄
    (C) FeO
    (D) FeCl₃
    Answer: (A)
  38. The most malleable metal is –
    (A) Iron
    (B) Copper
    (C) Gold
    (D) Zinc
    Answer: (C)
  39. Radioactive isotope of hydrogen is –
    (A) Protium
    (B) Deuterium
    (C) Tritium
    (D) Isobutane
    Answer: (C)
  40. Which oxide is acidic?
    (A) CO₂
    (B) CaO
    (C) MgO
    (D) Na₂O
    Answer: (A)
  41. Which polymer is used in non-stick cookware?
    (A) PVC
    (B) Nylon
    (C) Teflon
    (D) Bakelite
    Answer: (C)
  42. Red litmus turns blue in –
    (A) Acid
    (B) Base
    (C) Salt
    (D) Neutral
    Answer: (B)
  43. Which bond is the strongest?
    (A) Ionic
    (B) Covalent
    (C) Metallic
    (D) Hydrogen
    Answer: (B)
  44. Which gas is used in fire extinguishers?
    (A) CO₂
    (B) O₂
    (C) H₂
    (D) N₂
    Answer: (A)
  45. The atomic mass unit (amu) is based on –
    (A) H
    (B) O
    (C) C-12
    (D) U
    Answer: (C)
  46. Which metal reacts with cold water?
    (A) Copper
    (B) Zinc
    (C) Sodium
    (D) Silver
    Answer: (C)
  47. Which one is a non-metal?
    (A) Bismuth
    (B) Gallium
    (C) Phosphorus
    (D) Lead
    Answer: (C)
  48. The number of moles in 22.4 L of a gas at STP is –
    (A) 1
    (B) 0.5
    (C) 2
    (D) 1.5
    Answer: (A)
  49. Isotopes have the same –
    (A) Atomic number
    (B) Mass number
    (C) Neutrons
    (D) Electrons and neutrons
    Answer: (A)
  50. The modern periodic law is based on –
    (A) Atomic mass
    (B) Atomic number
    (C) Density
    (D) Volume
    Answer: (B)
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