1. Which quantum number determines the orientation of an orbital in space?

  • A. Principal quantum number (n)
  • B. Azimuthal quantum number (l)
  • C. Magnetic quantum number (ml)
  • D. Spin quantum number (ms)

Answer: C. Magnetic quantum number (ml)

Explanation: The magnetic quantum number (ml) specifies the orientation of an orbital in space and ranges from –l to +l.

2. Which of the following species is isoelectronic with Ne?

  • A. Na+
  • B. Mg2+
  • C. F−
  • D. All of the above

Answer: D. All of the above

Explanation: Na⁺, Mg²⁺ and F⁻ each contain 10 electrons, the same as neon.

3. Which gas deviates the most from ideal behaviour under high pressure and low temperature?

  • A. Hydrogen
  • B. Helium
  • C. Ammonia
  • D. Neon

Answer: C. Ammonia

Explanation: Ammonia exhibits strong intermolecular hydrogen bonding, causing significant deviation from ideal gas behaviour.

4. According to VSEPR theory, the shape of NH3 is:

  • A. Trigonal planar
  • B. Tetrahedral
  • C. Trigonal pyramidal
  • D. Bent

Answer: C. Trigonal pyramidal

Explanation: NH₃ has four electron pairs (3 bond pairs + 1 lone pair), giving a trigonal pyramidal molecular geometry.

5. Which of the following has the highest first ionization enthalpy?

  • A. Lithium
  • B. Boron
  • C. Beryllium
  • D. Carbon

Answer: D. Carbon

Explanation: Across Period 2, first ionization enthalpy generally increases from left to right, with carbon having the highest among the given elements.

6. Which reagent is used to distinguish between aldehydes and ketones?

  • A. Bromine water
  • B. Tollens' reagent
  • C. Sodium hydroxide
  • D. Dilute hydrochloric acid

Answer: B. Tollens' reagent

Explanation: Aldehydes reduce Tollens' reagent to produce a silver mirror, whereas ketones generally do not.

7. Which of the following is an example of a strong electrolyte?

  • A. Acetic acid
  • B. Glucose
  • C. Sodium chloride solution
  • D. Urea

Answer: C. Sodium chloride solution

Explanation: Sodium chloride dissociates completely into Na⁺ and Cl⁻ ions in aqueous solution, making it a strong electrolyte.

8. The oxidation state of chromium in K2Cr2O7 is:

  • A. +3
  • B. +4
  • C. +6
  • D. +7

Answer: C. +6

Explanation: In K₂Cr₂O₇, the oxidation state of each chromium atom is +6.

9. Which hybridization is present in ethyne (C2H2)?

  • A. sp3
  • B. sp2
  • C. sp
  • D. dsp2

Answer: C. sp

Explanation: Each carbon atom in ethyne is sp hybridized, forming one σ bond and two π bonds in the C≡C triple bond.

10. Which of the following compounds exhibits hydrogen bonding between its molecules?

  • A. CH4
  • B. HCl
  • C. NH3
  • D. CO2

Answer: C. NH3

Explanation: NH₃ contains N–H bonds and a lone pair on nitrogen, allowing intermolecular hydrogen bonding.