NEET Chemistry 4 — Questions and Answers
Question 1: Which of the following compounds shows geometrical isomerism?
- 2-butyne
- Propene
- 2-butene (Correct answer)
- Isobutene
Correct answer: 2-butene
2-Butene (CH₃–CH=CH–CH₃) shows cis-trans geometrical isomerism because each double-bond carbon has two different substituents.
Question 2: In the Born-Haber cycle for NaCl formation, which step is endothermic?
- Ionization of Na
- Electron gain by Cl
- Lattice formation
- Sublimation of Na (Correct answer)
Correct answer: Sublimation of Na
Sublimation of solid sodium to gaseous atoms is endothermic as energy must be supplied to overcome metallic bonding.
Question 3: The half-life of a first-order reaction is 693 seconds. The rate constant is approximately:
- 0.001 s⁻¹ (Correct answer)
- 0.693 s⁻¹
- 1.0 s⁻¹
- 6.93 × 10⁻⁴ s⁻¹
Correct answer: 0.001 s⁻¹
For a first-order reaction, k = 0.693/t½ = 0.693/693 = 0.001 s⁻¹.
Question 4: Which of the following is NOT a transition element?
- Zinc (Zn) (Correct answer)
- Iron (Fe)
- Copper (Cu)
- Nickel (Ni)
Correct answer: Zinc (Zn)
Zinc (Zn, [Ar]3d¹⁰4s²) is not a transition element because its d-orbitals are completely filled in both the element and its common ion (Zn²⁺).
Question 5: Which of the following is the correct order of boiling points of noble gases?
- He < Ne < Ar < Kr < Xe (Correct answer)
- Xe < Kr < Ar < Ne < He
- He < Ar < Ne < Kr < Xe
- Ne < He < Ar < Kr < Xe
Correct answer: He < Ne < Ar < Kr < Xe
Boiling points of noble gases increase with atomic mass due to increasing London dispersion forces: He < Ne < Ar < Kr < Xe.
Question 6: The product formed when aniline reacts with NaNO₂ and HCl at 0–5°C is:
- Chlorobenzene
- Nitrobenzene
- Benzene diazonium chloride (Correct answer)
- Phenol
Correct answer: Benzene diazonium chloride
Aniline undergoes diazotization with NaNO₂/HCl at 0–5°C to form benzene diazonium chloride (C₆H₅N₂⁺Cl⁻).
Question 7: Which of the following colligative properties is used to determine the molecular weight of macromolecules?
- Elevation in boiling point
- Depression in freezing point
- Osmotic pressure (Correct answer)
- Relative lowering of vapour pressure
Correct answer: Osmotic pressure
Osmotic pressure is preferred for macromolecules because even dilute solutions give measurable osmotic pressure, unlike the small changes in other colligative properties.
NEET Chemistry 4
Which of the following compounds shows geometrical isomerism?