UK PG Entrance Exam Chemistry Questions
1. Which of the following is a common catalyst in olefin polymerization?
- A) Zeolite
- B) Ziegler–Natta catalyst
- C) Wilkinson’s catalyst
- D) Grubbs’ catalyst
Answer & Explanation
Correct Answer: B) Ziegler–Natta catalyst
Ziegler–Natta catalysts (TiCl₄ with AlEt₃) are widely used for polymerizing alkenes into polyethylene and polypropylene.
2. The particle-in-a-box model predicts that energy levels are:
- A) Equally spaced
- B) Proportional to n²
- C) Independent of box length
- D) Degenerate
Answer & Explanation
Correct Answer: B) Proportional to n²
For a particle in a 1D box, En = (n²h²)/(8mL²). Energy depends on n² and inversely on L².
3. In NMR spectroscopy, downfield shifts (higher δ values) are caused by:
- A) Shielding of nuclei
- B) Deshielding due to electronegative atoms
- C) Increased magnetic field strength
- D) Isotopic substitution
Answer & Explanation
Correct Answer: B) Deshielding due to electronegative atoms
Electronegative atoms withdraw electron density, reducing shielding and causing nuclei to resonate at higher δ values.
4. The geometry of [Ni(CN)₄]²⁻ is:
- A) Tetrahedral
- B) Square planar
- C) Octahedral
- D) Trigonal bipyramidal
Answer & Explanation
Correct Answer: B) Square planar
CN⁻ is a strong field ligand. It causes pairing of electrons in Ni²⁺ (d⁸), leading to dsp² hybridization and square planar geometry.
5. Which gas is primarily responsible for photochemical smog formation?
- A) CO₂
- B) SO₂
- C) NO₂
- D) CH₄
Answer & Explanation
Correct Answer: C) NO₂
Photochemical smog results from NO₂ and hydrocarbons reacting under sunlight, producing ozone and PANs.
6. Which orbital overlap leads to sigma bond formation?
- A) Sideways overlap of p orbitals
- B) End-to-end overlap of orbitals
- C) Overlap of d orbitals
- D) None
Answer & Explanation
Correct Answer: B) End-to-end overlap of orbitals
Sigma bonds form by head-on overlap of orbitals, while pi bonds form by sideways overlap.
7. Which of the following is NOT a colligative property?
- A) Vapor pressure lowering
- B) Boiling point elevation
- C) Freezing point depression
- D) Heat of vaporization
Answer & Explanation
Correct Answer: D) Heat of vaporization
Colligative properties depend on the number of solute particles, not their nature. Heat of vaporization is not colligative.
8. Which ligand is considered ambidentate?
- A) CN⁻
- B) NH₃
- C) H₂O
- D) CO
Answer & Explanation
Correct Answer: A) CN⁻
CN⁻ can coordinate through carbon or nitrogen, making it ambidentate.
9. Which law relates osmotic pressure to solute concentration?
- A) Raoult’s law
- B) Henry’s law
- C) van’t Hoff law
- D) Boyle’s law
Answer & Explanation
Correct Answer: C) van’t Hoff law
Osmotic pressure (π) = CRT, similar to ideal gas law.
10. Which of the following is a greenhouse gas?
- A) O₂
- B) N₂
- C) CO₂
- D) Ar
Answer & Explanation
Correct Answer: C) CO₂
CO₂ absorbs infrared radiation, contributing to greenhouse effect.
11. Which type of hybridization is present in methane (CH₄)?
- A) sp
- B) sp²
- C) sp³
- D) dsp²
Answer & Explanation
Correct Answer: C) sp³
Carbon in CH₄ undergoes sp³ hybridization, forming tetrahedral geometry.
12. Which of the following is NOT an intensive property?
- A) Density
- B) Temperature
- C) Pressure
- D) Mass
Answer & Explanation
Correct Answer: D) Mass
Mass depends on the amount of matter, making it extensive. Density, temperature, and pressure are intensive.
13. Which of the following is a secondary standard solution?
- A) NaCl
- B) NaOH
- C) K₂Cr₂O₇
- D) HCl
Answer & Explanation
Correct Answer: B) NaOH
NaOH absorbs CO₂ from air, so it cannot be prepared as a primary standard. It is standardized against a primary standard.
14. Which element has the highest electronegativity?
- A) Oxygen
- B) Fluorine
- C) Nitrogen
- D) Chlorine
Answer & Explanation
Correct Answer: B) Fluorine
Fluorine has the highest electronegativity (3.98 on Pauling scale).
15. Which of the following is a non-polar molecule?
- A) H₂O
- B) CO₂
- C) NH₃
- D) SO₂
Answer & Explanation
Correct Answer: B) CO₂
CO₂ has polar bonds but linear geometry cancels dipole moments, making it non-polar.
16. Which of the following is a strong acid?
- A) H₂CO₃
- B) HCl
- C) CH₃COOH
- D) HF
Answer & Explanation
Correct Answer: B) HCl
HCl dissociates completely in aqueous solution, making it a strong acid. HF and CH₃COOH are weak acids, while H₂CO₃ is a weak diprotic acid.
17. Which of the following complexes shows optical isomerism?
- A) [Co(NH₃)₆]³⁺
- B) [Cr(en)₃]³⁺
- C) [Fe(CN)₆]³⁻
- D) [Ni(CO)₄]
Answer & Explanation
Correct Answer: B) [Cr(en)₃]³⁺
Tris(ethylenediamine) complexes can exist as non-superimposable mirror images (optical isomers). Other complexes listed do not show optical activity.
18. Which of the following has the highest ionic character?
- A) NaCl
- B) MgCl₂
- C) AlCl₃
- D) BeCl₂
Answer & Explanation
Correct Answer: A) NaCl
NaCl has the highest ionic character due to the large difference in electronegativity between Na and Cl. AlCl₃ and BeCl₂ show significant covalent character.
19. Which of the following is used as a moderator in nuclear reactors?
- A) Graphite
- B) Lead
- C) Sodium
- D) Mercury
Answer & Explanation
Correct Answer: A) Graphite
Graphite slows down fast neutrons, acting as a moderator in nuclear reactors. Heavy water is another common moderator.
20. Which of the following is a non-benzenoid aromatic compound?
- A) Benzene
- B) Naphthalene
- C) Tropolone
- D) Anthracene
Answer & Explanation
Correct Answer: C) Tropolone
Tropolone is aromatic but does not contain a benzene ring, making it a non-benzenoid aromatic compound.
21. Which of the following has the highest lattice energy?
- A) NaCl
- B) KCl
- C) MgO
- D) CaO
Answer & Explanation
Correct Answer: C) MgO
MgO has the highest lattice energy due to the small ionic radii and high charges (+2 and -2). Lattice energy increases with charge and decreases with ionic size.
22. Which of the following is used in the estimation of halogens?
- A) Volhard method
- B) Mohr’s method
- C) Carius method
- D) Kjeldahl method
Answer & Explanation
Correct Answer: C) Carius method
Carius method is used for halogen estimation by oxidizing the compound with fuming nitric acid in a sealed tube.
23. Which of the following is a pseudo-first-order reaction?
- A) Hydrolysis of ester in acidic medium
- B) Decomposition of N₂O₅
- C) Radioactive decay
- D) Neutralization reaction
Answer & Explanation
Correct Answer: A) Hydrolysis of ester in acidic medium
Although ester hydrolysis is bimolecular, the concentration of water is very large and treated as constant, making the reaction pseudo-first-order.
24. Which of the following is a greenhouse gas with the highest global warming potential?
- A) CO₂
- B) CH₄
- C) N₂O
- D) SF₆
Answer & Explanation
Correct Answer: D) SF₆
Sulfur hexafluoride (SF₆) has an extremely high global warming potential, much greater than CO₂, CH₄, or N₂O.
25. Which of the following is used in the determination of nitrogen content in organic compounds?
- A) Carius method
- B) Kjeldahl method
- C) Volhard method
- D) Dumas method
Answer & Explanation
Correct Answer: B) Kjeldahl method
Kjeldahl method is widely used for nitrogen estimation in organic compounds by converting nitrogen to ammonium sulfate and then titrating.