Boron Family
Q11. Boron hydrides, such as B₂H₆, exhibit unusual bonding known as:
A) Ionic bonding
B) Metallic bonding
C) Three-center two-electron bonds
D) Two-center two-electron bonds
Answer: C) Three-center two-electron bonds
Explanation: Boron in diborane (B₂H₆) exhibits electron-deficient bonding. The two boron atoms are bonded by hydrogen atoms using a three-center two-electron bond, which is characteristic of boron hydrides.
Q12. Which of the following reactions is used in the production of borax?
A) Boric acid is neutralized by sodium hydroxide
B) Boron reacts with hydrochloric acid
C) Colemanite reacts with sodium carbonate
D) Aluminium is reacted with boron trioxide
Answer: C) Colemanite reacts with sodium carbonate
Explanation: Borax (Na₂B₄O₇·10H₂O) is obtained by reacting colemanite (Ca₂B₆O₁₁·5H₂O) with sodium carbonate, leading to the formation of borax.
Q13. Which of the following statements about aluminium is false?
A) It is a good conductor of electricity.
B) It is more reactive than iron.
C) It forms a protective oxide layer.
D) It is a heavier metal than iron.
Answer: D) It is a heavier metal than iron.
Explanation: Aluminium is actually a lighter metal compared to iron. It is known for being light and strong, making it useful in industries like aviation.
Q14. Boric acid (H₃BO₃) behaves as a weak acid because:
A) It donates protons in water.
B) It accepts hydroxide ions.
C) It dissociates completely in water.
D) It is a strong electrolyte.
Answer: B) It accepts hydroxide ions.
Explanation: Boric acid acts as a Lewis acid by accepting OH⁻ ions from water rather than donating protons (H⁺). This reaction produces B(OH)₄⁻ ions and makes boric acid behave as a weak acid.
Q15. The most stable oxidation state of thallium is:
A) +1
B) +2
C) +3
D) +5
Answer: A) +1
Explanation: Thallium shows the +1 oxidation state as the most stable due to the inert pair effect, where the 6s electrons are reluctant to participate in bonding.
Q16. Which of the following statements is true for the compounds of aluminium?
A) Aluminium oxide is amphoteric.
B) Aluminium chloride exists as a dimer in the gas phase.
C) Aluminium has low ionization energy compared to boron.
D) All of the above.
Answer: D) All of the above
Explanation: Aluminium oxide (Al₂O₃) is amphoteric, reacting with both acids and bases. In the gas phase, AlCl₃ exists as a dimer (Al₂Cl₆) to satisfy the octet rule. Aluminium has lower ionization energy compared to boron due to its larger atomic size.
Carbon Family
Q17. The general oxidation states shown by the elements of Group 14 are:
A) +1 and +2
B) +2 and +3
C) +4 and +2
D) +3 and +5
Answer: C) +4 and +2
Explanation: Group 14 elements exhibit +4 oxidation states as their primary oxidation state, but as we go down the group, the +2 oxidation state becomes more stable due to the inert pair effect.
Q18. Carbon tetrachloride (CCl₄) does not hydrolyze easily because:
A) Carbon is not reactive.
B) Chlorine atoms are strongly bonded to carbon.
C) Carbon does not have vacant d-orbitals.
D) Water does not react with non-polar compounds.
Answer: C) Carbon does not have vacant d-orbitals.
Explanation: Carbon lacks vacant d-orbitals to accept lone pairs from water, so CCl₄ does not hydrolyze easily. In contrast, silicon tetrachloride (SiCl₄) hydrolyzes because silicon has vacant d-orbitals.
Q19. Which of the following shows the highest tendency for catenation?
A) Silicon
B) Carbon
C) Germanium
D) Tin
Answer: B) Carbon
Explanation: Carbon’s ability to form long chains and rings (catenation) is due to its strong C-C bonds and small size, making it the most prominent element for catenation among Group 14.
Q20. Diamond has a high melting point because:
A) It is a molecular solid.
B) It is made of ionic bonds.
C) It has a three-dimensional network of covalent bonds.
D) It contains weak van der Waals forces.
Answer: C) It has a three-dimensional network of covalent bonds.
Explanation: Diamond consists of a three-dimensional lattice where each carbon atom is covalently bonded to four other carbon atoms, giving it exceptional hardness and a high melting point.
Leave a comment