Boron Family (Group 13)
Q51. Aluminium reacts with atmospheric oxygen to form a protective layer of:
A) Al₂O₃
B) Al(OH)₃
C) AlO₃
D) Al₂O₄
Answer: A) Al₂O₃
Explanation: Aluminium forms a protective oxide layer of Al₂O₃ when exposed to air. This layer prevents further oxidation and corrosion of the metal.
Q52. Which of the following compounds of boron is used as a neutron absorber in nuclear reactors?
A) Boric acid
B) Boron nitride
C) Borax
D) Diborane
Answer: A) Boric acid
Explanation: Boric acid is used in nuclear reactors as a neutron absorber due to the high neutron-capturing ability of boron-10 isotope, which helps control the fission reaction.
Q53. The compound BF₃ behaves as:
A) A Lewis base
B) A Lewis acid
C) A strong electrolyte
D) A strong base
Answer: B) A Lewis acid
Explanation: BF₃ is an electron-deficient compound with only six electrons around boron, so it readily accepts electrons, making it a Lewis acid.
Q54. Which of the following boron halides is the least volatile?
A) BF₃
B) BCl₃
C) BBr₃
D) BI₃
Answer: D) BI₃
Explanation: The volatility decreases down the group with increasing molecular mass. BI₃ is the least volatile because of its large atomic size and stronger van der Waals forces.
Q55. What is the hybridization of boron in boric acid (H₃BO₃)?
A) sp
B) sp²
C) sp³
D) dsp²
Answer: B) sp²
Explanation: In boric acid, boron is surrounded by three oxygen atoms, and the geometry is trigonal planar, which corresponds to sp² hybridization.
Q56. Which of the following is a correct statement about the electronic configuration of aluminium?
A) [Ne] 3s² 3p¹
B) [Ar] 4s² 4p¹
C) [Ne] 3s² 3p²
D) [He] 2s² 2p¹
Answer: A) [Ne] 3s² 3p¹
Explanation: Aluminium has 13 electrons. The correct electronic configuration is [Ne] 3s² 3p¹.
Carbon Family (Group 14)
Q57. The allotrope of carbon that is a good conductor of electricity is:
A) Diamond
B) Graphite
C) Fullerene
D) Carbon nanotubes
Answer: B) Graphite
Explanation: Graphite conducts electricity because its structure consists of layers of carbon atoms with free-moving delocalized electrons between the layers.
Q58. The most stable oxide of carbon is:
A) CO₂
B) CO
C) C₂O
D) C₂O₃
Answer: A) CO₂
Explanation: Carbon dioxide (CO₂) is the most stable oxide of carbon. Carbon monoxide (CO) is less stable due to its partial oxidation state.
Q59. Silicon carbide (SiC) is commonly used as:
A) A semiconductor
B) A reducing agent
C) An abrasive
D) A fertilizer
Answer: C) An abrasive
Explanation: Silicon carbide (SiC), also known as carborundum, is extremely hard and is used as an abrasive material for cutting and grinding.
Q60. The inert pair effect is more prominent in which of the following elements?
A) Carbon
B) Silicon
C) Germanium
D) Lead
Answer: D) Lead
Explanation: The inert pair effect becomes more prominent as you go down the group in Group 14 elements. In lead (Pb), the 6s² electrons are reluctant to participate in bonding, making the +2 oxidation state more stable than the +4 state.
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