Q81. Phosphorus pentachloride (PCl₅) behaves as an ionic compound in:
A) Solid state
B) Liquid state
C) Gaseous state
D) Aqueous solution
Answer: A) Solid state
Explanation: In the solid state, PCl₅ exists as an ionic compound consisting of PCl₄⁺ and PCl₆⁻ ions. In the gaseous and liquid states, it exists as discrete PCl₅ molecules.
Q82. The only noble gas compound of nitrogen is:
A) XeF₄
B) XeF₆
C) XeO₄
D) XeONF
Answer: D) XeONF
Explanation: Xenon oxynitride fluoride (XeONF) is one of the few known compounds containing both nitrogen and a noble gas (xenon).
Q83. Which of the following is not a property of black phosphorus?
A) It has a layered structure.
B) It is a good conductor of electricity.
C) It is more stable than white phosphorus.
D) It is highly reactive.
Answer: D) It is highly reactive.
Explanation: Black phosphorus is the least reactive allotrope of phosphorus, unlike white phosphorus, which is highly reactive. It has a layered structure and is more stable.
Q84. Carbon tetrachloride (CCl₄) is widely used as a:
A) Solvent for organic compounds
B) Fertilizer
C) Reducing agent
D) Refrigerant
Answer: A) Solvent for organic compounds
Explanation: Carbon tetrachloride is a non-polar solvent used to dissolve non-polar organic compounds. However, its use has declined due to its toxicity and environmental impact.
Q85. Which of the following pairs of oxides are amphoteric?
A) CO₂ and SiO₂
B) Al₂O₃ and SnO₂
C) PbO₂ and CO
D) NO₂ and N₂O₅
Answer: B) Al₂O₃ and SnO₂
Explanation: Both aluminium oxide (Al₂O₃) and tin dioxide (SnO₂) are amphoteric, meaning they can react with both acids and bases.
Q86. Diborane (B₂H₆) contains:
A) Two three-center two-electron bonds
B) Two three-center three-electron bonds
C) Two three-center four-electron bonds
D) Two four-center two-electron bonds
Answer: A) Two three-center two-electron bonds
Explanation: Diborane contains two three-center two-electron (3c–2e) bonds, also known as banana bonds, which involve two boron atoms and one hydrogen atom sharing two electrons.
Q87. Which of the following oxides of nitrogen is paramagnetic?
A) N₂O
B) NO
C) NO₂
D) N₂O₅
Answer: B) NO
Explanation: Nitric oxide (NO) is paramagnetic due to the presence of an unpaired electron, while other nitrogen oxides are diamagnetic.
Q88. Which of the following elements of Group 13 is a metalloid?
A) Boron
B) Aluminium
C) Gallium
D) Indium
Answer: A) Boron
Explanation: Boron is a metalloid, possessing both metallic and non-metallic properties. Other Group 13 elements, such as aluminium and gallium, are metals.
Q89. The chemical formula of borax is:
A) Na₂B₄O₇·10H₂O
B) Na₂B₂O₅·5H₂O
C) Na₂B₄O₅·5H₂O
D) Na₂B₆O₁₁·10H₂O
Answer: A) Na₂B₄O₇·10H₂O
Explanation: Borax has the chemical formula Na₂B₄O₇·10H₂O. It is a hydrate of sodium tetraborate and is used in cleaning and laundry detergents.
Q90. In the Contact process for the manufacture of sulfuric acid, the catalyst used is:
A) Manganese dioxide
B) Vanadium pentoxide
C) Platinum
D) Iron oxide
Answer: B) Vanadium pentoxide
Explanation: Vanadium pentoxide (V₂O₅) is used as a catalyst in the Contact process to oxidize sulfur dioxide (SO₂) to sulfur trioxide (SO₃), which is then converted to sulfuric acid.
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