Q61. Which of the following compounds of carbon is used as a refrigerant?
A) Carbon dioxide
B) Methane
C) Carbon tetrafluoride
D) Freon-12
Answer: D) Freon-12
Explanation: Freon-12 (CCl₂F₂) is a chlorofluorocarbon (CFC) that was used as a refrigerant. However, its use has been reduced due to its harmful effects on the ozone layer.
Q62. The hybridization of carbon in acetylene (C₂H₂) is:
A) sp
B) sp²
C) sp³
D) None of the above
Answer: A) sp
Explanation: In acetylene (C₂H₂), carbon forms a triple bond, leading to sp hybridization with two pi bonds and one sigma bond.
Q63. The stability of carbon compounds is mainly due to:
A) High bond energy of C-C bonds
B) High electronegativity of carbon
C) Ability to form multiple bonds
D) All of the above
Answer: D) All of the above
Explanation: Carbon compounds are stable due to the high bond energy of C-C bonds, its moderate electronegativity, and its ability to form multiple bonds (like C=C and C≡C).
Nitrogen Family (Group 15)
Q64. The most stable allotrope of phosphorus is:
A) White phosphorus
B) Red phosphorus
C) Black phosphorus
D) Violet phosphorus
Answer: B) Red phosphorus
Explanation: Red phosphorus is the most stable allotrope of phosphorus at room temperature, whereas white phosphorus is more reactive and less stable.
Q65. Which of the following nitrogen oxides is a colorless gas?
A) N₂O
B) NO₂
C) N₂O₃
D) N₂O₅
Answer: A) N₂O
Explanation: Nitrous oxide (N₂O), commonly known as laughing gas, is a colorless gas, while other nitrogen oxides like NO₂ are colored gases.
Q66. Ammonia (NH₃) is a:
A) Strong acid
B) Weak base
C) Strong base
D) Weak acid
Answer: B) Weak base
Explanation: Ammonia is a weak base due to its ability to accept a proton (H⁺) in water, forming ammonium ions (NH₄⁺) and hydroxide ions (OH⁻).
Q67. Phosphorus pentoxide (P₂O₅) reacts with water to form:
A) Phosphoric acid
B) Phosphorous acid
C) Hypophosphoric acid
D) Pyrophosphoric acid
Answer: A) Phosphoric acid
Explanation: Phosphorus pentoxide reacts with water to form phosphoric acid (H₃PO₄) through the following reaction:
P2O5+3H2O→2H3PO4P2O5+3H2O→2H3PO4
Q68. Which of the following is used in the manufacture of nitric acid?
A) Ammonia
B) Nitrogen
C) Nitrous oxide
D) Phosphine
Answer: A) Ammonia
Explanation: Nitric acid is produced through the Ostwald process, where ammonia (NH₃) is oxidized to nitric acid (HNO₃) using oxygen and a platinum catalyst.
Q69. Which of the following has the highest boiling point?
A) NH₃
B) PH₃
C) AsH₃
D) SbH₃
Answer: A) NH₃
Explanation: Ammonia (NH₃) has the highest boiling point among the hydrides of Group 15 due to the presence of strong hydrogen bonds.
Q70. The oxidation state of nitrogen in nitrous oxide (N₂O) is:
A) +1
B) +2
C) +3
D) +4
Answer: A) +1
Explanation: In N₂O (nitrous oxide), nitrogen has an oxidation state of +1, with one nitrogen atom in a 0 oxidation state and the other in a +2 state, giving an average of +1.
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