Q71. Phosphine (PH₃) is:
A) A reducing agent
B) An oxidizing agent
C) Amphoteric
D) Neutral
Answer: A) A reducing agent
Explanation: Phosphine (PH₃) acts as a reducing agent because phosphorus can be easily oxidized due to its low electronegativity and weak P-H bonds.
Q72. The bond angle in phosphine (PH₃) is less than ammonia (NH₃) because:
A) Phosphorus is larger than nitrogen
B) Lone pair-lone pair repulsion is greater in PH₃
C) Electronegativity of phosphorus is lower
D) The molecular size of PH₃ is smaller
Answer: C) Electronegativity of phosphorus is lower
Explanation: The lower electronegativity of phosphorus compared to nitrogen causes less electron repulsion in the P-H bonds, resulting in a smaller bond angle in PH₃ than in NH₃.
Q73. The element that shows the greatest tendency to form pπ–pπ multiple bonds is:
A) Nitrogen
B) Phosphorus
C) Arsenic
D) Antimony
Answer: A) Nitrogen
Explanation: Nitrogen, being the smallest in size among Group 15 elements, forms strong pπ–pπ multiple bonds such as N≡N in nitrogen gas (N₂), due to its ability to overlap efficiently.
Q74. The compound N₂O₃ is:
A) Acidic
B) Basic
C) Neutral
D) Amphoteric
Answer: A) Acidic
Explanation: Nitrogen trioxide (N₂O₃) is an acidic oxide. When dissolved in water, it forms nitrous acid (HNO₂).
Q75. Which of the following statements is correct about boron nitride (BN)?
A) It is a good conductor of electricity.
B) It has a structure similar to graphite.
C) It is used as a fertilizer.
D) It is amphoteric.
Answer: B) It has a structure similar to graphite.
Explanation: Boron nitride exists in two forms: hexagonal BN, which has a structure similar to graphite, and cubic BN, which resembles diamond in structure.
Q76. In which of the following reactions does phosphorus act as an oxidizing agent?
A) P₄ + 3NaOH + 3H₂O → PH₃ + NaH₂PO₂
B) P₄ + 10Cl₂ → 4PCl₅
C) PCl₅ → PCl₃ + Cl₂
D) 2P + 3Cl₂ → 2PCl₃
Answer: B) P₄ + 10Cl₂ → 4PCl₅
Explanation: In this reaction, phosphorus (P) is oxidized from 0 to +5 oxidation state in PCl₅, thus acting as an oxidizing agent.
Q77. The highest oxidation state of nitrogen in its compounds is:
A) +3
B) +4
C) +5
D) +1
Answer: C) +5
Explanation: The highest oxidation state nitrogen can achieve is +5, as seen in compounds like nitric acid (HNO₃) and nitrogen pentoxide (N₂O₅).
Q78. Which of the following statements about urea is correct?
A) It is an acidic compound.
B) It contains an amide functional group.
C) It is used as a pesticide.
D) It is synthesized from ammonia and nitric acid.
Answer: B) It contains an amide functional group.
Explanation: Urea (NH₂CONH₂) contains two amide groups attached to a carbonyl group. It is widely used as a nitrogen fertilizer.
Q79. Which of the following elements has the highest first ionization energy?
A) Carbon
B) Nitrogen
C) Oxygen
D) Boron
Answer: B) Nitrogen
Explanation: Nitrogen has the highest first ionization energy due to its half-filled 2p orbitals, which provide extra stability.
Q80. Which of the following compounds is not a hydride of nitrogen?
A) Hydrazine (N₂H₄)
B) Ammonia (NH₃)
C) Hydroxylamine (NH₂OH)
D) Nitric acid (HNO₃)
Answer: D) Nitric acid (HNO₃)
Explanation: Nitric acid is an oxoacid of nitrogen, not a hydride. The others are all hydrides containing N-H bonds.
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