A Levels Chemistry (9701)•9701/13/M/J/22
Explanation
Empirical formula from molecular structure Steps:
- Examine the skeletal formula of phenazine, a tricyclic compound with two nitrogen atoms in fused benzene-like rings.
- Count the atoms: 12 carbon atoms, 8 hydrogen atoms, and 2 nitrogen atoms.
- Determine the molecular formula: C₁₂H₈N₂.
- Simplify to the lowest whole-number ratio by dividing each subscript by 2, yielding C₆H₄N.
Why B is correct:
- The empirical formula represents the simplest ratio of atoms present in the compound, which for phenazine is C₆H₄N.
Why the others are wrong:
- A (C₄H₃N): Incorrect ratio; does not match the 6:4:1 atom proportions.
- C (C₆H₅N): Wrong hydrogen count; phenazine has 4 H per 6 C and 1 N, not 5 H.
- D (C₁₂H₈N₂): This is the molecular formula, not the simplified empirical one.
Final answer: B
Topic: Nitrogen compounds
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