Empirical formula simplifies molecular formula ratios Steps:

• Examine the skeletal formula of phenazine, a tricyclic aromatic compound with two fused benzene rings and a central pyrazine ring.
• Count atoms: 12 carbon, 8 hydrogen, 2 nitrogen atoms.
• Obtain molecular formula C₁₂H₈N₂.
• Divide subscripts by greatest common divisor (2) to get simplest ratio: C₆H₄N.

Why B is correct:

• Empirical formula is the lowest whole-number ratio of elements; C₁₂H₈N₂ reduces to C₆H₄N by dividing by 2.

Why the others are wrong:

• A: C₄H₄N ratio (4:4:1) does not match phenazine's 6:4:1 atom ratio.
• C: C₁₂H₈N₂ is the full molecular formula, not simplified.
• D: C₁₂H₈N omits one nitrogen, undercounting heteroatoms in the structure.

Final answer: B