Take C = 12, H = 1, Cl = 35.5. What is the percentage by mass of chlorine in PVC, whose repeat unit is –CH₂–CHCl–?
Correct answer D. 56.8%
Explanation
Molar mass of the repeat unit C₂H₃Cl = 24 + 3 + 35.5 = 62.5 g/mol. Percentage of chlorine = (35.5/62.5) × 100 = 56.8%, which is the same for any chain length.
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