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JAMB Chemistry 1989 Question 50

Question 50

Hydrocarbons

Three liquids X, Y and Z containing only hydrogen and carbon were burnt on a spoon. X and Y burnt with sooty flames while Z did not. Y is able to discharge the colour of bromine water whereas X and Z cannot. Which of the liquids would be aromatic in nature?

  1. A.X and Z
  2. B.Y
  3. C.X
  4. D.Z
Show the answer and explanation

Answer: C (X)

Explanation

Aromatic hydrocarbons have a high carbon content and burn with a sooty flame, but they do not decolourise bromine water. Y decolourises it, so it is an alkene or alkyne; X is the aromatic one.