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JAMB Chemistry 1985 Question 41

Question 41

Hydrocarbons

A colourless organic compound X was burnt in excess air to give two colourless and odourless gases, Y and Z, as products. X does not decolorize bromine vapour, Y turns lime milky while Z gives a blue colour with copper (II) tetraoxosulphate (VI). Compound X is

  1. A.an alkene
  2. B.an alkane
  3. C.an alkyne
  4. D.tetrachloromethane
  5. E.dichloromethane
Show the answer and explanation

Answer: B (an alkane)

Explanation

Burning gives only CO2 (turns limewater milky) and water (turns anhydrous CuSO4 blue), so X is a hydrocarbon. It does not decolourise bromine, so it is saturated: an alkane.