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JAMB Chemistry 1982 Question 12

Question 12

Hydrocarbons

How many grams of methylacetylene (propyne) CH3—C≡CH will completely discharge the colour of 8 g of bromine? (Br = 80, C = 12, H = 1)

  1. A.0.5
  2. B.1.0
  3. C.2.0
  4. D.3.0
  5. E.4.0
Show the answer and explanation

Answer: B (1.0)

Explanation

8 g Br2 = 8/160 = 0.05 mol. A triple bond adds two Br2, so 0.025 mol propyne is needed: 0.025 × 40 = 1.0 g.