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JAMB Chemistry 1981 Question 41

Question 41

Sulphur and its Compounds

When hydrogen sulphide and sulphur dioxide are each passed in turn into a solution of potassium dichromate

  1. A.both gases change the colour of the solution from yellow to colourless
  2. B.both gases cause sulphur to be deposited
  3. C.only hydrogen sulphide decolorizes the solution
  4. D.only sulphur dioxide deposits sulphur
  5. E.only hydrogen sulphide deposits sulphur.
Show the answer and explanation

Answer: E (only hydrogen sulphide deposits sulphur.)

Explanation

Both gases reduce the dichromate (orange to green), but only H2S is oxidised to solid sulphur; SO2 is oxidised to sulphate ions in solution.