JAMB Chemistry 1982 Question 38

Question 38

Sulphur and its Compounds

Which of the following equations represents an oxidizing action of sulphur dioxide?

A.SO₂ + 2HNO₃ → H₂SO₄ + 2NO₂ + heat
B.2SO₂ + 2H₂O + O₂ → 2H₂SO₄
C.SO₂ + 2H₂O + Cl₂ → H₂SO₄ + 2HCl
D.SO₂ + 2H₂S → 3S + 2H₂O
E.K₂Cr₂O₇ + H₂SO₄ + 3SO₂ → K₂SO₄ + Cr₂(SO₄)₃ + H₂O.

Show the answer and explanation

Answer: D (SO₂ + 2H₂S → 3S + 2H₂O)

Explanation

With H₂S, the sulphur in SO₂ drops from +4 to 0, so SO₂ is reduced and acts as the oxidizing agent. In the other equations SO₂ is oxidised to sulphate.