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JAMB Chemistry 1984 Question 14

Question 14

Redox Reactions

In which of the following reactions does hydrogen peroxide act as a reducing agent?

  1. A.H2S + H2O2 → S + 2H2O
  2. B.PbSO3 + H2O2 → PbSO4 + H2O
  3. C.2I− + 2H+ + H2O2 → I2 + 2H2O
  4. D.PbO2 + 2HNO3 + H2O2 → Pb(NO3)2 + 2H2O + O2
  5. E.SO2 + H2O2 → H2SO4
Show the answer and explanation

Answer: D (PbO2 + 2HNO3 + H2O2 → Pb(NO3)2 + 2H2O + O2)

Explanation

A reducing agent is itself oxidised. In D, H2O2 is oxidised to O2 while PbO2 (lead +4) is reduced to Pb(NO3)2 (lead +2). In the others H2O2 is reduced to water, so it is the oxidising agent.