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JAMB Chemistry 1995 Question 26

Question 26

Redox Reactions

Which of the following is a redox reaction?

  1. A.KCl(aq) + H2SO4(aq) → KHSO4(aq) + HCl(aq)
  2. B.2FeBr2(aq) + Br2(aq) → 2FeBr3(aq)
  3. C.3AgNO3(aq) + FeCl3(aq) → 3AgCl(aq) + Fe(NO3)3(aq)
  4. D.H2CO3(aq) → H2O(l) + CO2(g)
Show the answer and explanation

Answer: B (2FeBr2(aq) + Br2(aq) → 2FeBr3(aq))

Explanation

In B, iron goes from +2 to +3 (oxidized) and bromine from 0 to −1 (reduced). No oxidation numbers change in the other three reactions.