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JAMB Chemistry 1998 Question 28

Question 28

Electrolysis

Mg2+(aq) + 2e− → Mg(s) E° = −2.370 volts
Zn2+(aq) + 2e− → Zn(s) E° = −0.763 volts
Cd2+(aq) + 2e− → Cd(s) E° = −0.403 volts
Cu2+(aq) + 2e− → Cu(s) E° = +0.340 volts
In the electrochemical series above, the strongest reducing agent is

  1. A.Cu(s)
  2. B.Cd(s)
  3. C.Zn(s)
  4. D.Mg(s)
Show the answer and explanation

Answer: D (Mg(s))

Explanation

The metal with the most negative electrode potential gives up electrons most easily, so it is the strongest reducing agent. Magnesium (−2.37 V) is strongest; copper (+0.34 V) is the weakest.