SPM Chemistry Form 5 Notes – Terminology and Concepts: Oxidation and Reduction (Part 5) – Correction

by BerryBerryTeacher

in Berry Reference (Notes)

There has been confusion over “electrochemical series” and “reactivity series“. This confusion had been made worse by some revision books which tend to put both of them as the same series. So BerryBerryEasy would like to make a clarification to those who might have been confused about this issue. The two series are not the same, so the previous post will be corrected and explanation will be given here to clear all doubts.

SPM Chemistry Form 5 – Terminology and Concepts: Oxidation and Reduction (Part 5 – Correction)
–> Difference between electrochemical series and reactivity series

Rusting of Iron Nails

Rusting of Iron Nails

Despite the confusion in some revision books, the electrochemical and reactivity series is not the same.

The reactivity series is about:

  • List of metals (sometimes with hydrogen and carbon added as baseline) arranged by the ability to reduce other chemicals in non-specific way.
  • The reactivity is dependent on the conditions of the reactions and all are relative.
  • So the order will be slightly different between various books and research. (However, generally it should be the same)
  • Reactivity series
    K, *Na, *Ca,  Mg, Al, Zn, Fe, Sn, Pb, Cu, Hg, Ag, Au
    <—- increase in reactivity of metals.
    Do take notes with the *, the position of the calcium and sodium are different. In electrochemical series, calcium is more electropositive than sodium but not for the reactivity series.

This is in contract with the electrochemical series :

  • List of reducing agents arranged by the way of negative potential in an electrochemical cell
  • The conditions are pressure of 1 atm, temperature of 298 K and molar concentration of 1.o M
  • The electrochemical series / electropositivity of metal
    Equilibrium Eɵ (volts)
    Li+ (aq) + e <—> Li (s) - 3.03
    K+ (aq) + e <—> K (s) - 2.92
    *Ca2+ (aq) + 2e <—> Ca (s) - 2.87
    *Na+ (aq) + e <—> Na (s) - 2.71
    Mg2+ (aq) + 2e <—> Mg (s) - 2.37
    Al3+ (aq) + 3e <—> Al (s) - 1.66
    Zn2+ (aq) + 2e <—> Zn (s) - 0.76
    Fe2+ (aq) + 2e <—> Fe (s) - 0.44
    Pb2+ (aq) + 2e <—> Pb (s) - 0.13
    2H+ (aq) + 2e <—> H2 (g) 0
    Cu2+ (aq) + 2e <—> Cu (s) + 0.34
    Ag+ (aq) + e <—> Ag (s) + 0.80
    Au3+ (aq) + 3e <—> Au (s) + 1.50

So, more IMPORTANTLY, the SPM syllabus focuses on the reactivity instead of electrochemical potentials, so do use the reactivity series instead of the electrochemical series.

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