How to Figure out Relative Oxidizing Power of Molecules or Ions – Part 2

Redox or reduction–oxidation or oxidation–reduction (simultaneous) is a type of chemical reaction in which the oxidation states (OSs) of the reactants change.


Mnemonic: OIL RIG (Oxidation Is Loss, Reduction Is Gain)

Redox potential aka oxidation/reduction potential (ORP or Ered) is a measure of the tendency of a chemical species to gain electrons from or lose electrons to an electrode; and therefore, be reduced or oxidized respectively.

As per the IUPAC (international union of pure and applied chemistry), standard electrode potential (EѲ) is the value of the standard emf (electromotive force) of a cell in which molecular hydrogen under standard pressure is oxidized to solvated protons at the left-hand electrode.

Question:

Why is the EѲ value for the Mn3+/Mn2+ couple much more positive than that for Cr3+/Cr2+ or Fe3+/Fe2+?

Solution:



Click/tap to enlarge the image

Ionization energy/enthalpy/potential (IE) is the minimum energy required to remove the most labile electron(s) (the valence electron(s)) of an isolated gaseous atom, positive ion, or molecule.

This also explains why the +3 state of Mn is of little importance.

Raffishly redox❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Ncert. Chemistry : Textbook for Class XII - Part.I; National Council Of Educational Research And Training: New Delhi.

‌(2)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

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