How is the reaction between hydrogen sulfide and iron chloride possible?

1 Answer
Ernest Z.
May 3, 2017

The reason has nothing to do with electronegativity.

Explanation:

Electronegativity is a measure of the attraction a neutral atom has for the shared electrons in a covalent bond

The reason has more to do with the relative energies of the two iron ions.

"Fe"^"2+""(g)" → "Fe"^"3+" "(g)" + "e"^"-" ; I_3 ≈ "3000 kJ/mol"

The third ionization energy of "Fe" is quite high, so "Fe"^"3+" is much less stable than "Fe"^"2+".

In aqueous solution, "Fe"^"3+" is slightly more stabilized by hydration than "Fe"^"2", but that does not compensate for the high 3rd ionization energy.

In short, "Fe"^"3+" is less stable than "Fe"^"2+" and would like having another electron to reduce the charge.

Thus, "Fe"^"3+" is quite capable of removing an electron from "H"_2"S",

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