Question

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

Answer 1

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"`,