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

1 Answer
May 3, 2017

Answer:

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"#,