Answer to Question #110163 in General Chemistry for Shealyn

Question

Which ion is more easily oxidized in aqueous solution Cl- or Br-? Why?

Answer 1

Electronegativity (i.e. electron affinity) decreases down by the group. The most electronegative atom is F, then by the group goes Cl, Br and I. The more atom's electronegativity the more it's stable with electron attached (in anion form), so Cl^- is more stable than Br^-. It means that it's easier to oxidize Br^- than Cl^-.

Reference data is $E^0_{Cl_2/Cl^-}\approx1.36$ V > $E^0_{Br_2/Br^-}\approx1.08$ V, which is consistent with the above points