Balance Redox reaction

Question

How would you balance the following redox reaction using oxidation number method? (Not half reaction method). Also is this an example of a disproportion reaction? Thanks!

Cl2 ➡️ ClO3^- + Cl-

Answer 1

Yes, this is an example of a disproportionation reaction because Cl is being both oxidized and reduced.

Cl₂ ===> ClO₃^- + Cl^-

0...........+5...-2....-1.......oxidation numbers

1/2 Cl₂ + 1/2 Cl₂ ==> ClO₃^- + Cl^-

for oxidation, Cl goes from 0 to +5 (loss of 5 electrons)

for reduction Cl goes for 0 to -1 (gain of 1 electron)

Multiply the oxidation reaction by 5 to equalize electrons. You get...

1/2 Cl₂ + 5/2 Cl₂ ==> ClO₃^- + 5Cl^- which is the same as ..

3Cl₂ ==> ClO₃^- + 5Cl^-

Now balance the oxygens an hydrogens...(I chose to do this in acid media)

3Cl₂ + 3H₂O ==> ClO₃^- + 5Cl^- + 6H⁺ ... balanced reaction