Question

Please write down the redox reactions (using the half-reaction method!)

a)Cl2 from OCl- and Cl- in acidic solution

b)Br2 from BrO3- and Br- in acidic solution

-You don't have to do both, but could you help me step up the half reactions especially for OCl- --> Cl2

Answer 1

2 OCl^- + 2e + 4H^+ ==> Cl2 + 2H2O
2Cl^- ==> Cl2 + 2e

When you add these two you end up with twice the coefficients so divide everything by 2. I do it this way because it's easier to explain to students and then divide by 2; however, you can do it from the beginning by
OCl^- + e + 2H^+ ==> Cl + H2O
Cl^- ==> Cl + e
but students don't like to see atomic Cl because they always write it as Cl2. However, when you add the second equation 1 to the second equation 2 you end up with a Cl on the right with another Cl on the right and that makes Cl2.

Answer 2

Thank you so much! I understand now.