Question

how do you balance this redox reaction? Cl2+OH^-=ClO3^-+Cl^-+H2O

Answer 1

I believe this how you do it:
For ones like this one of the Cl's in Cl2 is oxidized, one reduced, so write it as Cl + Cl or write it twice Cl2 + Cl2

Cl + Cl = ClO3- + Cl-

Cl = ClO3- + 5e-

Cl + 1e- = Cl-

so

Cl + 5Cl = ClO3- + 5Cl-

now add the OH- and H2O

Cl + 5Cl + 6OH- = ClO3- + 5Cl- + 3H2O

now put the Cl's back together

3Cl2 + 6OH- = ClO3- + 5Cl- + 3H2O