The disproportionation of chlorate ions is represented by the balanced equation 2ClO3−→2Cl−+3O2. Which option correctly states how the oxidation number of chlorine changes and identifies whether chlorine is oxidized or reduced?
a) from +5 to +7; chlorine is oxidized
b) from +3 to −1; chlorine is reduced
c) from +5 to −1; chlorine is reduced
d) from +5 to −1; chlorine is oxidized