whenSO2 is passed in a solution of potassium iodate, the oxidation state of iodine changes from :
+5 to 0
When SO2 gas is passed into a solution of KIO3, the products are I2, H2SO4 and K2SO4.
The balanced equation for the reaction is:
5+4S−2O2+4+1H2−2O+2+1K+5I−2O3⟶+1K2+6S−2O4+0I2++1H2+6S−2O4
As you can see, the I in the IO−3 has a +5 oxidation state, which is changed to 0 in I2