Question

Complete and balance the following redox equation. What is the coefficient of H₂O when the equation is balanced with the set of smallest whole-number coefficients?

H₂O +MnO₄^? + I^? ?MnO₂ + IO₃^? (basic solution)

Please explain how to do this problem using the half reaction method

Answer 1

Balnanced equation :

2 MnO₄^{-} (aq) + I^{-}(aq) + H₂O (l)--------------------> 2 MnO₂(aq) + IO₃^{-}(aq) + 2 OH^{-} (aq)

oxidation half reaction:

I-   ---------------------------> IO3-

(-1)                                   (+5)

oxygens balance

I-   + 6OH- -----------------------> IO3-

hydrogens balance

I-   + 6OH- -----------------------> IO3- + 3H2O   

charge balance

I-   + 6OH- -----------------------> IO3- + 3H2O --------------------(1)

reductionhalf reaction:

MnO4-   -------------------> MnO2

(+7)                                  (+4)

oxygens balance

MnO4-     -------------------> MnO2 + 4OH-   

hydrogen balance

MnO4-    +   + 2H2O -------------------> MnO2 + 4OH-

charge balance

MnO4-    +    2H2O -------------------> MnO2 + 4OH-   -------------(2)

by mulitiplying suitable number with 1 and 2 and add finally balanced equation

H₂O + 2 MnO₄^{-} + I^{-} --------------------> 2 MnO₂ + IO₃^{-} + 2 OH^{-}