To write a complete balanced reaction of a redox reaction, we need to know the half reactions of the molecules involved in the reaction and to balance these reactions. From, the problem statement ClO2- is oxidized to ClO4- so the half reaction would be:
(ClO)2- = (ClO)4-
To balance,
We first balance the elements except O and H in the reaction.
(ClO2)- = (ClO4)-
Then, we balance O by adding H2O and balance H by adding H+
(ClO2)- + 2H2O = (ClO4)- + 2H+
Then, we balance the charges by adding electrons,
(ClO2)- + 2H2O = (ClO4)- + 2H+ + e-
Then for Ag+ to Ag,
Ag+ = Ag
We just need to balance the charge,
Ag+ + e- = Ag
To determine the final equation, we add both half reactions:
(ClO2)- + 2H2O = (ClO4)- + 2H+ + e-
Ag+ + e- = Ag
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ClO2- +Ag+ +2H2O---> ClO4^- + Ag + 2H+
