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# Balancing a Reduction-Oxidation Reaction

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Use the following pair of reduction half-reactions to design a galvanic cell. Then write in the proper coefficient for each of the species involved in the overall reaction. Water molecules and protons are not shown in the half-reactions, but may be needed in the overall reaction.
MnO4- (aq) --> MnO2 (s) Eo = 0.59 V
NO3- (aq) --> NO (g) Eo = 0.96 V

What are the proper coefficients for each of the following:
NO3- (aq), MnO4- (aq), NO (g), MnO2 (s), H+ (aq), H2O (l)

https://brainmass.com/chemistry/electrochemical-cells/balancing-reduction-oxidation-reaction-231451

#### Solution Preview

To start this problem, you need to look at the half-reactions individually:

1) Balance the half-reactions:

MnO4- (aq)  MnO2 (s)
Add 2 H2O molecules to balance the O
MnO4- (aq)  MnO2 (s) + 2 H2O (l)
Add 4 H+ ions to balance the H
MnO4- (aq) + 4 H+ (aq)  MnO2 (s) + 2 H2O (l)
Balance the charges by adding 3 e-
MnO4- (aq) + 4 H+ (aq) + 3 e-  MnO2 (s) + 2 H2O ...

#### Solution Summary

This solution explains how to balance a reduction-oxidation reaction by adding H+, electrons, and water so that the combined half-reactions are balanced..

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