Voltage and Balancing Redox Equations

[Giselle1B]

Why do you need the largest positive voltage as an answer for half reactions?

[Sean Reyes 1J]

You would need the largest positive voltage of as a result of both the half-reactions combined due to the fact that the potential difference comes from the maximum potential that can be produced. This maximum potential difference is represented by the E(cell).
Additionally, the E(cell) must be positive as a result of the relationship between Gibb's free energy and the E(cell). As E(cell) remains positive, the value of delta G will be negative, indicating a spontaneous reaction.
In other words, the cell potential (E(cell)) is derived from the maximum and must be positive, meaning that the cell potential must be the largest positive voltage.

[Matthew Mar 1J]

Also, in a more practical sense, if we think of the cell as a battery we know we want the work done by the battery to be at a maximum and the Wmax that a cell can do will be equal to the max potential difference.