Answer:
Highest voltage is generated by the Ni°|Ni⁺²||Cu⁺²|Cu° Voltaic Cell in the amount of E°(cell) = 0.597 volt.
Step-by-step explanation:
The standard voltage of a voltaic cell can be calculated using the expression E°(cell) = E°(redn) - E°(oxdn).
The symbology of the voltaic cell is generally shown as
[ Oxdn Rxn || Redn Rxn ].
That is, for the cell Mn°|Mn⁺² || Zn⁺²|Zn° the reduction reactions (as given in the Table of Standard Reduction Potentials) are:
Mn⁺² + 2e⁻ => Mn°; E°(Mn⁺²|Mn°) = -1.17 volts
Zn⁺² + 2e⁻ => Zn° ; E°(Zn⁺²|Zn°) = -0.76 volts
Note => One can search engine 'Table of Standard Reduction Potentials'. A number of citations will be given.
Since in the symbolic cell the order is oxidation rxn || reduction rxn ; the manganese reaction should be reversed and added to the zinc reduction reaction giving the standard net cell reaction, E°(cell). That is ...
Oxidation Rxn: Mn° => Mn⁺² + 2e⁻
Reduction Rxn: Zn⁺² + 2e⁻ => Zn°
Net Cell Rxn: Mn° + Zn⁺² => Mn⁺² + Zn°
Therefore, the Standard Cell Potential for the Mn°|Mn⁺² || Zn⁺²|Zn° cell is ...
E°(cell) = E°(redn) - E°(oxdn) = E°(Zn°) - E°(Mn°) = (-0.76v) - (-1.17v) = 0.41 volt
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The cell potentials for the remaining cells are calculated the same way. That is ...
For the Zn°|Zn⁺² || Ni⁺²|Ni° cell
E°(Zn|Ni) = E°(Ni) - E°(Zn) = (0.257v) - (-0.76v) = 0.503 volt, and
For the Ni°|Ni⁺² || Cu⁺²|Cu° cell
E°(Ni|Cu) = E°(Cu) - E°(Ni) = (+0.34v) - (-0.257v) = 0.597 volt (highest voltage)
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NOTE => When using the Table of Standard Reduction Potentials it is useful to remember that the electron flow is always from the more negative voltage to the more positive voltage. That is, the element or polyion with more negative negative voltage is always the oxidation process while the more positive voltage is always the reduction process.
Also, when calculating the Standard Cell Potential the value determined must always be positive. Otherwise, the cell combination shown in the symbolic form will be a no reaction. (Good to know for questions like 'Which of the following will not occur?') That is E°(cell) = E°(redn) - E°(oxdn) > 0.00 volts.
Hope this helps. :-)