Electrochemical cells

[ana111790]

Homework Statement

Based on the following chart, what ions would you use to construct an electrochemical cell with potential closest to 2.00 V?

[PLAIN]http://img546.imageshack.us/img546/5568/electrochemicalcellchar.png [Broken]

Homework Equations

I know that I am supposed to add the voltages of the 2 reactions but I am not sure how the signs would go. We are not using a textbook for this class so I have nothing to reference.

The Attempt at a Solution

I'd use the following reactions and voltages
Fe3+ -> Fe2+ (-0.771 gaining electron)
Na (s) -> Na+ (+2.71 losing electron)

so the cell voltage would be 1.94V. Is this correct?

 

[Borek]

Think about simple math - what is the distance between -2.7 and +0.7 points?

 

[ana111790]

Thank you, that was very helpful!