[saberdoom]

Use tabulated half-cell potentials to calculate ΔG∘rxn for each of the following reactions at 25 ∘C.

2Fe3+(aq)+3Sn(s)→2Fe(s)+3Sn2+(aq)

I think the formula I'm suppose to use it delta G standard = -n*F*E cell potential standard.

Fe3+ → Fe is .036 V cell potential standard

and

Sn2+ → Sn is -.14 V cell potential standard.

I got an over all cell potential standard of .094. However when I plug in the equation

-6 mol * 96.5 kj/mol * .094 = -54

What am I doing wrong?

[Corribus]

It's hard to say without seeing more details of your calculation.  How did you determine "over all cell potential"?