Question

Predict the standard cell potential and calculate the standard reaction Gibbs free energy for galvanic cells having the following cell reactions:
a.)3Zn + 2Bi3+ = 3Zn2+ + 2Bi
b.)2H2 + O2 = 2H20 in acidic solution
c.)2H2 + O2 = 2H20 in basic solution
d.)3Au+ = 2Au + Au3+

I tried all of them and I could not figure any of them out. I am so confused. Thanks in advance.

Answer 1

You will find Zn^2+ + 2e ==> Zn in the standard reduction tables. You want the reverse of this so simply change the sign.
Then look up Bi^3+ + 3e ==> Bi
Zn number (with changed sign) + Bi number = Eocell.
Then dG = -nEF
n in this case is 6, E is from above, F is 96,485 coulombs.