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A galvanic cell is made up of solid In in 0.10 M In(NO3 )3 and solid Zn in 0.0050 M Zn(NO3 )2. The measured cell potential for this cell is 0.47 volts, when the zinc electrode operates as the anode. Find the standard reduction potential for: In3+ (aq) + 3e- → In(s) Given that Zn2+ + 2e- → Zn -0.76 V

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Answer:

-0.303 V

Explanation:

From Nernst equation

[In3+] =0.10 M

[Zn2+]=Zn in 0.0050 M

n= 6

E= 0.47V

Thus

E= E°- 0.0592/n log [Red]/[Ox]

0.47= E° - 0.0592/6 log 0.10/0.0050

0.47= E° - 0.0128

E°= 0.47- 0.0128

E°= 0.457 V

But

E°cell= E° cathode- E°anode

E°cathode= E°cell + E°anode

Hence

E°cathode= 0.457 + ( -0.76)

E°cathode= -0.303 V