For a given galvanic cell, the standard cell potential can be calculated by subt

Question

For a given galvanic cell, the standard cell potential can be calculated by subtracting standard half-cell potential of the reaction that occurs at the cathode from the standard half-cell potential of the reaction that occurs at the anode: E_cell = E_red (reduction process) - E_red (oxidation process) Tarnish on silver is the compound Ag_2O. A tarnished silver spoon is placed in an aluminum pan of boiling water. When enough salt is added so that the solution conducts electricity the tamish disappears. Imagine that the two halves of this redox reaction reaction were separated and connected with a wire and a salt bridge. Calculate the standard cell potential given the following standard reduction potentials: A1^3 + 3e^- rightarrow Al; E' = -1.66 V Ag^+ + e^- rightarrow Ag; E' = 0.799 V Express your answer to two decimal places and include the appropriate units.

Explanation / Answer

consider the given half reactions

Al+3 + 3e- --> Al Eo = -1.66 V

Ag+ + e- ---> Ag Eo = 0.799 V

now

we know that

the one with higher reduction potential is cathode

and

the one with less reduction potential is anode

aslo

oxidation takes place at anode

reduction takes place at cathode

so in this case

cathode : reduction

Ag+ + e- ---> Ag

anode : oxidation

Al ---> Al+3 + 3e-

now

we know that

Eo cell = Eo cathode - Eo anode

Eo cell = Eo Ag+/Ag - Eo Al+3/Al

Eo cell = 0.799 - ( -1.66)

Eo cell = 2.459

so

the value of Eo cell is 2.459 V

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