Electrochemical cell -- potential ?? help?
(a) What is the potential of this cell at 25°C if the aluminum electrode is placed in a solution in which [Al3+] = 7.1 10-3 M?
Answer:
You need the reduction potentials of Ni(2+) and Al(3+). Their difference is the cell voltage at standard conditions. You then use the Nernst Equation to get eh potential at the non-standard aluminum concentration.
Ni2+ + 2e- >> Ni E° = - 0.257 V
Al3+ + 3e- >> Al E° = - 1.676 V
The reaction that occurs is
2Al +3 Ni2+ >> 2Al3+ +3 Ni
E(Ni) = - 0.257 + 0.059/ 2 log 1.0 = - 0.257
E (Al) = - 1.676 + 0.059/3 log 7.1x10^-3 = -1.72
E = +1.72 -0.257 = 1.46 V
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