Solve Galvanic Cell: 0.050M Cu2+, AlCl3 0.0118M

[reising1]

Homework Statement

Consider a Galvanic Cell composed of one half-cell containing 0.050 M copper(II) sulfate with a copper electrode and another half-cell containing an unknown concentration of aluminum chloride, AlCl3, and an aluminum electrode.

a. Write the Nernst equation for this galvanic cell, replacing as many variables as possible with numbers.
b. What concentration of AlCl3 would be necessary for the log term in the Nernst equation to equal zero.

The Attempt at a Solution

a. 2Al + 3Cu2+ -> 2Al3+ + 3Cu
Delta E standard = E(cathode) - E(anode) = .3402 - -1.706 = 2.0462

Delta E = E standard - .05917 / n (log Q)
Delta E = 2.0462 - (.05915/6) log( (Al3+)^2 / (Cu2+)^3 )

b. log( (Al3+)^2 / (Cu2+)^3 ) = 0
(Al3+)^2 / (Cu2+)^3 = 1
(Al3+)^2 / (.05)^3 = 1
Al3+ = .0118 M

Is this correct?

 

[Borek]

Looks OK at first sight, but I can be missing something.

I don't like the idea of Al electrode in water. Al is reactive enough to displace hydrogen from water, plus it is always covered with oxide, so calculating electrode potential as if it was any other metal is a waste of time and has nothing to do with reality.