Chemistry question-electrochem

Question

An electrochemical cell consists of a nickel metal electrode immersed in a solution with [Ni^2 ]=1.0 M separated by a porous disk from an aluminum metal electrode immersed in a solution with [Al^3 ]=1.0 M. Sodium hydroxide is added to the aluminum compartment causing Al(OH)3(s) to precipitate. After precipitationof Al(OH)3 has ceased, the cell potential is 1.82 V. Calculate Ksp for Al(OH)3.

Al(OH)3(s)<---> Al^3 (aq) 3OH-(aq) Ksp=?

Answer 1

Ni+2 &amp; 2e- --&gt; Ni ......... Eo = - 0.28 volts

Al --&gt; Al+3  &amp; 3 e-  ...... Eo = +1.66 volts

cell poteltial was 1.38 volts

if after precipitation of Al(OH)3 has ceased, the cell potential is 1.82 V,

then :

1.82 plus 0.28 (Ni+2 &amp; 2e- --&gt; Ni was Eo = -0.28)=  2.10 volts ...  then

the cell potential for  Al  &amp;  3OH-  --&gt; Al(OH)3 &amp; 3 e-  E = 2.10 volts

if:

Al(OH)3 &amp; 3 e-  ---&gt; Al  &amp;  3OH-  ..... Eo = - 2.10

Al --&gt; Al+3  &amp; 3 e-  ...... Eo = +1.66 volts

combining gives:

Al(OH)3(s)&lt;---&gt; Al+3  &amp;   3OH-   ... Eo = -0.44

log K = (Eo) (n) / 0.0592

log K = (-0.44) (3) / 0.0592

log K = - 22.30

K = 5.01e-23

I don&#039;t like my answer.  

Are you sure of the &quot;1.82 volts&quot; ?

I would have rather it had been about 2.03 volts.

that gives me a K = e-33