[Ari Ben Canaan]

Page 7 Part (c) is where I'm having some doubts. The nickel question.

I believe that since the electrode potentials are quite negative (see below) then both Nickel and Iron will go into solution as ions.

Furthermore, only Nickel would be deposited at the Cathode due to its more positive potential relative to Iron.

Ni2+/Ni = –0.25V
Fe2+/Fe = –0.44V

However, the mark scheme seems to be implying that only the Fe goes into solution. This is what it says word for word :

Because the Fe potential is more negative than the Ni potential, the iron will dissolve

Am I correct ?

[Ari Ben Canaan]

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w10_qp_41.pdf


Link not working . Fixed above !

Page 7  Part c

[Borek]

Because the Fe potential is more negative than the Ni potential, the iron will dissolve

Where does it state nickel will not dissolve?

[Ari Ben Canaan]

Because the Fe potential is more negative than the Ni potential, the iron will dissolve

Where does it state nickel will not dissolve?

It seems to be almost hinting that it won't.... Its unclear.... Could you please confirm that my methodology and hence my answer is correct/wrong ?

I'd be very much obliged. 

[Borek]

Iron will dissolve first, nickel second, but I bet conditions are selected in such a way there are both dissolving at the same time. Controlling the reduction potential you can selectively deposit nickel, leaving iron in the solution.

Note that you can't dissolve iron selectively, no matter what. Once you dissolve iron that is in contact with the solution you are left with a nickel on the surface and the solution has no access to the iron in the bulk of the electrode.

[Ari Ben Canaan]

Iron will dissolve first, nickel second, but I bet conditions are selected in such a way there are both dissolving at the same time. Controlling the reduction potential you can selectively deposit nickel, leaving iron in the solution.

Note that you can't dissolve iron selectively, no matter what. Once you dissolve iron that is in contact with the solution you are left with a nickel on the surface and the solution has no access to the iron in the bulk of the electrode.

Okay, so I was correct to say that both go into solution but only Nickel is deposited at the cathode ?

[Ari Ben Canaan]

Please try and understand that I need closure on this matter 

[Borek]

Okay, so I was correct to say that both go into solution but only Nickel is deposited at the cathode ?

That would be the correct answer for me.

[Ari Ben Canaan]

Okay, so I was correct to say that both go into solution but only Nickel is deposited at the cathode ?

That would be the correct answer for me.

Thank you !!

+rep