[BaO]

In the electro-refining of an ore, the ore is dissolved and the solution placed in an electrolytic cell. A specific ore produces a solution which contains Na+ , Cu2+ , Pb2+ and Ag+ . Which of these metals can be plated out from the solution by electrolysis?

A. all four metals
B. Cu and Pb only
C. Na, Cu and Pb only
D. Cu, Pb and Ag only

could you help me out of this question?
is water involved in this case?
   

[Borek]

is water involved in this case?

Yes. It will decompose before one of the metals will be deposited.

[BaO]

so compare H2O and those ions to see which one will have more tendency to reduce ,right?
because i think "to be plated out" is to be reduced , is it correct?

[Borek]

Right & right.

Although in the first case it is more tendency of H⁺ to be reduced then tendency of the water to be reduced - note that due to autodissociation H⁺ are always present in water solutions.

[BaO]

what is an ore anyway? is it Tin or something?
i'm still wondering that why we have to compare those ions to H2O ? why not something else?

[Borek]

what is an ore anyway? is it Tin or something?

Ore is an ore, check in dictionary.

i'm still wondering that why we have to compare those ions to H2O ? why not something else?

Because they are dissolved in water, not in something else.