[L3ul]

What quantity of nickel would we obtain by the electrolysis of an acid solution of NiCl₂, if:
the electrolysis time is 30min; the electrolysis potential is 2.5V; the polarization potential is 2V; the cell's resistance is 0.5Ω; and the current efficiency is 75%.

As far as I know, the potential required for the electrolysis process to take place (also called the decomposition potential or electrolysis potential - E_d) is:
[tex]E_{d}=-E+E_{p}+R \cdot I[/tex]
E - the cell's potential
E_p - the polarization potential or the overpotential
By looking into a standard reduction potentials table for Ni²⁺/Ni and O₂/H₂O, I find that E=-1.48V.
Therefore:
[tex]R \cdot I=E_{d}+E-E_{p}=2.5-1.48-2=-0.98 [/tex] (which looks... wrong)
What am I doing wrong?

[Borek]

O₂/H₂O depends on pH, which is not given.

Nomenclature used is not clear to me (English is not my first language). My bet is that you are expected to simply find the current from the potential and resistance.

[L3ul]

Neither is mine - this is a translation from a Romanian textbook.

Here's is the solution they gave to me; I do not understand it since it does not include the cell's potential:

[tex]E_e = E_p + R\cdot I [/tex]
[tex]I=\frac{E_e - E_p}{R}, m_{Ni}=0.684g[/tex]

[mjc123]

I don't see how they get that result, with the numbers given, except on the assumption that there are 100 s in 1 min. Then it works!

[L3ul]

Indeed, you get a different numerical value using their numbers along with their formulas.
Also, nice work on finding their mistake!

But because of this observation, I must make a note here: on another problem, they use the same formula for the current's intensity and, with the numbers given, you get their result.
Maybe they consider the polarization potential (E_p) as the potential require to overcome the cell's potential and the overpotential. But I've never heard of such a value...
Am I making the right assumption consider that this is what they mean when they say polarization potential?