Not sure how to attempt this question?

[Hermione11]

A 0.5M nickel sulfate solution was electrolysed for five minutes.
If the experiment was repeated, which of the following changes would cause the largest increase in the amount of nickel deposited?

A. Increasing the time for the electrolysis by one minute.
B. Increasing the concentration of the solution to 0.6M.
C. Increasing the surface area of the electrodes used by twenty percent.
D. Increasing the temperature of the solution from 20˚C to 25˚C.

Thanks in advance!

[kenhung123]

I think it is D based on the idea that increasing temperature increases the rate (assuming the reaction is not complete in the initial reaction) and it also increases the amount of reactants capable of undergoing the reaction (over the activational energy barrier)

[Hermione11]

But you haven't rule out any of the other ones though?

[Nobby]

I'd say it's A, as that's going to increase the amount of electrons available to reduce Ni²⁺ to Ni metal.

[Hermione11]

Yes but you have to rule out the others
I think more than one of them will increase the amount of Ni deposited, so just saying A is a huge guess when possibly one of the others could also increase the amount of Ni
The question is which would cause the largest increase?

[thushan]

OK, so we need to see what would increase the mass of nickel deposited. Assuming all the electrons are collected by Ni2+, the two things that would do it are TIME and CURRENT.

B won't do anything, it just increases the amount of Ni2+ available, but will not change either TIME or CURRENT.
C might decrease the resistance of the solution (assuming the potential difference across the solution is the same), but I think this would be negligible, so TIME doesn't change, but CURRENT might increase slightly.
D - I'm not sure as to how resistance of solution changes with temperature, I think the effect (from 20 to 25 degrees) will be negligible.

With A though, the TIME is being increased. I'd go with A.

[Hermione11]

Thank you!

[thushan]

No worries