Question

How long will it take to plate out each of the following with a current of 100.0 A?

a. 1.0 kg `Al` from aqueous `Al^(3+)`
b. 1.0 g `Ni` from aqueous `Ni^(2+)`
c. 5.0 mol `Ag` from aqueous `Ag^+`?

Answer 1

The key here is translating the electrons required into faradays. Moreover,

`1A = (1C)/s`

This is basically a long unit conversion problem, I will do each in turn, below,

`1.0kg * (10^3g)/(kg) * ("mol")/(27.0g) * (3"mol"e^-)/("mol") * (96485"C")/("mol"e^-) * s/(100.0"C") approx 30"hr"`

I've omitted the time conversions above for brevity's sake, and will do so if the `"s"` answer is unreasonably high subsequently. Basically `1"hr" = 60min = 60"s"`.

`1.0g * ("mol")/(58.7g) * (1"mol"e^-)/("mol") * (96485"C")/("mol"e^-) * (s)/(100.0"C") approx 16"s"`

`5.0"mol" * (1"mol"e^-)/("mol") * (96485"C")/("mol"e^-) * (s)/(100.0"C") approx 1.3*10^4"hr"`

These are pretty common on exams, I would familiarize yourself with them and practice some more given the models I've supplied above.