How many minutes will it take to plate out 16.22 g of Al metal from a solution of Al3+ using a current of 14.6 amps in an electrolytic cell?

Question

How many minutes will it take to plate out 16.22 g of Al metal from a solution of Al³⁺ using a current of 14.6 amps in an electrolytic cell?

Answer 1

First, look at the reaction to decided how many moles of electrons it will take:

Al³⁺ + 3e- ==> Al(s)

It takes 3 moles of electrons to convert 1 mole of Al³⁺

Next, figure out how many moles of Al metal you want:

16.22 g Al x 1 mol Al / 26.98 g = 0.601 mols Al

And now how many moles of electrons that requires:

0.601 mols Al x 3 moles e- / mol Al = 1.80 moles of electrons

Now use the Faraday constant to find the number of coulombs (C) needed:

1.80 mols e- x 96485 C / mol e- = 174,016 C

Finally, knowing that 1 amp = 1 C/sec, we can use the 14.6 amps to find the time needed to supply 174,016 C:

174,016 C x 1 sec / 14.6 C = 11,919 sec

Converting this to minutes we have ... 11,919 sec x 1 min / 60 sec = 199 minutes (3 sig. figs.)