Electroplating -How long does it take?

Question

Consider the electrolysis of molten AlCl3 to obtain pure Aluminum metal using 15 Ampere current. How many hours would it take to produce 35 kg of Aluminum metal? (1Faraday=96485 Coulombs)

Answer 1

Al³⁺ + 3e- ==> Al(s)

moles Al(s) = 35 kg Al x 1000 g/kg x 1 mol/26.98 g = 1297 moles Al

moles electrons = 1297 moles Al x 3 moles e-/mole Al = 3891 moles electrons

Coulombs = 3891 moles e- x 96,500 C/mole = 3.76x10⁸ C

Recall that 1 amp = 1C/sec therefore 15 amps = 15 C/sec

3.76x10⁸C x 1 sec/15 C = 2.5x10⁷ sec

Converting to hours...

2.5x10⁷ sec x 1 min/60 sec x 1 hr/60 min = 6.9x103 hours = 6900hours

(NOTE: I used 96.500 C/F instead of 96.485 as I didn't notice it in your question. Also, I rounded off which you may not want to do).