Question

What mass of gold is produced when 20.9 A of current are passed through a gold solution for 31.0 min ?

Answer 1

Gold is usually charged as Au+3

therefore

Au+3 and 3- --> Au(s)

1 mol of Gold ion, + 3 mol of electron --> 1 mol of Solid Gold

I = 20.9 A = 20.9 C/s

Total charge = t*I = 31mi*20.9 C/s = 31*60 s*20.9 C/s = 38874 C

F = 96500 C/mol

Therefore, mol of electrons:

mol e- = C/F = 38874/96500 =0.40283 mol of lectrons

we require 3 per mol of Au ion so

0.40283/3 = 0.13427 mol of Au+3 may be reduced

Therefore

MW = 196.96657 g/mol

mass = mol*MW = 0.13427*196.96657 = 26.446 g of Gold may be produced