Question

Calculate how many grams of gold would be plated out on a coin, if a current of 3.1 (Amp) is applied for 13 min to an electrolytic cell shown above. The following reaction is occurring:

Au3+ + 3 e- → Au

MW for gold equals 197g / mol. 1 amp (A) = 1 coulomb/second (C/s) Charge on 1 mol of electrons = 96500 coulombs (C) = 1 faraday (F) Calculate the number of grams plated out. You must take into consideration the number of moles of electrons necessary to reduce each gold ion to gold.

Answer 1

the electrolysis expression is:

Au3+ + 3e- ------> Au

1 mol of Au requires 3 mol of electron

1 mol of electron = 96485 C

So,1 mol of Au requires 289455 C

let us calculate the charge passed:

t = 13.0 min = 13.0*60 s = 780 s

time, t = 780s

Q = I*t

= 3.1A * 780s

= 2418 C

mol of Au plated = 2418/289455 = 0.00835 mol

Molar mass of Au = 197 g/mol

mass of Au = number of mol * molar mass

= 0.00835 * 197

= 1.65 g

Answer = 1.65 g