Question

How many minutes will it take to plate out 4.50 g of Cu from a solution of Cu(NO3)2 (aq) onto the cathode of an electrolytic cell when 8.00 A of current are used?

	28.5 min
	3.06 × 10−9 min
	14.2 min
	1.82 × 103 min

Answer 1

Electrolysis equation is:

Cu2+ + 2e- ------> Cu

1 mol of Cu requires 2 mol of electron

1 mol of electron = 96485 C

So,1 mol of Cu requires 192970 C

let us calculate mol of element deposited:

molar mass of Cu = 63.55 g/mol

use:

number of mol of Cu, n = mass of Cu/molar mass of Cu

= 4.5/63.55

= 7.081*10^-2 mol

total charge = mol of element deposited * charge required for 1 mol

= 7.081*10^-2*1.93*10^5

= 1.366*10^4 C

use:

time = Q/i

= 1.366*10^4/8

= 1.708*10^3 seconds

= 1.708*10^3/60 min

= 28.5 min

Answer: 28.5 min