Question

Metallic copper can be made by the electrolysis of molten CuO. (a) What mass of Cu is formed by passing a current of 9.17 A through molten CuO for 2.50 days? The unbalanced chemical reaction representing this electrolysis is shown below. CuO Cu + O2 g of Cu is formed by this electrolysis. (b) How many minutes are needed to plate out 8.00 g of Cu from molten CuO using 7.18 A current? minutes are needed.

Answer 1

CuO = Cu+2 + O2-

Cu+2 + 2e- -->Cu(s)

so...

2 days = 24*2 = 48 hours = 48*3600 = 172800 seconds

so...

C = I*t = 9.17*172800 = 1584576 Coulumbds

mol of e- = 1584576 C / 96500 C/mol = 16.42 moles of e-

2 mol of e - ---> 1 mol of Cu+2

16.42 mol --> x

x = 16.42/2 = 8.21 mol of Cu

mass = mol*MW = 8.21*63.5 = 521.335 g of Copper

b)

minutes for 8 grams to form...

mol of copper = mass/MW = 8/63.5 = 0.1259 mol of Cu+2

so..

1 mol of Cu = 2 mol of e-

0.1259 mol of Cu = 0.1259*2 = 0.2518 mol of e-

total charge:

1mol of e- = 96500 C

0.2518 mol --> 0.2518*96500 = 24298.7 C

so..

I = C/t

t = C/I = 24298.7 / 7.18

t = 3384.220 seconds

t = 3384.220/60

t = 56.40 minutes