1. “minimal” galvanic cells
only need reactants Cu
Cu2+(aq) + 2e-  Cu(s)
o = 0.34 V
a) oxidation Zn
Zn2+(aq) + 2e-  Zn(s)
Zn  Zn2+ + 2e-
 = 0.76 V
o = V
b) oxidation H+
2H+(aq) + 2e-  H2(g)
o = 0.00 V
reduction
2H+ (aq)
+ Zn (s)
 Zn2+ (aq)
+ H2(g)
0 = .76 V
Q =
 =
very large

2. Electrolytic Cells galvanic cell electrolytic cell 2 H2(g) + O2(g) 
spontaneous
galvanic cell
cell < 0
G > 0
non-spontaneous
electrolytic cell
2 H2(g)
+ O2(g) 
2 H2O(l)
G = -474 kJ
spontaneous
redox reaction: H  1+ O  2-

3. Electrolytic Cells 2 H2O(l)  2 H2(g) + O2(g) G = 474 kJ
oxygen half-cell:
H2O
 O2 2
H2O  O2
+ 4 H+
+ 4 e-
a) oxidation
b) reduction
reaction
a) anode
b) cathode

4. Electrolytic Cells 2 H2O(l)  2 H2(g) + O2(g) G = 474 kJ
hydrogen half-cell:
H2O  H2 2
H2O
+ 2e-  H2
+ OH- 2
reduction reaction
cathode

5. Electrolytic Cells 2 H2O  O2 + 2 H2 2 H2O  O2 + 4 H+ + 4 e- anode
oxidation:
2 H2O  O2
+ 4 H+
+ 4 e-
anode
2( )
reduction:
2 H2O
+ 2e-  H2
+ 2 OH-
cathode
____________________________________
6 H2O
 O2
+ 2 H2
+ 4H+
+ 4 OH-
2 H2O  O2
+ 2 H2

6. Electrolysis of water - battery e- e- anode cathode oxidation+
battery e-
Pt electrodes e-
anode
cathode
oxidation
reduction
2H2O  O2+ 4H++ 4e-
4H2O + 4e- 2H2 + 4OH-
acid
base
1 mol gas
2 mol gas

7. Electrolysis of water 2.5 amp Power source  3.2 g O2 current =
amperes (A)
= coulombs/sec (C/s)
current
and time
charge
mol e-
mol
product
gram
product
A(C/s) x s
x 1mol e-
96,500 C
x mol product
mol e-
x g product
mol product

8. Electrolysis of water 2 H2O  O2 + 4 H+ + 4 e- 2.5 A, 3.2 g O2
current
and time
charge
mol e-
mol
product
gram
product
(C/s) x s
x mol e- C
x mol O2
mol e-
mol O2
x g O2
= g O2
1 mol e-
96500 C 1 4
2.5 A
32.0 g/mol
3.2

9. Electrolysis of water 2 H2O  O2 + 4 H+ + 4 e- 2.5 A, 3.2 g O2
1 mol O2 x
32 g O2
4 mol e- x
1 mol O2
96500 C =
1 mol e-
38600 C
3.2 g O2 x
2.5 C x s s
= C
s = s
15440 s x
1 min x
60 s
1 hr
60 min
= 4.3 hr

10. Electroplating Cu2+ + 2e-  Cu o = 0.34 V anode cathode Cu(s)
oxidation
reduction
Cu(s)
 Cu2+(aq)
+ 2e-
Cu2+(aq)
+ 2e-
 Cu(s)
Cu2+ + 2e-  Cu
o = 0.34 V

11. Electroplating anode cathode Cu(s)  Cu2+(aq) + 2e-
reduction
oxidation
Cu(s)  Cu2+(aq) + 2e-
Cu2+(aq) + 2e- Cu(s)
0.75 A
for 25 min.
deposits 0.37 g Cu
atomic mass of Cu =

12. Electroplating Cu2+(aq) + 2e- Cu(s)
0.75 A for 25 min deposits 0.37 g Cu
A (C) s
x s
x 1 mol e-
96500 C
x 1 mol Cu
2 mol e-
x g Cu
mol Cu

13. Electroplating 0.75(C) s x 25 min x 60s min = 1.125 x 103 C
x 1 mol e-
96500 C
= x 10-2 mol e-
1.17 x 10-2 mol e-
x 1mol Cu
2mol e-
=5.83 x 10-3mol Cu
0.37 g Cu
= g
mol
atomic mass Cu
5.8x10-3 mol Cu