1. Oxidation Reduction

2. Oxidation and reduction
REDOX
Where reactants exchange electrons -
Examples:
All types of batteries
alkaline, NiCad, car batteries
Rusting and corrosion
Metabolism
Antioxidants (Vit C, E prevent oxidation) 13

3. Oxidation and reduction
REDOX
Where reactants exchange electrons -
Oxidation = Losing electrons
LEO: Lose Electrons Oxidation
(Gain O or Lose H)
Reduction = Gaining electrons
GER: Gain Electrons Reduction
(Gain H or Lose O)
LEO the lion says GER

4. Oxidation and reduction
(Get reduced)
Chapter 18, Figure 18.19
(Get oxidized)

5. Oxidation and reduction
LEO 4+ 3+ 2+ 1+ 1- 2- 3- 4-
Chapter 18, Figure 18.20
GER

6. Oxidation and reduction
Assign Oxidation States:
2 Na(s) + Cl2 (g)  2 NaCl 1+ 1-
For element in natural form
Ox State = 0.
For simple ions,
Ox state = charge.

7. Oxidation and reduction
Who’s loosing or gaining electrons?
Loses
1 e- = LEO
2 Na(s) + Cl2 (g)  NaCl
Gains
1 e-=GER 1+ 1-
Na loses e- (LEO) Na gets oxidized
Cl gains e- (GER) Cl gets reduced

8. Oxidation and reduction
Oxidation - when a reactant loses e-(s). (LEO)
Na (s) Na+ + e-
Reduction - when a reactant gains e-(s). (GER)
Cl2 (g) + 2 e Cl-
These are half reactions 14

9. Oxidation and reduction
Who’s loosing or gaining electrons?
Loses
1 e- =LEO
2 Na(s) + Cl2 (g)  NaCl
Gains
1 e- =GER 1+ 1-
Na loses e- (LEO) so Na gets oxidized
Na caused Cl to get reduced
Na is the Reducing agent

10. Oxidation and reduction
Who’s loosing or gaining electrons?
Loses
1 e- =LEO
2 Na(s) + Cl2 (g)  NaCl
Gains
1 e- =GER 1+ 1-
Cl gains e- (GER) so Cl gets reduced
Cl caused Na to get oxidized
Cl is the Oxidizing agent

11. REDOX reactions 4 Fe + 3O2 2 Fe2O3 Lose 1 e- = LEO 3+ Gain 2-3+
4 Fe + 3O Fe2O3
Gain
1 e- = GER 2-
Iron is oxidized and is a reducing agent.
Oxygen is reduced and is an oxidizing agent. 17

12. REDOX reactions 2 H2 + O2 2 H2O Lose 1 e- = LEO 1+ Gain 2- 1 e- = GER1+
2 H2 + O H2O
Gain
1 e- = GER 2-
Hydrogen is oxidized and is a reducing agent.
Oxygen is reduced and is an oxidizing agent. 17

13. Oxidation and reduction
Chapter 18, Figure 18.19

14. Acid Reactions ZnCl2 + H2 Lose 1 e- = LEO Zn + HCl  Metal Acid Salt1+ 1- 2+ 1-
Gain
1 e- = GER H+
Cl- Zn
Ie. Hollow pennies

15. Element give e’s to ion lower on list
Activity series of metals
potassium
calcium
magnesium
aluminum
zinc
chromium
iron
nickel
tin
lead
copper
silver
platinum
gold
Hydrogen
Zn + Cu+1  Zn+2 + Cu
increasing reactivity
Element give e’s to ion lower on list

16. Zn + Cu+1  Zn+2 + Cu Voltaic Cell Cu+1 + e- Cu Zn  Zn+2 + 2e- LEO
Lose
1 e- = LEO
Zn + Cu+1  Zn+2 + Cu
Gain
1 e- = GER
Zn  Zn+2 + 2e-
Cu+1 + e- Cu
LEO
Oxidation at Anode
GER
Reduction at Cathode

17. Voltaic Cell

18. Voltaic Cell Zn + Cu+1  Zn+2 + Cu increasing reactivity potassium
calcium
magnesium
aluminum
zinc
chromium
iron
nickel
tin
lead
copper
silver
platinum
gold
Hydrogen
-2.92 eV
-2.87
-2.37
-1.67
-0.76
-0.74
-0.44
-0.24
-0.14
-0.13
+0.34
+0.80
+1.20
+1.50
0.00
Zn + Cu+1  Zn+2 + Cu
0.76
0.34
1.10 volts
increasing reactivity

19. Zn + NH4+1  Zn+2 + NH3 Dry Cell Battery NH4+1 + e- NH3+ H2
Lose
1 e- = LEO
Zn + NH4+1  Zn+2 + NH3
Gain
1 e- = GER
Zn  Zn+2 + 2e-
NH4+1 + e- NH3+ H2

20. Element give e’s to ion lower on list
Activity series of metals
potassium
sodium
calcium
magnesium
aluminum
zinc
chromium
iron
nickel
tin
lead
copper
silver
platinum
gold
Hydrogen
Al + Fe+3  Fe + Al+3
Black Iron coats inside of Al pan
increasing reactivity
Fe + H+  Fe+3 + H2
Acidic food turns Iron into soluble ions
Element give e’s to ion lower on list

21. Electroplating
Cr+2 + 2e- Cr

22. Hydrogen-Oxygen Fuel Cell
2H2 + 4OH1-  4H2O + 4e-
O2 + 2H2O + 4e- 4OH1-
Oxidation at Anode
Reduction at Cathode

23. Hydrogen-Oxygen Fuel Cell

24. Combustion The Ultimate Oxidation CH4 + 2O2  CO2 + 2H2O LEO 4- 1+ 4+4+ 2- 1+ 2-
GER
Carbon is oxidized and is a reducing agent.
Oxygen is reduced and is an oxidizing agent.