1. Oxidation Number Practice
MgCl2
Mg(NO3)2
Al2(SO4)3
Ba(NO3)2
FeCl3
OF2
H2O2
Al2S3 Fe O2
Work from outside in, start with O or F if possible
More examples:
FePO4
P2O5
N2O4
CO2

2. Redox Equations
Identify what is being oxidized and what is being reduced (LEO goes GER)
Reducing agent – causes reduction (is oxidized)
Oxidizing agent – causes oxidation (is reduced)
Draw arrows from element in reactants to products, write the charge and determine if it has gained or lost electrons

4. Redox Example 1 CH4 + 2O2 → CO2 + 2H2O Write in ox numbers and arrows
C-4 is oxidized
O20 is reduced

5. Redox Example 2 Cr2O72- + OH- → 2CrO42- + H2O
Not redox because ox numbers don't change

6. Redox Example 3 2H2O2 → 2H2O + O2 H2O2 is ox agent and reducing agent
O from peroxide is reduced to O in water and oxidized to O in O2

7. Redox Practice

8. Activity Series
Used to determine the products of a single replacement reaction
An element higher in the series will replace a lower element in a compound
Zn(s) + CuCl2(aq) → ZnCl2(aq) + Cu
Determine what is oxidized and what is reduced
What conclusion can you make about oxidation and replacement?
Higher the element, the easier it will be oxidized

13. Writing Half Reactions
CH4 + 2O2 → CO2 + 2H2O
oxidation: CH4 → CO2
reduction: 2O2 → 2H2O
Zn + 2HCl → ZnCl2 + H2
ox: Zn → Zn+2 + 2e-
red: 2e- + 2H+ → H2
overall: Zn + 2H+ → Zn+2 + H2

14. Balancing Redox by Half Reaction Method
1. write half reaction for oxidation reduction
Do not include polyatomic ions that do not change
2. For each half reaction:
Balance all elements except H and O
Balance O by adding H2O
Balance H by adding H+
Balance charge using electrons
3 if necessary, multiply one or both of the balanced half reactions to equalize the number of electrons in the 2 half reactions
4. add half reactions – cancel identical species on opposite sides of the arrow
5. check elements and charges are balanced