1. Redox Reactions

2. Half Reaction One of the two parts of a redox reaction
Oxidation
Reduction
Includes element and electrons involved
Example: Fe  Fe e-

3. Example
Write the half reaction for when the element chlorine is converted into the chloride ion.

4. Example
Write the half reaction for when Fe2+ is converted to Fe4+ and state whether it is an oxidation or reduction.

5. Redox Reactions Oxidation and Reduction Reactions
Reaction in which electrons are transferred between atoms
Remember:
Oxidation is loss of electrons
Reduction is gain of electrons

6. In a chemical reaction, oxidation cannot happen without reduction
Pneumonic:
LEO the lion says GER.
Loss electrons is oxidation, gain of electrons is reduction

7. Oxidation and Reduction in Redox Reactions
Assign oxidation numbers to each element in all compounds and elements
Values that change tell you what substance is oxidized and what substance is reduced

8. Example
2 K + Br2  2 KBr
What is the charge of each element in the reaction?
What substance is reduced?
What substance is oxidized?

9. Example 3 SnCl4 + 2 Fe  3 SnCl2 + 2 FeCl3
What is the charge of each element in the reaction?
What substance is reduced?
What substance is oxidized?

10. Zn(s) + Cu2+ (aq)  Zn2+(aq) + Cu(s)
Example:
Write the two half reactions that make up this redox process and state which is oxidation and which is reduction:
Zn(s) + Cu2+ (aq)  Zn2+(aq) + Cu(s)

11. Balancing half reactions
Write each half reaction including the correct number of electrons gained or lost
While combining the two half reactions, make sure that the electrons cancel out
Example: Determine the balanced redox reaction between:
I2(s) +2e-  2I-(aq)
Fe(s) Fe2+(aq) + 2e-

12. Practice Problem
Determine the balanced redox reaction between: Co2+ (s) +2e-  Co(aq) Cr(s)  Cr3+(aq) + 3e-