1. Redox & Electrochemistry
Chapters 22 and 23

2. OXIDATION-REDUCTION REACTIONS (REDOX)
Nearly all chemical reactions involve the process of oxidation-reduction
Both reactions must occur simultaneously
Burning of fuel such as methane
Rusting, tarnishing, or corroding are all redox processes

3. Assigning oxidation numbers
In order to decide if a reaction is a redox reaction, you must assign oxidation numbers.

4. Rules for Assigning Oxidation Numbers
1. Oxidation state of monatomic ion= charge
Na+1 = _____ Fe+2=____
2. H = +1 in covalent compounds, and -1 in hydrides
HCl=_____ NaH=_________
3. Oxygen = 2 in compounds

5. Oxidation number of any uncombined element=0 K=_______ H2________
Sum of oxidation states = 0 in compounds
Sum of oxidation numbers= charge of ion
NO N=_______ SO4-2= S=_______

6. Oxidation Number Changes in Chemical reactions
Oxidation = loss of electrons
Reduction = gain of electrons
oil rig / leo says ger

8. Identifying REDOX reactions
To determine if a reaction is redox, keep track of oxidation numbers.
If the gain or loss of an electron can be shown, then reaction is redox
Double-replacement and acid /base reactions are NOT redox.
Color change may indicate redox

9. Using oxidation number changes to balance equations:
Assign oxidation numbers to all the atoms in the equation
Identify which atoms are oxidized and which are reduced
Write two half reactions to show the oxidation and reduction

10. Make the number of electrons gained = number of electrons lost by the use of a coefficient
Make sure that the equation is balanced for both charge and atoms.

11. Electrochemistry
The study of the interchange of chemical and electrical energy.

12. Galvanic or Voltaic Cell
A device in which chemical energy is changed to electrical energy.

13. Anode and Cathode OXIDATION occurs at the ANODE.
REDUCTION occurs at the CATHODE.
An ox saw a red cat.

14. Cell Potential
Cell Potential: The “pull” or driving force on the electrons.
Measured as E0

16. Batteries
A battery is a galvanic cell or, more commonly, a group of galvanic cells connected in series.