1. Electrochemistry
The study of chemical reactions that produce electrical current or are driven to occur by applying an electrical current.
galvanic cell
Chemical potential energy
Electrical potential energy
electrolytic cell
Where is the chemical potential energy stored?

2. Reactions In aqueous solution or molten salts (ionic reactions)
Heterogeneous – at electrode surfaces
Gases formation
Plating of metals/eroding (dissolving) metals

3. Solutions Homogeneous mixtures – variable composition Two components:
Solute
Solvent (usually water – aqueous solutions)
Molarity – unit of concentration
M = moles of solute/VL of solution
Moles = M x VL

4. Types of solutes
Non-electrolytes – do not dissociate, remain as molecules in solution (all molecules) such as sugars, alcohols
sugar (s)  sugar (aq)

5. Types of solutes continued
Electrolytes – dissociate in solution
Strong electrolytes -100% dissociation into ions – high conductivity (all ions)
NaCl (s)  Na+ (aq) Cl- (aq)
Weak electrolytes – partial dissociation into ions – poor/low conductivity (ions and molecules)
CH3COOH (aq) H+ (aq) + CH3COO- (aq)

6. Solubility “like dissolves like”
Ionic salts - Water
Molecular compounds – non-aqueous solvents
Usually solubility increases with increasing temperature
Solubility rules

7. A measure of acidity: pH
H H OH-
Kw = (H+)(OH-) = 1.0 x at 25oC
Define: pH = -log (H+)
In general pX = -logX
pOH = -log (OH-)
pH scale: acidic (H+) > (OH-) pH < 7
neutral (H+) = (OH-) pH = 7
basic (H+) < (OH-) pH > 7

8. Types of conduction - movement of charged particles
Metallic conduction - electrons in metals
ionic or electrolytic conduction - ions in molten salts or aqueous solutions
gaseous conduction - ions and electrons in the gas phase (atomic plasmas) Geiger-Muller Tube for radioactive decay particles

9. Redox Processes - electron transfer
oxidation -
loss of electrons
oxidation number increases
Ag  Ag+ + e-
reduction -
gain in electrons
decrease in oxidation number
Fe e-  Fe

10. Consider silver plating a copper penny
Redox Reactions
Both oxidation and reduction MUST occur in the reaction and the number of electrons exchanged MUST be balanced
Consider silver plating a copper penny
Cu Ag+  Cu Ag 2 2
Cu  Cu e-
What is being oxidized?
What is being reduced?
Ag+ + e-  Ag
x 2
MUST balance number of electrons exchanged