20.1: Electrochemistry

ELECTROCHEMISTRY

Oxidation Numbers: Assign and determine if a reaction is going under oxidation or reduction

   a) Oxidation / Reducing Agent: Loses electrons

   b) Reduction / Oxidizing Agent: Gains electrons

Rules:

1. Pure, most stable form = 0

2. Ion in solution (Pb+2) = Charge of the ion

3. For the most part: Oxygen = -2, Fluorine = -1, Hydrogen = +1

Example:

 

Oxidation: Reducing Agent: Cd (0 --> +2)
Reduction: Oxidizing Agent: NiO2 (+4 --> +2)

Balancing Redox Reactions in Acidic Solutions

1. Separate into oxidation / reduction reactions.

2. Balance elements other than O, H

3. Balance O by adding H2O

4. Balance H by adding H+
    a)For Basic solutions only!: add OH to both reactant and product sides.

5. Balance charge by adding electrons

6. Equate electrons in both equations (multiply by coefficients)

7. Add back together the equations.

Example (1):

Balance the following equation in ACIDIC SOLUTION:

Example (2):
Balance the following equation in BASIC SOLUTION: