A video demonstration of The Mole and Avogadro's Number from Salman Khan of Khan Academy.
Khan Academy

Brief explanations of terms and formula plus variations of the formula
AusETute

How to form dilutions of solutions.
Mountain Empire Community College dilutions page

Describes how to calculate the weight percent of a solute in solution. Provides worked examples and practice problems with answers.
Weight Percent

How to calculate the volume percent of a solute in a solution.
Volume Percent

How to calculate normality, specifically how it may differ from molarity.
Normality

How to find the concentration of a chemical species (ions) in a solution.
Species Concentration

How to solve dilution problems using molarity of solutions. Practice problems with answers are included.
Dilution Calculations

In this video, Dr. Harold Goldwhite gives an introduction to Empirical and Molecular Formulas.
Educator.com

