Curated OER
Limiting Reagents and Percent Yield Problems
Twelve questions about the various calculations of mass and yield are given here. There is significant practice of molarity calculations and consideration of the reactant and product balance.
Chem4kids
Chem4 Kids: Stoichiometry
This site provides a great overview of stoichiometry, the part of chemistry that studies amounts of substances that are involved in reactions. Content focuses on what you measure, and includes two examples.