Stoichiometry and molecular composition

This course is a part of AP®︎ Chemistry, a 15-course Topic series from Khan Academy.

Learn about how to balance chemical equations, and how to use balanced chemical equations to do stoichiometry and molecular composition calculations.

This course contains 4 segments:

Balancing chemical equations

Stoichiometry

Now we are going to draw the connections between balancing equations and what happens in the lab (where you actually have a certain mass of a compound).

Limiting reagent stoichiometry

In a reaction, you often have extra of one molecule (or too little of the other) so all the reactant doesn't react. We'll explore how to identify which reactant is limiting which is helpful in a whole series of scenarios.

Molecular composition

We'll now explore two different ways of representing what elements are in a molecule: molecular and empirical formulas. Molecular formulas actually represent the number of atoms in a molecule while empirical formulas show us the ratio of the constituents based on experiments. In order to help us connect these ideas, we'll also explore a quantity called the "mole". Just as a "dozen" represents 12 of something, a "mole" represents roughly 602,200,000,000,000,000,000,000 of something. This will help us think about mass composition of molecules.