Stoichiometry

Science

Definition

Stoichiometry is the area of chemistry that uses balanced chemical equations to calculate the quantitative relationships between reactants and products in a chemical reaction. It allows chemists to predict how much product will form or how much reactant is needed.

How It Works

  1. Write and balance the chemical equation.
  2. Convert given quantities (grams, liters, molecules) to moles using molar mass or Avogadro's number.
  3. Use mole ratios from the balanced equation to convert between substances.
  4. Convert moles of the desired substance back to the requested unit (grams, liters, etc.).
  5. Identify the limiting reagent if more than one reactant is given.

Examples

  • Calculating how many grams of CO₂ are produced from burning 10 g of methane
  • Determining the limiting reagent when mixing hydrogen and oxygen to make water
  • Finding the volume of gas produced at STP from a known mass of reactant
Key Fact

The mole ratio from the balanced equation is the key conversion factor in all stoichiometry problems

Related Terms

Mole concept Molar ratios Limiting reagents Balancing equations

Study This Concept

Practice stoichiometry with free review games in these units:

AP Chemistry Unit 4: Chemical Reactions