Lab #7: Limiting
Reagent
CHEM 105 - Lab 01 - Spring 2026
Instructor: Rachel Mathews
Why do
reactions stop?
Reactions proceed until one reactant is used up; the other
reactants are then in excess.
The limiting reactant is the substance that is completely consumed in a
chemical reaction; it determines the amount of product formed.
The non-limiting reactant (Excess reagent) is that which is not used up
completely during the reaction.
How do we determine the limiting reactant?
1. Write a balanced chemical equation
2. Calculate the moles of each reactant
3. Calculate the moles of the product for each reactant
4. Compare the moles of the product: The reactant that produces the
smallest amount of the product is the limiting reactant
How to Determine the
Limiting Reactant
Safety Precautions
Heating Substances
Wear safety glasses and gloves when boiling water
Keep your face away from beakers
Never leave the hotplate unattended
Use safety tongs and heat-resistant gloves
Turn hot plate off after use