1. Limiting reactant

2. Limiting Reactant Limiting Reagent
The reactant that is totally used up during the chemical reaction
Limits the amount of product produced

3. Excess Reactant Excess Reagent
The reactant present in a quantity that is greater than what is needed to react with the limiting reactant
Remains after the limiting reactant has been used up

4. Graham crackers
Marshmallows
Chocolate rectangle #1
Item Count 6 2 3 #2
Projected # of S’mores 1 #3
Left over
1. Why don’t all of your projected # of S’mores in line #2 match the actual number of S’mores you can make?
2. What limited the total number of S’mores you can make?
3. What is another word for left over?

5. Steps
Use stoichiometry to convert any reactants given into the specified product (if no product specified choose one)
Identify limiting reactant (LR), excess reactant (ER), and max amount of product
To calculate how much in excess, subtract the max amount of product and use stoichiometry to convert back to grams of reactant

6. Example 1 1 MgBr2 + 2 AgNO3 2 AgBr + 1 Mg(NO3)2
How many grams of silver bromide can be formed when solutions containing 50.0 g of magnesium bromide and g of silver nitrate are mixed together? What is the limiting reactant? What is in excess?
1 MgBr AgNO AgBr + 1 Mg(NO3)2
50.0 g MgBr2 1 mol MgBr mol AgBr g AgBr
g MgBr mol MgBr mol AgBr
= 102 g AgBr
100.0 g AgNO3 1 mol AgNO mol AgBr g AgBr
g AgNO mol AgNO mol AgBr
= g AgBr
Limiting Reactant (LR) = MgBr2
Excess Reactant (ER) = AgNO3

7. Example 2
How many grams of hydrogen chloride can be produced from 1.00 g of hydrogen and 55.0 g of chlorine? What is the limiting reactant? What is in excess?
H2 + Cl HCl
1.00 g H mol H mol HCl g HCl
2.02 g H mol H mol HCl
= 36.1 g HCl
55.0 g Cl mol Cl mol HCl g HCl
70.90 g Cl mol Cl mol HCl
= 56.6 g HCl
Limiting Reactant (LR) = H2
Excess Reactant (ER) = Cl2

8. Example 3
How many grams of barium sulfate will be formed from g of barium nitrate and g of sodium sulfate? What is the limiting reactant? What is in excess?
Ba(NO3)2 + Na2SO BaSO4 + 2 NaNO3
200.0 g Ba(NO3)2 1 mol Ba(NO3) mol BaSO g BaSO4
g Ba(NO3)2 1 mol Ba(NO3)2 1 mol BaSO4
= g BaSO4
150.0 g Na2SO4 1 mol Na2SO mol BaSO g BaSO4
g Na2SO mol Na2SO mol BaSO4
= g BaSO4
Limiting Reactant (LR) = Ba(NO3)2
Excess Reactant (ER) = Na2SO4