1. Limiting Reactant

2. Identify the limiting reactant and calculate the mass of a product, given the reaction equation and reactant data.
Include: theoretical yield, experimental yield
Additional KEY Terms
Excess reactant

3. How many BLT Sandwiches can you make with 3 Tomatoes, 2 Kg of Bacon, 1 head of lettuce and 4 slices of bread? 2

4. Limiting Reactant - determines the amount of product that can be formed in a reaction.
N2 (g) H2 (g)
2 NH3 (g)
2 moles moles N H H N H N N H H
Reactants remaining are called the excess reactants.

5. Limiting Reactant Problems
Step 1: Record what you HAVE
Step 2: Calculate what you NEED
Pick one reactant and calculate how much of the other you will need.
Step 3: Determine the limiting reactant and excess reactant
Step 4: Use limiting reactant to determine the amount of product.

6. Pick one reactant and calculate the other
How much NaCl is produced and what is left over when 6.70 mol of Na react with 3.20 mol of Cl2?
6.70 mol
3.20 mol
2 Na (s) + Cl2 (g) NaCl (s)
HAVE
NEED
Pick one reactant and calculate the other
6.70 mol Na
1 mol Cl2 =
3.35 mol
Cl2 (need)
2 mol Na

7. 2 Na (s) + Cl2 (g) 2 NaCl (s) = 6.40 mol Na (need) 3.20 mol Cl2
HAVE mol mol
NEED mol
Pick one reactant and calculate the other
3.20 mol Cl2
2 mol Na =
6.40 mol
Na (need)
1 mol Cl2
Both calculations lead to the same conclusion:
Cl2 - limiting reactant Na - excess reactant

8. Cl2 - limiting reactant Na - excess reactant
2 Na (s) + Cl2 (g) NaCl (s)
HAVE mol mol
NEED mol mol
Cl2 - limiting reactant Na - excess reactant
3.20 mol Cl2
2 mol NaCl
= mol NaCl
1 mol Cl2
You could use your data to calculate exactly how much excess is left over:
6.70 mol mol = 0.30 mol Na excess

9. N2 (g) + 3 H2 (g) 2 NH3 (g) = 16.3 g N2 = 3.90 g H2
How many grams of ammonia can be made from 3.50 g of H2 gas and 18.0 g of nitrogen gas? What’s left?
N2 (g) H2 (g) NH3 (g)
HAVE g g
NEED
16.3 g
3.90 g
3.50 g H2
1 mol H2
1 mol N2
28.0 g N2
= g N2
2.0 g H2
3 mol H2
1 mole N2
18.0 g N2
1 mol N2
3 mol H2
2.02 g H2
= g H2
28.0 g N2
1 mol N2
1 mole H2

10. H2 - limiting reactant N2 - excess reactant
N2 (g) H2 (g) NH3 (g)
HAVE g g
NEED
16.3 g
3.90 g
H2 - limiting reactant N2 - excess reactant
3.50 g H2
1 mol H2
2 mol NH3
17.0 g NH3
2.0 g H2
3 mol H2
1 mol NH3
= g NH3
18.0 g – 16.3 g = 1.70g N2 left

11. 5 3 4 C3H8 (g) + O2 (g) CO2 (g) + H2O (g)
What volume of carbon dioxide is formed by the reaction of 75.0 g of propane and L of oxygen at STP?
C3H8 (g) O2 (g) CO2 (g) + H2O (g) 5 3 4
HAVE g L
NEED
58.9 g
191 L
75 g C3H8
1 mol C3H8
5 mol O2
22.4 L O2
= 191 L O2
44 g C3H8
1 mol C3H8
1 mol O2
150 L O2
1 mol O2
1 mol C3H8
44 g C3H8
= 58.9 g C3H8
22.4 L O2
5 mol O2
1 mol C3H8

12. O2 - limiting reactant C3H8 - excess reactant
C3H O CO H2O
HAVE g L
NEED
58.9 g
191 L
O2 - limiting reactant C3H8 - excess reactant
150 L O2
1 mol O2
3 mol CO2
22.4 L CO2
= 90 L CO2
22.4 L O2
5 mol O2
1 mol CO2
75.0 g – 58.9 g = 16.1 g C3H8 left

13. The limiting reactant is completely consumed.
The excess reactant is NOT used up.
When solving limiting reactant problems:
Balance the chemical equation first
Find the limiting reactant
Use limiting reactant to determine the product
Calculate the excess

14. CAN YOU / HAVE YOU?
Identify the limiting reactant and calculate the mass of a product, given the reaction equation and reactant data.
Include: theoretical yield, experimental yield
Additional KEY Terms
Excess reactant