1. Chapter 9 Chemical Quantities in Reactions
9.3 Limiting Reactants
Learning Goal Identify a limiting reactant when given the quantities of two reactants; calculate the amount of product formed from the limiting reactant.
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2. A limiting reactant in a chemical reaction is the substance that
Limiting Reactants
A limiting reactant in a chemical reaction is the substance that
runs out first
stops the reaction
limits the amount of product that can form
© 2014 Pearson Education, Inc.

3. Limiting Reactants
A table setting consists of one fork, one knife, and one spoon.
How many table settings are possible from 6 forks, 4 spoons, and 7 knives?
What is the limiting item?

4. Four table settings are possible.
Limiting Reactants
Four table settings are possible.
The limiting item is the spoon.
Initial
Used
Extra
forks 6 4 2
spoons
knives 7 3

5. Limiting Reactants
How many peanut butter sandwiches can be made from 8 slices of bread and 1 jar of peanut butter?
With 8 slices of bread, only 4 sandwiches can be made. The bread is the limiting reactant.

6. Limiting Reactants
How many peanut butter sandwiches can be made from 8 slices of bread and 1 tablespoon of peanut butter?
With 1 tablespoon of peanut butter, only 1 sandwich can be made. The peanut butter is now the limiting reactant.

7. Guide to Calculating Moles of Product from a Limiting Reactant

8. Moles of Product from a Limiting Reactant
When 4.00 moles of H2 and 2.00 moles of Cl2 are mixed, how many moles of HCl form? What is the limiting reactant?
H2(g) Cl2(g)  2HCl (g)
4.00 mol mol ? mol
Step 1 State the given and needed moles.
Given: moles of H2
2.00 moles of Cl2
Need: moles of HCl, limiting reactant

9. Moles of Product from Limiting Reactant
H2(g) Cl2(g)  2HCl (g)
4.00 mol mol ? mol
Step 2 Write a plan to convert the given to the needed moles.
moles of H2
moles of
HCl
moles of
Cl2
moles of
HCl
Mole–Mole factor
Mole–Mole factor

10. H2(g) + Cl2(g)  2HCl (g) Moles of Product from Limiting Reactant
4.00 mol mol ? mol
Step 3 Use coefficients to write mole−mole factors from the equation.
1 mole of H2 = 2 moles of HCl

11. H2(g) + Cl2(g)  2HCl (g) Moles of Product from Limiting Reactant
4.00 mol mol ? mol
Step 3 Use coefficients to write mole−mole factors from the equation.
1 mole of Cl2 = 2 moles of HCl

12. Moles of Product from Limiting Reactant
H2(g) Cl2(g)  2HCl (g)
Step 4 Calculate the moles of product from each reactant, select the smaller number of moles as the amount of product formed from the limiting reactant.
HCl from H2:
HCl from Cl2:
Limiting reactant

13. Mass of Product from Limiting Reactant

14. Mass of Product from Limiting Reactant
In a catalytic converter, nitrogen monoxide reacts with carbon monoxide to form carbon dioxide and nitrogen gas. If 16.0 g of NO reacts with 12.0 g of CO, how many grams of CO2 can be produced?
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
Step 1 State the given and needed quantities (grams).
Given: g of NO, 12.0 g of CO
Need: grams of CO2

15. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? grams
Step 2 Write a plan to convert the grams of each reactant to grams of product.
Molar Mass
Mole–Mole factor
Molar Mass
grams
of NO
moles
of NO
moles
of CO2
grams
of CO2
Molar Mass
Mole–Mole factor
Molar Mass
grams
of CO
moles
of CO
moles
of CO2
grams
of CO2

16. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of NO = g of NO

17. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of CO = g of CO

18. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of CO2 = g of CO2

19. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
2 moles of NO = 2 moles of CO2

20. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? Grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
2 moles of NO = 2 moles of CO2

21. Mass of Product from Limiting Reactant
2NO(g) + 2CO(g)  2CO2(g) + N2(g)
16.0 g g ? grams
Step 4 Calculate the grams of product from each reactant and select the smaller number of grams of product.

22. Learning Check
Calculate the mass of water produced when
8.00 g of H2 and 24.0 g of O2 react.
2H2(g) + O2(g)  2H2O(l)

23. Solution
Calculate the mass of water produced when 8.00 g of H2 and 24.0 g of O2 react.
2H2(g) + O2(g)  2H2O(l)
Step 1 State the given and needed quantities (grams). Given: g of H2, 24.0 g of O2
Need: grams of H2O

24. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 2 Write a plan to convert the grams of each reactant to grams of product.
Molar Mass
Mole–Mole factor
Molar Mass
grams
of H2
moles
of H2
moles
of H2O
grams
of H2O
Molar Mass
Mole–Mole factor
Molar Mass
grams
of O2
moles
of O2
moles
of H2O
grams
of H2O

25. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of H2 = 2.02 g of H2

26. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of O2 = g of O2

27. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of H2O = g of H2O

28. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
2 moles of H2 = 2 moles of H2O

29. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 3 Use coefficients to write mole−mole factors; write molar mass factors.
1 mole of O2 = 2 moles of H2O

30. Solution 2H2(g) + O2(g)  2H2O(l)
8.00 g g ? grams
Step 4 Calculate the grams of product from each reactant and select the smaller number of grams of product.