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Limiting Reactant
If you have set quantities of two different reactants,
one will get used up and some amount of the
other will be leftover.
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Stoichiometry 3.5
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Limiting Reactant
ƒ The reactant that is used up limits how far the
reaction will proceed.
Excess Reactant
ƒ The reactant that is leftover when the reaction is
complete.
Step 1. Write a Balanced Chemical Equation
C6H12O6 + O2 Æ CO2 + H2O
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Step 1. Write a Balanced Chemical Equation
Ex1) (a) What is the limiting reactant when 28 g
of Glucose reacts with 14 g of Oxygen gas?
(b) What mass of CO2 is produced?
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Ex1) (a) What is the limiting reactant when 28 g
of Glucose reacts with 14 g of Oxygen gas?
(b) What mass of CO2 is produced?
Ex1) Limiting Reactant Problem
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Ex1) Limiting Reactant Problem
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Limiting Reactant
% Yield
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Ex1) Limiting Reactant Problem
Step 2. Find the mass of CO2 that would be
produced by each reactant.
C6H12O6 + 6 O2 Æ 6 CO2 + 6 H2O
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Ex1) (a) What is the limiting reactant when 28 g
of Glucose reacts with 14 g of Oxygen gas?
(b) What mass of CO2 is produced?
Ex1) Limiting Reactant Problem (cont.)
Step 1. Write a Balanced Chemical Equation
C6H12O6 + 6 O2 Æ 6 CO2 + 6 H2O
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Ex1) Limiting Reactant Problem (cont.)
Step 3. Compare the two masses produced.
The reactant that produced the smallest
quantity of product is the limiting reactant.
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Step 2. Find the mass of CO2 that would be
produced by each reactant.
C6H12O6 + 6 O2 Æ 6 CO2 + 6 H2O
Ex1) Limiting Reactant Problem (cont.)
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19 g < 41 g
(a) Thus, O2 is the limiting reactant.
(b) 19 g of CO2 is produced in theory.
Ex3) Limiting Reactant
Actual Yield
×100
Theoretical Yield
2 N2H4(l) + N2O4(l) Æ 3 N2(g) + 4 H2O(g)
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%Yield =
Ex3) (a) Find the limiting reactant 155 g of N2H4(l)
react with 175 g N2O4(l).
(b) What mass of H2O(g) is produced?
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Ex2) Find the percent yield if only 15 grams of
CO2 were produced in the previous problem.
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Ex2) Percent Yield
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Ex3) Limiting Reactant (cont.)
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Step 1. Find the mass of H2O that could be
produced by each reactant.
Step 1. Find the mass of H2O that could be
produced by each reactant.
2 N2H4(l) + N2O4(l) Æ 3 N2(g) + 4 H2O(g)
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2 N2H4(l) + N2O4(l) Æ 3 N2(g) + 4 H2O(g)
Ex3) Limiting Reactant (cont.)
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Ex3) Limiting Reactant (cont.)
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Ex2) Find the percent yield if only 129 grams of
H2O were produced in the previous problem.
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Step 3. Compare the two masses produced. The
reactant that produced the smallest quantity of
product is the limiting reactant.
Ex4) Percent Yield
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137 g < 174 g
(a) Thus, N2O4 is the limiting reactant.
(b) 137 g of H2O is produced in theory.
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