Name ___________________________________ Date ______________________ Class ______________________
Chapter 12 – Stoichiometry
Limiting Reactants Virtual Lab
Directions to access the virtual lab website:
You will be visiting the website www.sascurriculumpathways.com. You can Google this website or you can type it in and
end up in the correct place. Once you are there, in the upper right hand corner of the page is a place for a QL#. Our QL#
for today is 10. You will be asked for a username and a password. The username is language33seeds. If you use this
username you do not need a password.
About the Topic:
Imagine that you are an assembly-line worker at the local widget factory.
Each widget requires the following parts:
Your supply bin contains the following parts:
How many widgets can you make?
Will any of the parts be used up completely? If so, which one(s)?
Which parts and how many of each will be left over?
Why couldn’t you make more widgets from the left over parts?
Widget making is governed by the same rules as chemical reactions. Consider the following reaction:
12HClO4 + P4O10 → 4H3PO4 + 6Cl2O7
Suppose that 10.0 grams HClO4 were to react with 10.0 grams P4O10. What mass of each product would form? As in
the widget factory, one part (reactant) might be used completely, but an excess might remain for the other part
(reactant). The availability of parts will affect the number of widgets that can be produced or, in a chemical reaction, the
product masses that can form.
About the Simulation:
A. RESET: removes reactants and products from the pans on the scales
and clears all displays.
B. REACTANT VALUES:
 Provide information for each reactant, including.
 State (solid, gas, liquid/aqueous)
 Chemical formula
 Quantity in grams, moles, or particles
 Allow you to change a reactant quantity by typing in a new value (all
other quantities will update.
 All you to select unit of measure (grams, moles, or particles).
Adapted from: http://www.sascurriculumpathways.com/portal/
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C. REACTANT COMBINATIONS: lets you choose the reaction you want to investigate.
D. PRODUCT VALUES:
 Provide information for each product, including.
 State (solid, gas, liquid/aqueous)
 Chemical formula
 Quantity in grams, moles, or particles
 Allow you to change a reactant quantity by typing in a new value (all other quantities will update.
 All you to select unit of measure (grams, moles, or particles).
E. EXCESS REACTANT VALUES:
 Indicates the quantity of any remaining reactant
 Allows you to select unit of measure (grams, moles or particles).


The simulation calculates the theoretical yield for each reaction.
The simulation obeys standard rules of significance:
 If the last digit to be kept is followed by a digit less than 5, the number is rounded down.
 If the last digit to be kept is followed by a digit greater than 5, the number is rounded up.
 If the last digit to be kept is followed by a 5 and any additional nonzero digits, the number is rounded up.
 If the last digit to be kept is even and followed by a 5, or a 5 and additional zeros, the number is rounded
down.
 If last digit to be kept is odd and followed by a 5, or a 5 and additional zeros, the number is rounded up.
 If you enter the decimal that follows a zero, or a series of zeros, the simulation considers those zeros
significant.

The simulation uses the following values:
Avogadro’s number
6.02 x1023
Mass of hydrogen
1.01
Mass of carbon
12.01
Mass of nitrogen
14.01
Mass of oxygen
16.00
Mass of sodium
Mass of sulfur
Mass of chlorine
Mass of calcium
Mass of silver
22.99
32.07
35.45
40.08
107.87
Data and Observations:
Questions should be answered in complete sentences. Related tables, charts, and diagrams can be completed on the
Data sheet.
Part 1: Mole-Mole relationships
A. Consider the reaction between carbon dioxide and water. (Move the cursor over CO2 + H2O and click it.) The
quantity assigned to each is 1.00 mole, by default. Based on your observations, answer the following questions.
A. Write the balanced chemical equation for the reaction that occurs between carbon dioxide and water.
B. Based on the balanced equation, how many moles of product are expected if one mole of each reactant is
consumed?
C. Was there an excess, or leftover, reactant? Why or why not?
Adapted from: http://www.sascurriculumpathways.com/portal/
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B. Now change the quantity of CO2 to 3.00 moles. (Highlight the quantity displayed under the reactant CO. Type
3.00 and press Enter. Look at the results.)
D. Explain why the product yield is still 1.00 mole H2CO3.
E. When the available quantity of the first substance is not sufficient to react with the available quantity of a
second substance, the first substance is called a limiting reactant. A limiting reactant limits the amount of
product that is formed from a chemical reaction. When 3.00 moles CO2 react with 1.00 mole H2O, which
substance acts as the limiting reactant? Explain.
F. When the available quantity of the first substance is not sufficient to react with the available quantity of a
second substance, some of the second substance will remain unreacted at the end of the chemical reaction.
This substance is thus called an excess reactant. When 3.00 moles CO2 react with 1.00 mole H2O, which
substance acts as the excess reactant and what quantity remains unreacted? Explain.
C. Now change the quantity of H2O to 3.00 moles and look at the results. (Be sure to press Enter.)
G. A reaction in which the reactant coefficients are the same is described as a 1:1 reaction. What does this
description indicate about the reactant quantities needed for the reaction?
H. For a 1:1 reaction, how can you determine whether the molar quantity of one of the reactants will act to
limit the product yield?
D. Now select sodium and oxygen as the reactants. Note that 2.00 moles sodium react with 1.00 mole oxygen to
produce 1.00 mole sodium peroxide.
I. Write the complete balanced chemical equation for the reaction that occurs between sodium and oxygen.
J. The balanced chemical equation shows that the molar ratio between sodium and oxygen must be ________.
K. What would happen if 1.0 mole Na was combined with 1.00 mole O2? Use the simulation to find out.
L. Which reactant acts to limit the process? Which reactant is in excess?
M. In this example, the ratio of the reacting sodium moles to reacting oxygen moles is 1.00:0.50. Rewrite this
ratio using whole numbers.
Adapted from: http://www.sascurriculumpathways.com/portal/
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E. Now change the quantity of Na to 4.00 moles and look at the results. (Be sure to press Enter.)
N. Which reactant now acts to limit the reaction?
O. Has the ratio of reacting sodium moles to reacting oxygen moles changed?
P. For a non-1:1 reaction, such as the one that occurs between sodium and oxygen, how can you determine
whether the molar quantity of one of the reactants will act to limit the product yield?
Part 2: Mass Relationships
F. Now examine the effect of a limiting reactant upon product yield when one or more of the reactant quantities is
specified in grams.
Q. Use the simulation to collect the data needed to complete the Limiting Reactant Data Table.
 The reactants and quantities to be combined are indicated in the first two columns (Pre-reaction
Quantities).
 If the input quantity ends with a decimal (for example, 100. grams), include the decimal when you
input the number. After you click Enter, the decimal ma no longer appear in the display, but the
simulation will perform its calculations based on the significance that was represented by the
decimal.
Data Table:
 Under Post-reaction Quantities, identify the chemical formulas for each product and record the amount of each
resulting from the reaction.
 Under Remaining Reactant Quantities, record the quantity of each reactant that does not react. If no quantity
remains for a given reactant, write the number “0” in the appropriate cell.
 For some reactions, you will not need all of the columns. Simply mark any unneeded cells with an “X”.
Adapted from: http://www.sascurriculumpathways.com/portal/
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Limiting Reactant Data Table
Pre-Reaction Quantities
CH4
Cl2
1.50 mol
0.75 mol
CH4
O2
2.60 mol
6.32 mol
CaO
H2O
12.5 g
16.8 g
AgNO3
NaCl
75.3 g
68.7 g
C3H8
Cl2
88.2 g
142 g
H2SO4
NaOH
125 g
125 g
Na
H2O
45.3 g
34.1 g
Na
Cl2
100. g
100. g
C3H8
O2
175 g
182 g
Post-reaction Quantities
Remaining Reactant Quantities
CH4
g
g
g
g
g
Cl2
mol
CH4
O2
mol
mol
CaO
H2O
g
g
AgNO3
g
g
g
g
g
g
g
g
g
g
Adapted from: http://www.sascurriculumpathways.com/portal/
g
g
Cl2
g
C3H8
g
g
H2O
Na
g
g
NaOH
Na
g
g
Cl2
H2SO4
g
g
NaCl
C3H8
g
mol
g
O2
g
g
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Analysis & Conclusions:
Use the glossary in the website or the glossary in the textbook to define the following terms:
Limiting reactant/reagent –
Excess reactant/reagent -
In your own words tell me what each of the two words mean:
To determine a limiting reactant we follow the follow the same process we’ve been using in class. The only difference is
now you will need to work the calculations twice… once for each reactant. You will know which product to use because
the problem will either tell you or it won’t matter which you choose to work the problem.
1. Determine the mass, in grams, of the product when 75.0 grams Magnesium oxide reacts with 750 grams water.
A. Balance the equation.
B. Convert mass of magnesium oxide to mass of magnesium hydroxide.
_____ MgO + _____ H2O → _____ Mg(OH)2
C. Convert mass of water to mass of magnesium hydroxide.
D. _____ MgO + _____ H2O → _____ Mg(OH)2
E. Which conversion gave you the smaller amount of product? (That reactant is the limiting reactant.)
F. Which conversion gave you the larger amount of product? (That reactant is the excess reactant.)
Adapted from: http://www.sascurriculumpathways.com/portal/
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What about reactions that are not 1:1 like the previous one… the process is exactly the same.
2. What is the maximum amount of hydrogen created when 28.0 grams zinc reacts with 42.0 grams hydrochloric acid?
This kind of problem is asking more about finding the limiting reactant first. The limiting reactant determines the
maximum (most) amount of a product that can be produced.
A. Balance the equation.
B. Convert mass of zinc to mass of hydrogen.
_____ Zn + _____ HCl → _____ H2 + _____ ZnCl2
C. Convert mass of hydrochloric to mass of hydrogen.
_____ Zn + _____ HCl → _____ H2 + _____ ZnCl2
D. Which conversion gave you the smaller amount of product? (That reactant is the limiting reactant.)
E. Which conversion gave you the larger amount of product? (That reactant is the excess reactant.)
F. In this case the limiting reactant will stop the reaction so the amount of hydrogen that was created by the
limiting reactant is the maximum amount of hydrogen that can be created. What is the maximum amount of
hydrogen that can be created?
Use the glossary in the website or the glossary in the textbook to define the following terms:
1:1 reaction –
Non 1:1 reaction –
Describe in your own words what those two descriptions mean. (Use the back if necessary.)
Adapted from: http://www.sascurriculumpathways.com/portal/
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