VLab: Limiting Reactants: Data & Observations
All questions are to be answered on your own paper. Related tables, charts, and diagrams can be
completed on the Data Sheet (PDF) provided by your teacher.
Part 1: Mole-Mole Relationships
A. Consider the reaction between carbon dioxide and water. (Move the cursor over CO2 +
H2Oand click it.) The quantity assigned to each is 1.00 mole, by default. Based on your
observations, answer the following questions.
1. Write the balanced chemical equation for the reaction that occurs between carbon
dioxide and water.
2. Based on the balanced equation, how many moles of product are expected if one
mole of each reactant is consumed?
3. Was there an excess, or leftover, reactant? Why or why not?
B. Now change the quantity of CO2 to 3.00 moles. (Highlight the quantity displayed under
the reactant CO2. Type 3.00 and press Enter. Look at the results.)
4. Explain why the product yield is still 1.00 mole H2CO3.
5. 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.
6. 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 moleH2O, 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.)
7. A reaction in which the reactant coefficients are the same is described as
a 1:1reaction. What does this description indicate about the reactant quantities
needed for the reaction?
8. 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
with1.00 mole oxygen to produce 1.00 mole sodium peroxide.
9. Write the complete balanced chemical equation for the reaction that occurs
between sodium and oxygen.
10. The balanced chemical equation shows that the molar ratio between sodium and
oxygen must be ___________________.
11. What would happen if 1.00 mole Na was combined with 1.00 mole O2? Use the
simulation to find out.
12. Which reactant acts to limit the process? Which reactant is in excess?
13. In this example, the ratio of reacting sodium moles to reacting oxygen moles
is1.00:0.50. Rewrite this ratio using whole numbers.
E. Now change the quantity of Na to 4.00 moles and look at the results. (Be sure to press
Enter.)
14. Which reactant now acts to limit the reaction?
15. Has the ratio of reacting sodium moles to reacting oxygen moles changed?
16. 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.
17. 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 may
no longer appear in the display, but the simulation will perform its calculations
based on the significance that was represented by the decimal.
VLab: Limiting Reactants: Analysis & Conclusions
Solving Problems: 1:1 Reactions
The process for solving a 1:1 limiting reactant problem is outlined below. The process is applied to the
following problem:
Determine the mass, in grams, of each product that results from the reaction of 75.0 grams magnesium
oxide with 75.0 grams water.
A. Write the complete balanced equation for the chemical reaction.
MgO + H2O Mg(OH)2
B. Convert reactant quantities to moles, if not given as such, using dimensional analysis.
C. Identify the limiting reactant. For 1:1 reactions, the limiting reactant is the reactant
with the smaller molar quantity available.
Magnesium oxide limits the reaction; only 1.86 moles MgO are available to react.
D. Determine the difference between the molar reactant quantities; this difference
represents the moles of excess reactant.
1.86 moles MgO will react with an equivalent molar quantity of H2O. 1.86
moles H2O react, leaving 2.31 moles (4.17 moles - 1.86 moles) of
excess H2O unreacted.
E. Convert the moles of excess reactant to grams, using dimensional analysis.
F. Use the moles of limiting reactant to determine the quantities of each product that
forms. Separate dimensional analysis set-ups are required to calculate each product
quantity, which can be specified in either moles or grams.
The moles of the limiting reactant are multiplied by the molar ratio between the product
and the limiting reactant, as specified by the coefficients from the balanced equation.
The moles of the product, Mg(OH)2, are then converted to grams, using the masses
provided by the periodic table.
When 75.0 grams magnesium oxide react with 75.0 grams water, 108
grams Mg(OH)2 are produced.
Look at the results for the fourth reaction in the Limiting Reactant Data Table. Use the steps outlined
below to analyze the reaction between 75.3 grams silver nitrate and 68.7 grams sodium chloride. Work
out each step on your own so that you will understand the process fully.
1. Write the complete balanced equation for the chemical reaction.
2. Convert reactant quantities to moles, using dimensional analysis.
3. Identify the limiting reactant.
4. Calculate the moles of excess reactant.
5. Convert the moles of excess reactant to grams, using dimensional analysis.
6. Use the moles of limiting reactant to determine the quantities (in grams) of each
product that forms.
Now that you've been stepped through the process for completing 1:1 limiting reactant problems, you can
analyze some of the data from the Limiting Reactant Data Table.
7. In the reaction between sodium and water, why does water act as the limiting reactant?
8. In the reaction between propane (C3H8) and chlorine, why was there no excess
reactant?
9. Explain how the reaction between silver nitrate and sodium chloride obeys the law of
conservation of mass.
Use the problem-solving technique you've learned to work out the following 1:1 limiting reactant problems.
10. If 65 grams silver nitrate react with 45 grams sodium bromide, how many grams of
sodium nitrate will be formed?
11. If 115 grams magnesium oxide react with 82.5 grams water, how many grams of
excess reactant remain?
Solving Problems: Non-1:1 Reactions
The process for solving a non-1:1 limiting reactant problem is outlined below. The process is applied to
the following problem:
Determine the mass, in grams, of each product that results from the reaction of 28.0 grams zinc with 42.0
gramshydrochloric acid.
A. Write the complete balanced equation for the chemical reaction.
Zn + 2 HCl H2 + ZnCl2; This is a non-1:1 reaction, since the coefficients for the two
reactants differ.
B. Convert reactant quantities to moles, if not given as such, using dimensional analysis.
These quantities represent the available moles for each reactant.
C. (A) Determine the molar quantity of the second reactant that would be required for the
available moles of the first reactant to react completely.
(B) Likewise, determine the molar quantity of the first reactant that would be required
for the available moles of the second reactant to react completely.
Calculate these quantities using dimensional analysis. The result indicates how many
moles of each reactant are needed.
(A)
0.856 mole HCl is required to react with all of the available zinc.
(B)
0.575 mole Zn is required to react with the available moles of hydrochloric acid.
D. Compare the available quantities to the needed quantities. The substance for which the
available quantity is less than the needed quantity is the limiting reactant.
Comparing the available and needed molar quantities for the reactants reveals that
there is insufficient zinc to react with the available hydrochloric acid; 1.15 moles HCl
will react with0.575 mole Zn, yet only 0.428 mole Zn is available. Therefore, zinc limits
the reaction yield and acts as the limiting reactant for this process.
E. Calculate the moles of excess reactant by subtracting the amount needed to react with
the limiting reactant from the amount available.
mole(s) excess reactant = moles available - moles needed
mole(s) excess HCl = (1.15 - 0.856) moles HCl
mole(s) excess HCl = 0.294 mol HCl (0.29 if rounded for significance)
F. Convert the moles of excess reactant to grams, using dimensional analysis.
When 28.0 grams zinc are added to 42.0 grams HCl, 10.6 grams HCl remain unreacted
after all of the zinc is consumed.
G. Use the moles of limiting reactant to determine the quantities of each product that
forms. Separate dimensional analysis setups are required to calculate each product
quantity, which can be specified in either moles or grams.
The moles of the limiting reactant are multiplied by the molar ratio between the product
and the limiting reactant, as specified by the coefficients from the balanced equation.
The moles of the product are then converted to grams, using the masses provided by
the periodic table.
58.2 grams ZnCl2 and 0.865 gram H2 are produced when 28.0 grams zinc react
with42.0 grams hydrochloric acid.
12. Compare the solution processes for 1:1 and non-1:1 reactions. Explain how the limiting
reactant is identified in each case.
Now analyze the data for non-1:1 reactions from the Limiting Reactant Data Table, using the problemsolving technique outlined above.
13. In the reaction between sulfuric acid and sodium hydroxide, why did 23 grams sodium
hydroxide remain unreacted?
14. In the reaction between propane (C3H8) and oxygen, why were only 150. grams carbon
dioxide produced?
Use the problem-solving technique you've learned to work out the following non-1:1 limiting reactant
problem.
15. If a mixture of 100. grams iron (III) nitrate and 100. grams zinc are allowed to react,
how many grams of the resulting compound are formed?
The simulation calculates the theoretical yield for a chemical reaction. From your earlier studies of
stoichiometry, recall that percent yield is calculated as follows:
16. Use your knowledge of percent yield and limiting reactant calculations to solve the
following problem. Calculate the percent yield of the reaction of 205 grams aluminum
hydroxide with751 grams hydrogen sulfate (sulfuric acid), given that 252
grams aluminum sulfate are produced.