Experiment
5.2
Calculations with a Chemical Reaction (4)
Lab = 126
(5) Introduction:
Every balanced chemical equation tells you the
relative number of moles of the substances
involved in the reaction. The familiar equation
2H2 + O2  2H2O
tells you that when 2 moles of hydrogen
molecules react with 1 mole of oxygen
molecules, 2 moles of water molecules are
produced. Equations deal with moles, but tools
used in the laboratory - balances, graduated
cylinders, or pipets - do not measure moles
directly. It is necessary to convert mass to moles
by using the molar mass of a substance or to
convert volume to moles by using the molarity of
a solution. In this experiment, the reactants are
dissolved in water, and the concentrations of the
solutions are expressed in molarity - moles per
liter of solution (M).
The reaction takes place between solutions of
calcium chloride and sodium carbonate. The
products are calcium carbonate and sodium
chloride. Because sodium chloride is soluble, it
will remain in solution. However, calcium
carbonate is insoluble in water. It will form a
precipitate. You will collect the calcium
carbonate by filtration, dry it, and determine the
mass of this product of the reaction.
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(2) Objectives:
1. Observe the reaction between solutions of
calcium chloride and sodium carbonate.
2. Calculate the number of moles of each
reactant and determine the reactant that is
in excess.
3. Determine the theoretical yield of calcium
carbonate and compare it to the actual
amount produced.
4. Calculate the percent yield.
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(5) Materials:
analytical balance
burets
filter paper
18 X 150 test tube
test tube rack
50 mL beakers
safety goggles
laboratory apron
Reagents:
0.60 M sodium carbonate solution, Na2CO3
0.40 M calcium chloride solution, CaCl2
deionized water
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Procedure:
Day 1
1. Adorn your laboratory apron and safety
glasses.
2. Locate the buret labeled 0.40 M CaCl2. If it is
not at least half full, use a clean, small,
labeled, beaker to add 0.40 M CaCl2 to
between the 0 and 5 mL marks on the buret.
3. Read the buret to the nearest 0.01 mL. Have
each partner verify the reading, and record
this initial reading in your data table. Have
the teacher verify the reading and give the
STAMP of approval.
4. Add approximately 30 mL of the 0.40 M CaCl2
from the buret into your clean 100 mL
beaker. (Think about where the meniscus
Experiment 5-2
needs to stop at…sorry you’re going to have
to think.)
5. Read the buret to the nearest 0.01 mL. Have
each partner verify the reading, and record
this final reading in your data table.
6. Locate the buret labeled 0.60 M Na2CO3. If it
is not at least half full, use a clean, small,
labeled, beaker to add 0.60 M Na2CO3 to
between the 0 and 5 mL marks on the buret.
7. Read the buret to the nearest 0.01 mL. Have
each partner verify the reading, and record
this initial reading in your data table.
8. Add approximately 15 mL of the 0.60 M
Na2CO3 from the buret into the 100 mL
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rinse the beaker 3 times with ≈5 mL of
deionized water, and pour the rinse water
into the filter paper.
beaker containing your 0.40 M CaCl2
solution. (Again…think)
9. Read the buret to the nearest 0.01 mL. Have
each partner verify the reading, and record
this final reading in your data table.
10. Stir the reaction mixture for 15 seconds and
then allow the solid to settle for at least three
minutes.
11. Obtain a clean, dry piece of filter paper and
a clean, dry 100 mL beaker and record its
masses together on analytical balance.
Record the ID of your beaker.
12. Make cold DI water by putting DI ice cubes
in your water bottle. Use vacuum filtration to
filter your precipitate. There are four filter
stations, so be patient and work efficiently.
13. Slowly pour the mixture from the beaker into
the filter paper, using your stir rod as your
guide. Use your wash bottle to rinse all solid
from the beaker into the filter paper. Then
14. Allow the filter paper to drain. Rinse the filter
paper with deionized water. That's once.
Allow the filter paper to drain. Rinse the filter
paper with deionized water. That's twice.
Allow the filter paper to drain. Rinse the filter
paper with deionized water. That's thrice.
Allow the filter paper to drain. Discard filtrate
down the drain.
15. Fold the filter paper in fourths and place the
filter paper into your clean, dry beaker. You
may have to press down at the center to get
the filter paper into the beaker.
16. Place the filter paper and the beaker into a
drying oven at 90-100°C overnight.
17. Clean and return all materials to their proper
places. Sponge your counter top. Wash your
hands
Day 2
19. Retrieve your beaker from the drying oven.
Allow it to cool, and determine the mass of
the filter paper with precipitate. Obtain the
STAMP of Approval.
20. Discard filter paper and precipitate in waste
can.
21. Be sure all equipment in your drawer and
cabinet is clean and neat before leaving lab.
.
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Experiment 5-2
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Data and Observations:
(48) Data Table 1: Primary Data
(4) CaCl2, final reading
(4)
CaCl2, initial reading
(4) CaCl2, volume delivered
(4) Na2CO3, final reading
(4) Na2CO3, initial reading
(4) Na2CO3, volume delivered
(4) mass of dry ppt and filter paper/beaker
(4) mass of filter paper and beaker
(4) mass of precipitate
(2) beaker ID number
Observations (10):
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Experiment 5-2
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(14) Data Table 2: Secondary Data (2 pts each)
Moles of sodium carbonate used
Moles of calcium chloride used
Moles of calcium carbonate produced
Write a balanced equation for the
reaction you observed in this
experiment.
Which of the reactants was in
excess? Why?
Mass of calcium carbonate that
should, theoretically, form from the
amount limiting reactant.
Percent Yield of your reaction
(14) Calculations:
For each of the calculations show your derivation
including dimensional analysis.
(2) 5. Write a balanced equation for the reaction you
observed in this experiment.
1. Complete secondary data in the data table.
(2) 6. Show which of the reactants was in excess in
this reaction. Justify your answer.
(2) 2. Determine the moles of sodium carbonate used.
(2) 3. Determine the moles of calcium chloride used.
(2) 4. Determine the moles of calcium carbonate
produced.
(2) 7. Calculate the mass of calcium carbonate that
should, theoretically, form from the amount of
limiting reactant.
(2) 8. Calculate the percent yield of your reaction.
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(18) Analysis:
(6) 1. List three specific sources of error in this
experiment.
2. Predict if percent yield would be higher, lower,
or the same as it should be if the following
occurred: (explain your reasoning)
(4) b. Some precipitate remained in the reaction
beaker.
(4) c. The solution passing through the filter was
not clear.
(4) a. The solid was not completely dry.
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Experiment 6-1
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(16) Synthesis:
(4) 1. What volume of 0.60 M sodium carbonate
would be just enough to completely react with
the amount of 0.40 M calcium chloride used
in this experiment?
(4) 2. Using the moles of CaCl2 from experiment,
what mass of calcium carbonate would be
produced, assuming 100% yield?
Experiment 6-1
(4) 3. Using the moles of CaCl2 from experiment,
what mass of sodium chloride would be
produced, assuming 100% yield?
(4) 4. How could you recover the sodium chloride
produced in this experiment from the filtrate?
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