Course: Chemistry
Grade Level: 10-12
Type: Informational/Explanatory
Structure: Synthesis
Teaching Task 18: After researching informational texts, writing a background/information
section and developing a hypothesis, conduct an experiment on the selected topic. Upon
completion of the experiment, write a formal lab report that explains the results and confirms or
rejects the hypothesis. What conclusion or implications can you draw? Cite at least 2 sources,
pointing out key elements from each source. A bibliography in APA format is required.
Performance Level: Advanced
Purpose:
The purpose of this experiment is to observe reactions between ionic solutions, use the solubility
chart to predict products that will form a precipitate, and to correctly write the double replacement
reactions which occur.
Background Information:
A chemical reaction is defined as a change in which one or more reactants change into one or
more products. It is characterized by the breaking of bonds in reactants and the formation of
bonds in products (Gelder). When a chemical reaction occurs, a chemical equation is formed.
A chemical equation is an expression representing a chemical reaction. The formulas of the
reactants, on the left, are connected by an arrow to the formulas for the products, on the right
(Gelder). The law of conservation of mass which influences chemical reactions, states that in
any physical or chemical reaction, mass is conserved. Mass can neither be created nor destroyed
(Gelder). There are many types of reactions, one of these being the double replacement reaction.
A double replacement is a chemical change that involves an exchange of positive ions between
two compounds (Gelder). Precipitates are formed as results of double replacement reactions.
A precipitate is a solid that forms and settles out of a liquid mixture (Gelder). Solubility charts
are used to show which ion forms a precipitate. It summarizes the solubility behavior for a large
group of ionic compounds. It can also be used to determine whether an ionic compound is an
aqueous solution, meaning soluble, or as a solid, insoluble (Wilbraham).
Hypothesis:
1. If silver nitrate is reacted with barium chloride, than silver chloride will form a
precipitate and aqueous barium nitrate will be produced because it is a double
replacement reaction and the silver and barium ions trade places. (RXN #2)
2. If silver nitrate is reacted with calcium nitrate, then no reaction will occur because neither
of them formed an insoluble precipitate. (RXN #4)
3. If silver nitrate is reacted with potassium phosphate, then silver phosphate will form
a precipitate and aqueous potassium nitrate will be produced because it is a double
replacement reaction and the silver and potassium ions trade places. (RXN #5)
4. If sodium carbonate is reacted with calcium nitrate, then calcium carbonate will form
a precipitate and aqueous sodium nitrate will be produced because it is a double
replacement reaction and the sodium and calcium ions trade places. (RXN #8)
5. If barium chloride is reacted with ammonium sulfate, then barium sulfate will form a
precipitate and aqueous ammonium chloride will be produced because it is a double
replacement reaction and the barium and ammonium ions trade places. (RXN #10)
6. If barium chloride is reacted with potassium phosphate, then barium phosphate will form
a precipitate and aqueous potassium chloride will be produced because it is a double
replacement reaction and the barium and potassium ions trade places. (RXN #12)
Materials:
1. silver nitrate
2. sodium carbonate
3. barium chloride
4. ammonium sulfate
5. calcium nitrate
6. potassium phosphate
7. test plate
Procedures:
1. Combined 5 drops of each solution in a test plate well. If a solid formed at the bottom
or the solution turned cloudy, recorded that a precipitate formed on the data table.
Continued until all combinations were completed.
2. When finished, thoroughly cleaned the test plates, and returned them and the dropper
bottles to the proper place.
Results:
Data Table #1 - Reactants and Predicted Products
RXN #
Reactants
Predicted Products
Precipitate?
2
AgNO3
BaCl2
Ba(NO3)2
AgCl
Yes, AgCl
4
AgNO3
Ca(NO3)2
Ca(NO3)2
AgNO3
No, NR
5
AgNO3
K3PO4
KNO3
Ag3PO4
Yes, Ag3PO4
8
Na2CO3
Ca(NO3)2
CaCO3
NaNO3
Yes, CaCO3
10
BaCl2
(NH4)2SO4
NH4Cl
BaSO4
Yes, BaSO4
12
BaCl2
K3PO4
KCl
Ba3(PO4)2
Yes, Ba3(PO4)2
Data Table #2 - Observations
Reaction #
Name of Reactant Solutions
Precipitate Description
2
silver nitrate
barium chloride
very white and cloudy
precipitate
4
silver nitrate
NR
calcium nitrate
5
silver nitrate
potassium phosphate
yellow and cloudy precipitate
8
sodium carbonate
calcium nitrate
white and slightly cloudy
precipitate
10
barium chloride
ammonium sulfate
white and cloudy precipitate
12
barium chloride
potassium phosphate
white and slightly cloudy
precipitate
Balanced Equations:
1.)
2AgNO3 + BaCl2 ----> Ba(NO3)2 + 2AgCl↓
2.)
AgNO3 + Ca(NO3)2 ----> NR
3.)
3AgNO3 + K3PO4 ----> 3KNO3 + Ag3PO4↓
4.)
Na2CO3 + Ca(NO3)2 ----> CaCO3↓ + 2NaNO3
5.)
BaCl2 + (NH4)2SO4 ----> 2NH4Cl + BaSO4↓
6.)
3BaCl2 + 2K3PO4 ----> 6KCl + Ba3(PO4)2↓
(RXN #2)
(RXN #4)
(RXN #5)
(RXN #8)
(RXN #10)
(RXN #12)
Discussion and Conclusion:
The purpose of this experiment is to observe reactions between ionic solutions, use the
solubility chart to predict products that will form a precipitate, and to correctly write the double
replacement reactions which occur. Because of the data and correct hypothesis, the purpose of
this experiment was achieved.
Results Recap
Reaction #2: When aqueous silver nitrate reacted with aqueous barium chloride an AgCl
precipitate formed and aqueous Ba(NO3)2 was produced. This indicates that a reaction occurred
between silver nitrate and barium chloride. 2AgNO3 + BaCl2 ----> Ba(NO3)2 + 2AgCl↓ is the
chemical equation for the reaction.
Reaction #4: When silver nitrate and calcium nitrate were combined no reaction was observed.
AgNO3 + Ca(NO3)2 ----> NR is the chemical equation that shows no reaction occurred.
Reaction #5: When aqueous silver nitrate reacted with aqueous potassium phosphate an Ag3PO4
precipitate formed and aqueous KNO3 was produced. This indicates that a reaction occurred
between silver nitrate and potassium phosphate. 3AgNO3 + K3PO4 ----> 3KNO3 + Ag3PO4↓ is
the chemical equation for the reaction.
Reaction #8: When aqueous sodium carbonate reacted with aqueous calcium nitrate a CaCO3
precipitate formed and aqueous NaNO3 was produced. This indicates that a reaction occurred
between sodium carbonate and calcium nitrate. Na2CO3 + Ca(NO3)2 ----> CaCO3↓ + 2NaNO3 is
the chemical equation for the reaction.
Reaction #10: When aqueous barium chloride reacted with aqueous ammonium sulfate a BaSO4
precipitate formed and aqueous NH4Cl was produced. This indicates that a reaction occurred
between barium chloride and ammonium sulfate. BaCl2 + (NH4)2SO4 ----> 2NH4Cl + BaSO4↓ is
the chemical equation for the reaction.
Reaction #12: When aqueous barium chloride reacted with aqueous potassium phosphate a
Ba3(P04)2 precipitate formed and aqueous KCl was produced. This indicates that a reaction
occurred between barium chloride and potassium phosphate. 3BaCl2 + 2K3PO4 ----> 6KCl +
Ba3(PO4)2↓ is the chemical equation for the reaction.
Hypothesis Acceptance or Rejection
Reaction #2: The hypothesis that silver nitrate when reacted with barium chloride will produce
a silver chloride precipitate and aqueous barium nitrate is accepted because a very white and
cloudy precipitate was formed as predicted by the solubility chart.
Reaction #4: The hypothesis that silver nitrate when reacted with calcium nitrate will result in no
precipitate is accepted because no reaction occurred.
Reaction #5: The hypothesis that silver nitrate when reacted with potassium phosphate will
produce a silver phosphate precipitate and aqueous potassium nitrate is accepted because a
yellow and cloudy precipitate was formed as predicted by the solubility chart.
Reaction #8: The hypothesis that sodium carbonate when reacted with calcium nitrate will
produce a calcium carbonate precipitate and aqueous sodium nitrate is accepted because a white
and slightly cloudy precipitate was formed as predicted by the solubility chart.
Reaction #10: The hypothesis that barium chloride when reacted with ammonium sulfate will
produce a barium sulfate precipitate and aqueous ammonium chloride is accepted because a
white and cloudy precipitate was formed as predicted by the solubility chart.
Reaction #12: The hypothesis that barium chloride when reacted with potassium phosphate will
produce a barium phosphate precipitate and aqueous potassium chloride is accepted because a
white and slightly cloudy precipitate was formed as predicted by the solubility chart.
Sources of Error
When constructing an experiment it is possible that the results will not be 100% accurate. In this
experiment there are a few things that could lead to inaccurate results. When the drops of each
chemical were dropped into the test plate wells, it is possible that the incorrect number of drops
could have been added. Furthermore, what was thought to be in a certain test plate well could
have been in another. It would not be hard to mix them up because they all look fairly similar.
Lastly, the test plates may not have been completely cleaned out before the experiment. The
residue from past experiments could have affected the results of this experiment. In conclusion,
any of these things could have contributed to inaccurate results for this experiment.
Works Cited:
Gelder, Dr. John I. "Chapter 7." OSU Chemistry Courses. N.p., n.d. Web. 30 Apr.
2012. <http://intro.chem.okstate.edu/1215/lecture/chapter7/
lecture92898.html>.
Wilbraham, Antony C., et al. Chemistry. Boston: Pearson Prentice Hall, 2008.
Print.
Annotation
Focus
4 Reading/Research 4 Controlling Idea
4 Development
4
Organization
4
Conventions
4
Content
Understanding
4
This focused lab report addresses all aspects of the prompt by
clearly developing the hypotheses, predicting the products and
forming a strongly developed discussion and conclusion. The writer presents relevant background research and information
pertaining to all parts of the prompt.
The writer includes thorough explanations throughout the
laboratory report that distinctly connect back to the purpose:
The purpose of this experiment is to observe reactions between
ionic solutions, use the solubility chart to predict products that will
form a precipitate, and to correctly write the double replacement
reactions which occur.
The writer accurately predicts products for double replacement
reactions: If silver nitrate is reacted with potassium phosphate, then
silver phosphate will form a precipitate and aqueous potassium
nitrate will be produced because it is a double replacement
reaction and the silver and potassium ions trade places. The writer
provides complete and balanced chemical equations: 3AgNO3 +
K3PO4 à 3KNO3 + Ag3PO4 ↓ . A thorough statement about the
chemical reactions that accepts or rejects the writer’s hypotheses
supports the purpose: The hypothesis that silver nitrate when
reacted with potassium phosphate will produce a silver phosphate
precipitate and aqueous potassium nitrate is accepted because a
yellow and cloudy precipitate was formed as predicted by the
solubility chart.
The writer includes clear, descriptive headings and sub-headings in
a logical sequence throughout the entire laboratory report. The
organization enhances the overall quality of the laboratory report.
For example, the writer includes clear, well-developed data tables
with descriptive headings.
The writer demonstrates a strong command of the English language
and scientific vocabulary with very few errors that do not affect the
readability of the laboratory report.
The writer demonstrates an in-depth understanding of the chemistry
concepts and structure of a formal laboratory report. The writer
• Includes the precipitate arrow (↓) in the chemical equation
as shown.
• Includes sub-headings, such as “Results Recap,”
“Hypothesis Acceptance or Rejection,” and “Sources of
Error” in the conclusion section of the report.
This student would benefit from feedback, discussion, and/or instruction in the following
areas:
•
•
Standard APA formatting of the parenthetical citation
Opportunities to share the laboratory report with an audience
o This laboratory report with its exemplary attention to detail, thoroughness and
structure could serve as a model laboratory report