IIT/Field Museum – High School Transformation Project
Double Replacement Reactions
Chemistry: Matter and Change (Glencoe)
Unit 3 Bonding & Reactions
Chapter 10 Chemical Reactions
Section 10.2 Classifying Chemical Reactions
Section 10.3 Reactions in Aqueous Solutions
Context of Lesson
The lesson is taught during the first semester, as students are building a repertoire of
basic chemistry skills to apply to more problems later in the year. Students have learned about
bonding and compounds and how compounds form. In this chapter, they are introduced to the
different types of reactions that occur. This lab focuses on double replacement reactions—
students will predict the outcomes of various combinations of compounds in solution, and then
investigate to determine whether their predictions are correct. This lab should be done after
students have learned to write balanced equations, ionic equations and net ionic equations in
section 10.3.
Main Goals/ Objectives:
Students will use their understanding of activity series to predict whether combinations
of six different solutions will react. Then students will receive the six solutions and test their
predictions. In doing so, students will:
 Classify reactions as double-replacement chemical reactions.
 Write balanced equations for double-replacement reactions.
 Explain that scientific knowledge should be based on empirical data.
 Explain that explanations are developed from a combination of collected data and what
is already known.
Nature of Science: Integrated Theme
 Distinguish observations from inferences, explain that inferences should be based on
observations and explain that the development of scientific knowledge involves both
observations and inferences so scientific knowledge is partially inferential.
 Explain that scientists’ background knowledge influences their doing inquiry so they may
have different observations and interpretations of the same phenomena.
 Explain that scientific knowledge should be based on empirical data.
Scientific Inquiry: Integrated Theme
 Explain that scientific investigations all begin with a question, but do not necessarily test
a hypothesis.
 Explain that there is no single scientific method and provide at least two different
methods.
 Explain that inquiry procedures are guided by the question asked.
 Explain that all scientists performing the same procedures may not get the same results.
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Explain that inquiry procedures can influence the results of an investigation.
Explain that research conclusions must be consistent with the data collected.
Explain that scientific data are not the same as scientific evidence.
Explain that explanations are developed from a combination of collected data and what
is already known.
General Alignment to Standards
State Goal 11: Understand the processes of scientific inquiry and technological design to
investigate questions, conduct experiments and solve problems.
A. Know and apply the concepts, principles and processes of scientific inquiry.
 11.A.4a Formulate hypothesis referencing prior research and knowledge
 11.A.5b Design procedures to test the selected hypotheses.
 11.A.4c Collect, organize and analyze data accurately and precisely
 11.A.4e Formulate alternative hypotheses to explain unexpected results
State Goal 12: Understand the fundamental concepts, principles and interconnections of
the life, physical and earth/space sciences.
C. Know and apply the concepts that describe properties of matter and energy and the
interactions between them.
 12.C.3b Model and describe the chemical and physical characteristics of matter.
Materials
Per student:
 Lab notebook
 Student lab sheet
 Safety Glasses
 Gloves
 Aprons
For each group of 2 students
 Micro-well plate (24 wells)
 6 dropper bottles or 6 beakers and 6 labeled pipettes (These may be shared by 2 or 3 lab
groups working at the same table)
 Approx. 2 mL of each of the following solutions
o 0.20 M aluminum sulfate (Al2(SO4)3)
o 0.20 M magnesium chloride (MgCl2)
o 0.20 M potassium hydroxide (KOH)
o 0.20 M silver nitrate (AgNO3)
o 0.20 M sodium carbonate (Na2CO3)
o 0.20 M sodium chloride (NaCl)
Supplies to be made available to all students/class
 Distilled water for rinsing well plates
 Cotton swabs for cleaning well plates
 Light and dark paper to hold beneath well plates
 Overhead transparency of solubility rules
Safety
 Remind students that lab materials are to be used ONLY as directed
 Silver Nitrate will stain EVERYTHING! Be careful using this solution. If the silver nitrate
solution gets on skin, wash immediately. Even so, there will be a brown/black stain on
the skin for several days to a week.
 The silver nitrate must be collected in a waste container. There are two safe means of
disposal.
1. Add excess salt (sodium chloride, NaCl) to the solution and mix well. This will convert
the silver nitrate into silver chloride which is insoluble in water and will constrain the
heavy metal from leaching into the landfill soil as a toxin. The mixture can be put in
the trashcan as the silver chloride form.
2. Some teachers prefer to keep the silver. Wrap a copper wire around a pencil, and
then pull the wire off to produce a tight coil of wire. Submerge the coiled wire in the
silver nitrate waste solution. The silver will precipitate onto the copper wire via a
single replacement reaction. The silver should be rinsed with water before and after
removing it from the copper coil. Put the copper coil back in the solution and repeat
until no more silver is readily obtained.
Preparation
To prepare 150 mL of each 0.20M solution, dissolve the amount of compound listed below in
enough distilled water to make 150 mL of solution.
 Al2(SO4)3…...dissolve 10.26g
 MgCl2………..dissolve 2.86g
 KOH…………..dissolve 1.68g
 AgNO3……....dissolve 5.10g
 Na2CO3……...dissolve 3.18g
 NaCl……….….dissolve 1.75g
Place the solutions in labeled dropper bottles (at least 3 bottles of each
solution, distributed around the lab) or in labeled beakers. If using beakers,
then label dropper pipettes (one pipette per solution, per lab group) by
wrapping masking tape or labeling tape around the neck of the pipette to
make a flag. Write the solution’s formula on the flag with permanent marker.
This is to prevent cross-contamination of solutions. Dropper bottles reduce
the risk of cross-contamination.
The Lesson
Bell Ringer
Before students arrive, write on the board or overhead: “You can recognize single replacement
reactions because they always involve one compound and one element on each side. What are
clues for recognizing the other four reaction types? Write your ideas.” Give students a
moment to answer, and then allow them to share their ideas with a partner.
Activity
Begin lesson by reviewing with students the fact that double replacement reactions always
occur in solution. Remind them that, just like in the single replacement lab, not every
combination of reactants will result in a reaction. Review the dissolving process for ionic
compounds and ask students: If both reactants and both replacement products are all soluble,
what happens when they are mixed? Unless a product leaves solution—generally as a
precipitate, gas, or water—no reaction occurs.
Optional – Honors Classes
Discuss with you students how reactivity and solubility will affect the outcome of a reaction.
Because the reactions depend, therefore, on whether the potential products are soluble, we
can use solubility rules to predict the outcome of combining two solutions. Demonstrate the
correct use of the solubility rules by doing a couple of examples:
 Sodium carbonate is soluble because of rule #1: salts of alkali metals are soluble.
Note that, because of the wording of rule #5, rule #1 “trumps” (overrules) it, and
sodium carbonate is soluble.
 Aluminum hydroxide is not soluble because of rule #5.
 Lead (II) chloride is not soluble because of rule #4.
Distribute the lab sheets and allow students a few moments to read them. Tell students they
must predict whether each combination of solutions will result in a reaction, then perform the
combination to see if they are correct. Their conclusions must agree with the empirical data
available—their observations in lab and their understanding of activity series.
Review for students the relevant lab safety measures—they must wear goggles, avoid getting
any solutions on their skin or clothing, clean up spills immediately, read labels carefully, follow
directions for disposal, and wash their hands after the lab. Call students’ attention to the
special treatment required for silver compounds: they should do all of their tests with the silver
nitrate solution first, then pour the contents of their well plates into the special silver collection
beaker before continuing with the tests that do not use silver. Also, remind students that bases
such as KOH are corrosive and should be rinsed off immediately if they contact the skin.
Divide students into pairs and allow them to do the lab activity. Move among students as they
work, observing their procedures, lab techniques, observations and answers. As necessary,
pose questions to make students observe more carefully or think more deeply about what they
are observing. Ask questions such as, “What’s going on in this well? Why?” Make sure to
interact with each group at least once or twice during the lab. Be alert for students who are not
following the safety guidelines and remind all students to dispose of their chemical wastes
correctly.
When most students have completed the lab and cleaned up their work areas, gather the class
back at their desks. Review students’ observations and discuss their conclusions. Discuss
possible sources of error. Ask students whether their conclusions come entirely from their
observations in lab, entirely from prior knowledge or from a combination.
Ask what
challenges students encountered as they performed the lab and allow students to comment on
one another’s conclusions and challenges.
Homework
Finish the discussion part of the lab—write equations for the reactions observed and answer
the questions.
Modifications/Accommodations
 To free up more time for the lab activity, talk briefly about solubility rules the day before
the lab and assign the predictions table for homework. Then on lab day, students may
begin testing their combinations immediately.
 To make the lab more challenging, do not provide students with pre-constructed data
tables; rather, require them to make their own data tables.
Assessment
Students’ achievement of the objectives will be assessed by observing their work in lab, their
answers to the lab questions, their answers to questions during the discussion after lab and
their work on test questions about double replacement reactions.
Double Replacement Reaction
Laboratory Investigation
When ionic compounds dissolve in water, the ions in the crystal separate and move throughout the
solution. When two such solutions are mixed, all types of positive ions in the new solution are
attracted to all types of negative ions in the solution. Sometimes a reaction takes place. This reaction
is called a double-replacement reaction. All double replacement reactions produce water, a
precipitate or a gas.
In this type of reaction, the ions of two compounds change places. Such a reaction is usually shown
as:
AB (aq) + CD (aq)
AD (aq) + CB (aq)
AB (aq)
+
CD (aq)
AD (aq)
+
CB (S)
AB (aq)
+
CD (aq)
AD (aq)
+
CB (g)
As the solutions are mixed, positive A and C ions exist in solution, as do negative B and D ions, and
these oppositely charged ions attract each other. A reaction takes place if a compound that forms
removes ions from solution.
In this lab, you will use the solubility rules to predict whether a reaction will occur when two solutions
are mixed. Then you will mix the solutions to see if your predictions are accurate.
Because you will be working with acid and other solutions (notably silver nitrate, which can cause
skin burns with a single drop), you must wear lab goggles and follow the lab safety guidelines very
carefully.
Pre-lab:
1. Read the procedure.
2. On the predictions table, fill in which ions are present in each solution. Two examples are done
for you.
3. Each box in the predictions table represents a combination of two solutions. For example, the
first blank box represents the combination of AgNO3 solution and NaCl solution. Use the charges
on the ions to predict the formulas of the possible products. One example is done for you.
Precautions:
1. Use special care when handling the AgNO3 solution. It can stain skin and clothing. If you do get
some on yourself, rinse the affected area with LOTS of water.
2. Use care also when handling the KOH solution. It is a base and can burn your skin. If you do get
some on yourself, rinse with lots of water—until the slippery feeling goes away.
Double Replacement Reaction
Laboratory Investigation Procedures
Materials:
 2 micro-well plates
 5 Dropper pipets
 5 drops of each the following solutions
o 0.20 M aluminum sulfate (Al2(SO4)3)
o 0.20 M magnesium chloride (MgCl2)
o 0.20 M potassium hydroxide (KOH)
o 0.20 M silver nitrate (AgNO3)
o 0.20 M sodium carbonate (Na2CO3)
o 0.20 M sodium chloride (NaCl)
Procedures:
 Place the two (2) micro-well plates on top of a
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NaCl Na2CO3 MgCl2 KOH Al2(SO4)3
Na2CO3
MgCl2
KOH
Al2(SO4)3
NaCl Na2CO3 MgCl2 KOH Al2(SO4)3
white piece of paper and label each row
AgNO3
and column as shown in the example
provided above.
Add five (5) drops of Al2(SO4)3, MgCl2, KOH,
Na2CO3, and NaCl to the appropriate wells
down each column. Be very careful not to
mix up the pipettes, or the solutions will
become contaminated and you will not
know what is or is not reacting!
Add five (5) drops of Al2(SO4)3, KOH,
Na2CO3, NaCl, and AgNO3 to the
appropriate wells across each row. Be very careful not to mix up the pipettes, or the solutions
will become contaminated and you will not know what is or is not reacting!
Test all combinations with silver nitrate and observe the results. Move the well plate over light
and dark surfaces to make different precipitates visible. Record your observations. Then pour
all mixtures containing silver ions into the silver waste container. Clean the well plate.
Observe and record any indication of a chemical reaction (precipitate is produced or gas is
released).
Clean up:
 Pour all of the solutions containing SILVER ions into the beaker labeled “Waste AgNO3”.
 Rinse all other combinations NOT containing silver ions down the drain with plenty of water. Any
remaining solutions may be rinsed down the drain with plenty of water.
Write up:
 For each combination that produced a precipitate or a gas, write the balanced equation. Be
sure that you have written the correct formula for each of the compounds formed in the
reactions. Then balance the equation.
Double Replacement Reaction
Laboratory Investigation Data Tables
Name: _________________________ ____________________________ Period: __________
Prediction Data Table
NaCl
Na2CO3
____ & ____ Na+ & CO32-
MgCl2
KOH
Al2(SO4)3
____ & ____ ____ & ____ ____ & ____
Na2CO3
____ & ____
MgCl2
____ & ____
KOH
____ & ____
Al2(SO4)3
____ & ____
AgNO3
Ag+ & NO3-
NaNO3
Ag2CO3
Record your observations on the table below. Write “NR” if no reaction is observed and
“PPT” if a precipitate is produced (note a brief description if you notice a reaction).
Double Replacement Data Table
NaCl
Na2CO3
MgCl2
KOH
Al2(SO4)3
AgNO3
Na2CO3
MgCl2
KOH
Al2(SO4)3
Double Replacement Reaction
Laboratory Investigation Data Tables
Prediction Data Table
NaCl
Na+ & Cl-
Na2CO3
Na+ & CO32-
MgCl2
Mg2+ & Cl-
KOH
K+ & OH-
Na2CO3
Na+ & CO32-
NR
MgCl2
Mg2+ & Cl-
MgCl2
NaCl
MgCO3
NaCl
KOH
K+ & OH-
KCl
NaOH
K2CO3
NaOH
KCl
Mg(OH)2
Al2(SO4)3
Al3+ & SO42-
AlCl3
Na2SO4
Al2(CO3)3
Na2SO4
AlCl3
MgSO4
Al(OH)3
KSO4
AgNO3
Ag+ & NO3-
AgCl
NaNO3
AgCO3
NaNO3
AgCl
Mg(NO3)2
AgOH
KNO3
Al2(SO4)3
Al3+ & SO42-
Ag2SO4
Al(NO3)
Record your observations on the table below. Write “NR” if no reaction is observed and
“PPT” if a precipitate is produced (note a brief description if you notice a reaction).
Double Replacement Data Table
NaCl
Na2CO3
MgCl2
KOH
Na2CO3
NR
MgCl2
NR
PPT
KOH
NR
NR
PPT
Al2(SO4)3
NR
PPT
NR
PPT
AgNO3
PPT
PPT
PPT
PPT
Al2(SO4)3
PPT
Discussion:
1. Write the balanced equation for the reactions that produced a precipitate (label the precipitate
with (s)). Be sure to verify that you have the correct formula for each compound before you
balance the equation!
2. Choose two of the equations from Question 1 and rewrite them as ionic and net ionic equations.
3. Identify any cases where your data was different from your predictions. Offer explanations of
possible sources of error.
4. Using your understanding of activity series, write down the equation for two reactions that took
place but did not produce an observable reaction.
Discussion:
1. Write the balanced equation for each of the expected reactions. Label the expected precipitate
with (s). (Be sure to verify that you have the correct formula for each compound before you
balance the equation!)
NaCl (aq) + AgNO3 (aq)  NaNO3 (aq) + AgCl (s)
Na2CO3 (aq) + 2 AgNO3 (aq)  2 NaNO3 (aq) + Ag2CO3 (s)
MgCl2 (aq) + 2 AgNO3 (aq)  Mg(NO3)2 (aq) + 2 AgCl (s)
KOH (aq) + AgNO3 (aq)  KNO3 (aq) + AgOH (s)
Al2(SO4)3 (aq) + 6 AgNO3 (aq)  2 Al(NO3)3 (aq) + 3 Ag2SO4 (s)
Al2(SO4)3 (aq) + 3 Na2CO3 (aq)  Al2(CO3)3 (s) + 3 Na2SO4 (aq)
Al2(SO4)3 (aq) + 6 KOH (aq)  2 Al(OH)3 (s) +3 K2SO4 (aq)
MgCl2 (aq) + 2 KOH (aq)  2 KCl (aq) + Mg(OH)2 (s)
Na2CO3 (aq) + MgCl2 (aq)  2 NaCl (aq) + MgCO3 (s)
2. Choose two of the equations from number 3 and rewrite them as ionic and net ionic equations.
Answers will vary. An example:
Ionic: Na+ (aq) + Cl- (aq) + Ag+ (aq) + NO3- (aq)  Na+ (aq) + NO3- (aq) + AgCl (s)
Net ionic: Ag+ (aq) + Cl- (aq)  AgCl (s)
3. Identify any cases where your data was different from your predictions. Offer explanations of
possible sources of error.
Possible sources of error will vary but may include contamination of droppers or wells, using the
wrong solution or not enough of it, and not waiting long enough to see a reaction.
4. Using your understanding of activity series, write down the equation for two reactions that took
place but did not produce an observable reaction.
Answers will vary. An example:
NaCl (aq) + KOH (aq)  NaOH (aq) + KCl (aq)
Since sodium (Na) and potassium (K) are both alkali and alkali salts are soluble, they will not form
a precipitate. A double replacement reaction takes place since the more reactive potassium (K)
replaces the sodium (Na) to form potassium chloride (KCl) and the sodium bonds to the hydroxide
to form sodium hydroxide (NaOH).
Solubility Rules
1. Salts of alkali metals (group I) and ammonium are soluble, EXCEPT a few lithium
compounds.
2. Nitrate and chlorate salts are soluble.
3. Sulfate salts are soluble. EXCEPT lead (Pb), silver (Ag), mercury (Hg), barium (Ba), strontium
(Sr), and calcium (Ca).
4. Chloride salts are soluble. EXCEPT lead (Pb), silver (Ag), and mercury (Hg).
5. Carbonates, phosphates, chromates, sulfides, and hydroxides are insoluble unless they are
listed as soluble above.