Experiment
3.2
Types of Chemical Reactions (4)
T=106
(5) Introduction
In this laboratory exercise, you will differentiate
among five general types of chemical reactions.
You will carry out certain representative reactions
yourself, while your teacher will demonstrate
others. From your observations you will attempt to
identify the products of each reaction and to
determine the type of reaction that has taken
place. The types of reaction you will consider are:
synthesis (combination) reactions, decomposition
reactions,
single
displacement
(single
replacement) reactions, double displacement
(double replacement) reactions, and combustion
reactions. The majority of common chemical
reactions can be classified as belonging to one of
these categories.
Synthesis reactions, also called combination
reactions, are reactions in which two or more
substances combine to form a single product. The
reactants may be elements or compounds, but the
product is always a single compound. An example
of a combination reaction is the reaction between
sulfur trioxide and water to form sulfuric acid.
SO3(g) + H2O(l) -----> H2SO4(aq)
Decomposition reactions are reactions in which
a single substance breaks down into two or more
simpler substances. There is always just a single
reactant in a decomposition reaction. An example
of a decomposition reaction is the breakdown of
calcium carbonate upon heating.
CaCO3(s) + heat -----> CaO(s) + CO2(g)
Single replacement reactions, also known as
single displacement reactions, are reactions in
which an element within a compound is displaced
by a separate element. This type of reaction
always has two reactants, one of which is always
an element. An example of a single replacement
reaction is the reaction of zinc metal with
hydrochloric acid.
Zn(s) + 2HCl(aq) --> ZnCl2(aq) + H2(g)
Double replacement reactions, also known as
double displacement reactions, are reactions in
which a positive ion from one ionic compound
exchanges with the positive ion of another ionic
compound. These reactions typically occur in
aqueous solution and result in either the formation
of a precipitate, the formation of a gas, or the
formation of a molecular compound such as
water. An example of a double replacement
reaction is the reaction that occurs between
aqueous silver nitrate and aqueous sodium
chloride. A precipitate of solid silver chloride is
formed in this reaction.
AgNO3(aq) + NaCl(aq) --> AgCl(aq) + NaNO3(aq)
Combustion reactions are reactions in which an
element or a compound reacts rapidly with
oxygen gas to liberate heat and light energy.
Commonly, the compounds combining with
oxygen in these reactions are hydrocarbons,
compounds consisting wholly of hydrogen and
carbon. The burning of ethane is an example of a
combustion reaction.
C2H4(g) + O2(g) -----> CO2(g) + H2O(g)
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(2) Objectives
1. To observe chemical reactions in order to
determine the reaction type.
2. To write balanced chemical equations for each
reaction.
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Equipment
Student Experiment
1 safety goggles & apron
4 13x100 test tubes
2 18x150 test tubes
1 gas burner
striker
1 test tube clamp
test tube rack
steel wool
plastic wrap
50 mL Erlenmeyer Flask
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Experiment 3.2
Page 1
(5) Materials
Student Experiment
iron nail, Fe
copper (II) sulfate pentahydrate, CuSO4·5H2O
magnesium, turnings, Mg
magnesium, ribbon, Mg
0.1M copper(II) sulfate, CuSO4
0.1M lead(II) nitrate, Pb(NO3)2
0.1M potassium iodide, KI
3% hydrogen peroxide, H2O2
6M hydrochloric acid, HCl
wood splints
manganese(IV) oxide
sodium bicarbonate, NaHCO3
limewater, saturated solution of calcium oxide,
CaO
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Safety
1. Wear safety goggles.
2. Hydrochloric acid is corrosive and can cause
severe injury. If you spill acid on yourself,
immediately flush the affected area with water
for 2-3 minutes and notify the teacher. If acid
should get into your eyes, begin flushing your
eyes in the eyewash with water immediately
and continue to do so for at least 15 minutes.
3. If acid is spilled on the laboratory bench or
floor, neutralize the spill with solid sodium
bicarbonate (baking soda), before wiping it up
with sponges or paper towels. Always
neutralize acids before pouring down the
drain. There is a neutralization beaker in the
sink. Pour any liquid from the beaker, then
add your acid. If it does not effervesce, add
baking soda.
4. Copper(II) sulfate is an irritant. Avoid skin
contact with this chemical. Wash your hands
thoroughly after use.
5. Lead and copper compounds are poisonous,
bioaccumulative, and are water pollution
hazards. Use as little of these compounds as
possible. Place their waste in proper waste
bottles. Wash your hands thoroughly after
use.
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Procedure
1. Iron metal and copper(II) sulfate solution.
Fill a 13x100 test tube halfway with 0.1 M
copper(II) sulfate solution. Add a clean shiny
iron nail. Observe the reaction after 10
minutes. Record your observations in the
data table. Discard the solid contents of the
test tube into the waste can. The liquid
portion can be poured into the sink.
2.
Lead(II) nitrate and potassium iodide
solutions. Put ≈2 mL of 0.1 M lead(II) nitrate
solution in a 13x100 test tube. Add 5 to 10
drops of 0.1 M potassium iodide solution.
Record your observations.
Discard the
contents of the test tube into the “Heavy
Metal” container and rinse the tube with
water.
3. Action of heat on copper(II) sulfate crystals.
Put a microspoonful of copper(II) sulfate
pentahydrate into a 18 mm X 150 mm, dry
test tube. Fasten a utility clamp to the upper
end of the test tube. Hold the tube by the
clamp so that it is almost parallel to the
surface of the lab bench. CAUTION: Do not
point the open mouth of the tube at yourself or
anyone else. Make observations as you
gently heat the crystals in a burner flame for
approximately 30 seconds. Heat only the
Experiment 3.2
bottom of the tube, where the crystals are
located. When the test tube has cooled,
discard its contents into the “Heavy Metal
Waste” container provided.
4.
Magnesium metal and hydrochloric acid.
Fill one medium-size (13 X 100 mm) test tube
one-fourth full with 6 M hydrochloric
acid..CAUTION :
Hydrochloric acid is
corrosive. Place the test tube in a test tube
rack. Put three or four magnesium turnings
into the acid solution. If you observe a gas
forming, test for its identity by holding a
burning wood splint at the mouth of the test
tube. Do not put the splint down into the test
tube. Record your observations. Decant the
liquid portion of the test tube contents into the
neutralization beaker in the sink discard the
solid into the waste can.
5. Action of Catalyst on Hydrogen Peroxide.
Place ≈5 mL of 3% hydrogen peroxide
solution in an 13 mm X 100 mm test tube.
Obtain regent bottle of manganese(IV) oxide.
Get ready with your glowing splint. Add a
microspoonful of MnO2. If you observe a gas
forming, then test for its identity by
immediately inserting a glowing splint down
into the mouth of the test tube. Record your
Page 2
observations. Rinse the contents of the tube
into the sink.
6. Heating of Magnesium ribbon with oxygen.
Obtain a piece of magnesium ribbon and
handle with crucible tongs. Using a Bunsen
burner, place the magnesium ribbon into the
flame. When the ribbon begins to ignite, do
NOT look directly into the flame. Dispose of
the solid, if any, into the trash. Record your
observations.
7. Action of heat on sodium bicarbonate.
Place ≈5 grams of sodium bicarbonate in a 18
mm X 150 mm test tube. Cap the tube with a
one-hole stopper fitted with a glass tube with
a 90° bend. Clamp the test tube onto a ring
stand at a 45° angle. Fill an 50 mL
Erlenmeyer Flask 2/3 full of lime water and
hold it so that the end of the glass tube is
below the surface of the limewater. Now heat
the sodium bicarbonate tube vigorously with a
Bunsen burner. DO NOT REMOVE THE
BURNER WHILE THE GLASS TUBE IS IN
THE LIMEWATER! Allow the gas to bubble
through the limewater for several minutes and
make observations. Remove the tube of
limewater first, then turn off the burner.
Discard solid residue and spent limewater
down the drain.
Demonstrations to Observe:
8. Action of electricity on water (Electrolysis).
Water can be broken down into its component
elements by passing an electric current
through it. An electrolyte must be added to the
water to allow electricity to flow through the
water. Fill a U-tube three fourths full with 1 M
sulfuric acid solution. Place a stainless steel
electrode in each side of the tube. Attach one
electrode to the positive connector of a power
supply and the other electrode to the negative
connector of the power supply. Cover the
ends of the U-tube with plastic wrap. Turn on
the power supply to provide 10 volts DC.
Make observations of the reaction at several
intervals during a period of 5 minutes. Then
remove the plastic wrap and test the
generated gases with a flaming splint.
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DATA TABLE 1
(40) 5 points for each
Reaction
Fe & CuSO4
Observations
Pb(NO3)2 & KI
Heating
CuSO4•5H2O
Mg & HCl
MnO2 & H2O2
Mg & O2
Heating
NaHCO3
Electrolysis of
H2O
Experiment 3.2
Page 3
Analysis/Conclusions (40)
(24) 1a. Write a balanced equation for each reaction observed, include states.
(16) 1b. Record in the table below the type of reaction represented by each reaction
observed in this experiment.
Reaction
Fe & CuSO4
Balanced Equation
Reaction Type
Pb(NO3)2 & KI
Heating
CuSO4•5H2O
Mg & HCl
MnO2 & H2O2
Mg & O2
Heating
NaHCO3
Electrolysis of
H2O
(10) Discussion:
In a paragraph, discuss the labs objective with specific examples and conclusions that you
determined.
Experiment 3.2
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