General Chemistry
Unit 11

5 Reaction Types
o Synthesis reactions
o Decomposition reactions
o Single replacement/displacement reactions
 Activity series
o Double displacement/replacement
 Solubility rules
o Combustion reactions
.
We are looking for:
1a. Identify the types of reactions based upon the constituent elements.
(Synthesis, Decomposition, Single Replacement, Double Replacement, and Combustion)
1b. Given the reactants, predict the products in a chemical equation.
1c. Determine whether or not a replacement reaction will occur.
1
To react or not to react?
THAT is the question!
Chemical changes are a result of chemical reactions. All chemical reactions involve a change in substances and a change
in energy. Neither matter or energy is created or destroyed in a chemical reaction---only changed. There are so many
chemical reactions that it is helpful to classify them into 5 general types which include the following:
SYNTHESIS REACTION
In a synthesis reaction two or more simple substances combine to form a more complex substance. Two or more
reactants yielding one product is another way to identify a synthesis reaction.
For example, simple hydrogen gas combined with simple oxygen gas can produce a more complex substance----water!
The chemical equation for this synthesis reaction looks like:
reactant + reactant -------> product
To visualize a synthesis reaction look at the following cartoon:
In the cartoon, the skinny bird (reactant) and the worm (reactant) combine to make one product, a fat bird.
DECOMPOSITION REACTION
In a decomposition reaction a more complex substance breaks down into its more simple parts. One reactant
yields 2 or more products. Basically, synthesis and decomposition reactions are opposites.
For example, water can be broken down into hydrogen gas and oxygen gas. The chemical equation for this
decomposition reaction looks like:
reactant -------> product + product
2
To visualize a decomposition reaction look at the following cartoon:
In this cartoon the egg (the reactant), which contained the turtle at one time, now has opened and the turtle
(product) and egg shell (product) are now two separate substances.
SINGLE REPLACEMENT REACTION
In a single replacement reaction a single uncombined element replaces another in a compound. Two reactants
yield two products. For example when zinc combines with hydrochloric acid, the zinc replaces hydrogen. The
chemical equation for this single replacement reaction looks like:
reactant + reactant ---------> product + product
To visualize a single replacement reaction look at the following cartoon:
Notice, the guy in the gray shirt steals the date of the other guy. So, a part of one of the reactants trades places
and is in a different place among the products.
3
DOUBLE REPLACEMENT REACTION
In a double replacement reaction parts of two compounds switch places to form two new compounds. Two
reactants yield two products. For example when silver nitrate combines with sodium chloride, two new
compounds--silver chloride and sodium nitrate are formed because the sodium and silver switched places. The
chemical equation for this double replacement reaction looks like:
reactant + reactant ---------> product + product
To visualize a double replacement reaction look at the following cartoon:
COMBUSTION REACTION
A combustion reaction occurs when a compound containing carbon combines with the oxygen gas in the air. This
process is commonly called burning. The products are always carbon dioxide and water.
Here’s the equation that represents the burning of propane:
C3H8 + O2
CO2 + H2O
ENERGY OF CHEMICAL REACTIONS
Chemical reactions always involve a change in energy. Energy is neither created or destroyed. Energy is
absorbed or released in chemical reactions. Chemical reactions can be described as endothermic or exothermic
reactions.
Endothermic Reactions
Chemical reactions in which energy is absorbed are endothermic. Energy is required for the reaction to occur.
The energy absorbed is often heat energy or electrical energy. Adding electrical energy to metal oxides can
separate them into the pure metal and oxygen. Adding electrical energy to sodium chloride can cause the table
salt to break into its original sodium and chlorine parts.
Exothermic Reactions
Chemical reactions in which energy is released are exothermic. The energy that is released was originally stored
in the chemical bonds of the reactants. Often the heat given off causes the product(s) to feel hot. Any reaction
that involves combustion (burning) is an exothermic chemical reaction.
4
Types of Chemical Reactions
Across
2. starting materials
9. anion trades one cation for another
Down
1. new materials made
3. 2 cations and 2 anions switch partners
4. arrow means
5. has only one reactant
6. products are carbon dioxide and water
7. 2 small pieces make 1 new bigger piece
8. reaction where energy is absorbed
10. reaction where heat is made
5
Synthesis Reactions
+

__ elements or small compounds reacted together to make
____________________
Examples:
Joining elements:
__
+
__

__
What is the oxidation number of Iron
if sulfur has a -2 charge? ____
__Na + __Cl2  __NaCl
Joining compounds:
___ CO2 + ___ H2O  ___ C6H12O6 + ___O2
*** Synthesis reactions have one main purpose:
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Synthesis Reactions
Predict the products of these reactions and then balance the equations.
1. ___Mg + ___O2 → ___
2. ___P4O10 + ___H2O
3. ___Fe (III)
→ ___H3PO4
+ ___ I2 → ___
4. ___H2 + ___Cl2 → ___
5. Zinc + Sulfur →
6. Lead (IV) + Oxygen →
7. Potassium + Fluorine →
8. Hydrogen + Oxygen →
7
Synthesis:
In this activity, you will be determining the mass of the reactants before a chemical reaction and the
mass of the products after the reaction.
Materials:
4) crucible
5) crucible tongs
6) ring stand with clay
triangle
1) balance
2) Bunsen burner
3) Mg ribbon
Procedure:
1) Determine the mass of the empty crucible and record in table 1.
2) Obtain a 6 in strip of Mg ribbon. Cut it into about 12 pieces and put the pieces into the crucible
and determine the mass. Record in table 1.
3) Place the crucible on the clay triangle and slowly heat it with a “soft” blue flame for a minute.
4) Increase the heat gradually by adjusting the burner’s flame until the crucible is at the tip of the
inner cone.
5) Once the Mg begins to react, wait about 1 minute and then turn off the burner.
REMEMBER: DO NOT LOOK DIRECTLY AT THE LIGHT!!!
6) Allow the crucible to cool on the ring stand for 15-20 min. Then determine the mass of the
product by weighing the crucible + product and subtracting the mass of the crucible. Record in
table 1.
Mass of Crucible
Mass of reactant (Mg)
Mass of product (?)
Analysis:
1) Compare the mass of the reactant to the mass of the product by determining the % recovery:
% recovery = (mass of product/mass of reactant) x 100
2) Write the balanced equation for the reaction that occurred. Be sure to include any inputs and
outputs such as heat, chemical catalysts, energy, light, etc. Hint: Mg combined with oxygen.
8
Decomposition Reactions
→
+
reactant
(
)
forms
or
(
)
For decomposition reactions to occur –
need energy:
●
●
●
●
9
Some compounds decompose readily, if formed in
a reaction:
H2CO3 = Carbonic Acid
H2CO3(aq) →
(l) +
(g)
H2SO3 = Sulfurous Acid
H2SO3(aq) →
(l) +
(g)
Verifying your products:
 If product is H2
o Use burning splint
o Will hear a “
”
 If product is O2
o Use glowing splint (blow it out)
o Will
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Decomposition of Water:
___H2O
→ ___H2 + ___O2
Gas = ____
Gas = ____
Proof:
Proof:
11
Decomposition of Hydrogen Peroxide
Decomposition:
In this activity, you will be determining the products of the decomposition of hydrogen peroxide.
Materials:
1) glass jar
2) pie plate
3) 125 ml Hydrogen peroxide
4) 100 ml graduated cylinder)
6) 100 ml warm water
5) Food coloring
10) stirring rod
7) 250 ml beaker
8) 7g yeast
9) weigh boat
11) wood splints
Procedure:
Group 1:
1. Place glass jar in center of pie plate.
2. Add 125 ml of hydrogen peroxide to the glass jar.
3. Add 4 drops of food coloring to glass jar – your choice!
4. Place pie plate with glass jar in center of lab station
5. Wait for further instructions
Group 2:
1. Put 7 grams of yeast into 250 ml beaker
2. Add 100 mL warm water to same 250 ml beaker
3. Using stirring rod, stir yeast and warm water for 3-5 minutes
4. Wait for further instructions
Analysis:
Write the balanced equation for the reaction that occurred. Be sure to include any inputs and outputs
such as heat, chemical catalysts, energy, light, etc. Hint: The yeast remains unchanged and one of the
products is water.
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Decomposition Reactions
Determine the coefficients!
1. ____Na2CO3
→
____ Na2O + ____ CO2
2. ____ HgO → ____ Hg + ____O2
3. ____ NaCl → ____Na + ____ Cl2
4. ____ NH4NO3 → ____ N2O + ____ H2O
5. ____ KClO3 → ____ KCl + ____ O2
6. Silver (I) Oxide decomposes into Silver and Oxygen
7. Iron (III) Oxide decomposes into Iron and Oxygen
8. Calcium Carbonate decomposes into Calcium Oxide and Carbon Dioxide
Bonus:
____(NH4)2Cr2O7 → ___ NH3 + ___H2O + ___Cr2O3 + ___O2
13
Single Replacement Reactions
** Single Displacement**
+

+
A __________________ “A” displaces or switches
places with a ___________________ “B”
Example:
1. Fe + CuCl2  FeCl2 + Cu
2. Cu + AgNO3  Ag + Cu(NO3)2
3. Ca + H2O 
If A is ___________ than B, the reaction takes place!
If A is _____________ than B, nothing happens!!
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Single Replacement Activity
1. Use a spot plate to perform the following investigation.
2. Each kind of metal will be tested with 5 different solutions.
 Reactions will occur when the free metal is more reactive than the
metal in the solution.
 No reaction will occur if the free metal is less reactive than the
metal in the solution.
3. Place 1 piece of metal in each well. Add enough solution to
completely cover the metal (10 to 20 drops).
4. Watch carefully…. Be Patient!!!!
 If a reaction occurs, place a
in that box on the table and
write the sign that indicates that there is a reaction taking place
(Color, Gas, Precipitate).
 If a reaction does not occur – place an X in that square.
Zn(NO3)2 Pb(NO3)2
MgSO4
CuSO4
Fe(NO3)3
CaCl2
Zn
Pb
Mg
Cu
Fe
Ca
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One last test,
take a piece of copper (Cu) and test it with AgNO3 solution.
 Do you see a reaction? ________________
 What does this result mean? _____________________
Conclusion:
Below – Rank the metals from this activity based on their reactivity. Include
silver (Ag) in the rankings!
Most reactive metal







Least reactive metal
Clean-up:
Dump the liquids and reacted metals on a paper towel (or two) and throw in
the trash! Rinse the spot plate with water (Use a test tube brush to clean
out the spots, if necessary) then place it upside down on some paper towels
to dry. Thanks!!
16
Using the activity chart provided, predict whether or not the following
reactions will take place. For the reactions that will occur, predict the
products and then balance the reaction.
= Go
= No Go
_____
1. Al + Fe2O3 
_____
2. Pb + MgSO4 
(Pb charge = +2)
_____
3. Zn + FeCl3 
(Zn charge = +2)
_____
4. Fe + CuCl2 
(Fe charge = +3)
_____
5. Ag + CuSO4 
(Ag charge = +1)
_____
6. Au + AgBr 
(Au charge = +1)
_____
7. Cr + NiI2 
(Cr charge = +2)
_____
8. K + MgSO4 
_____
9. Zn + MgCl2 
(Zn charge = +2)
_____
10. Na + CaSO4 
17
Activity Series
Metals
Lithium,Li
Potassium, K
Calcium, Ca
Sodium, Na
Magnesium, Mg
Aluminum, Al
Zinc, Zn
Chromium, Cr
Iron, Fe
Nickel, Ni
Tin, Sn
Lead, Pb
Hydrogen, H
Copper, Cu
Mercury, Hg
Silver, Ag
Platinum, Pt
Gold, Au
Decreasing Activity
Halogens
fluorine, F
chlorine, Cl
bromine, Br
iodine, I
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More Single Replacement practice:
1. ___Al + ___CuCl2
2. ___ Br2 + ___CaI2
3. ___ Zn + ___H2SO4
4. ___ Br2 + ___CaI2
5. ___ Al + ___Pb(NO3)2
6. ___ Cl2 + ___KI
7. ___ Ag + ___KNO3
8. ___ F2 + ___NaI
19
Double Replacement
(or Double Displacement)
AB + CD → AD + CB
Both pairs change partners –
 Always write positive ion (cation) first
For Products:
 Formulas can and will change
 Look up charges for each ion
 Do 1 to 1 or criss cross
Once formulas are adjusted:
 Take inventory of reactants and products
 Balance equation
Example:
Potassium Iodide + Lead (II) Nitrate →
K
I
+
Pb
(NO3)
→
20
A double replacement reaction will occur IF:
 Water forms
 A gas forms
o H2CO3 immediately breaks down
 It forms CO2 + H2O
 CO2 is a gas
o Other gases: H2, O2, N2, Cl2, F2
 A precipitate forms (Use solubility table)
o If a compound is soluble – it is not a sign that the
reaction will go).
o A precipitate is insoluble – it is evidence that the
reaction will go.
21
Ion Solubility Rules
*For Double Replacement/Displacement Reactions*
1. All compounds containing alkali metals (Li+, Na+, K+, Rb+, Cs+) or ammonium
(NH4+) are soluble.
2. All nitrates (NO3-), acetates (C2H3O2-), and chlorates (ClO3-) are soluble.
3. All metal ions combined with the halogens (Cl-, Br-, I-, F-) are soluble, except
for Hg, Ag, and Pb.
4. All sulfates (SO42-) are soluble, except for Ca, Ba, Sr, and Hg, Ag, and Pb.
5. Except for rule #1, all carbonate (CO32-), chromates (CrO42-), hydroxides (OH-),
oxides (O2-), phosphates (PO43-) and sulfides (S2-) are insoluble.
22
Predicting Products and Solubility Rules Practice:
CaCl2
Pb(NO3)2
AgC2H3O2
FeF2
Na2CO3
Rb3PO4
K2SO4
NH4Br
Li2S
23
Write the complete chemical equation and balance it for each of the six reactions.
1. Sodium Carbonate +
Hydrogen Chloride → Product 1 and Product 2
Using the Solubility Chart:
Product 1 = __________
Product 2 = __________
Is it soluble? Yes or No
Is it soluble? Yes or No
If either Product 1 or 2 is not soluble, the reaction will take place!
Mix 2 milliliters of each reactant together; make observations:
Did the reaction really take place? What chemical signs were present to indicate that a
reaction took place?
____________________________________________________________
2. Hydrogen Chloride +
Sodium Hydroxide → Product 1 and Product 2
Using the Solubility Chart:
Product 1 = __________
Product 2 = __________
Is it soluble? Yes or No
Is it soluble? Yes or No
If either Product 1 or 2 is not soluble, the reaction will take place!
Mix 2 milliliters of each reactant together; make observations:
Did the reaction really take place? What chemical signs were present to indicate that a
reaction took place?
____________________________________________________________
24
3. Barium Nitrate +
Sodium Sulfate → Product 1 and Product 2
Using the Solubility Chart:
Product 1 = __________
Product 2 = __________
Is it soluble? Yes or No
Is it soluble? Yes or No
If either Product 1 or 2 is not soluble, the reaction will take place!
Mix 2 milliliters of each reactant together; make observations:
Did the reaction really take place? What chemical signs were present to indicate that a
reaction took place?
____________________________________________________________
4. Lead (II) Nitrate +
Sodium Chloride → Product 1 and Product 2
Using the Solubility Chart:
Product 1 = __________
Product 2 = __________
Is it soluble? Yes or No
Is it soluble? Yes or No
If either Product 1 or 2 is not soluble, the reaction will take place!
Mix 2 milliliters of each reactant together; make observations:
Did the reaction really take place? What chemical signs were present to indicate that a
reaction took place?
____________________________________________________________
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5. Ammonium Chloride +
Sodium Hydroxide → Product 1 and Product 2
Using the Solubility Chart:
Product 1 = __________
Product 2 = __________
Is it soluble? Yes or No
Is it soluble? Yes or No
If either Product 1 or 2 is not soluble, the reaction will take place!
Mix 2 milliliters of each reactant together; make observations:
Did the reaction really take place? What chemical signs were present to indicate that a
reaction took place?
____________________________________________________________
6. Lead (II) Nitrate +
Potassium Chromate → Product 1 and Product 2
Using the Solubility Chart:
Product 1 = __________
Product 2 = __________
Is it soluble? Yes or No
Is it soluble? Yes or No
If either Product 1 or 2 is not soluble, the reaction will take place!
Mix 2 milliliters of each reactant together; make observations:
Did the reaction really take place? What chemical signs were present to indicate that a
reaction took place?
____________________________________________________________
26
Double Replacement Reactions
Predict the products. Predict if these reactions will go to completion using the
solubility rules. Indicate whether each product is soluble (aq) or insoluble (s).
1. ___ NaOH(aq) + ___ CaBr2

(aq)
Will this reaction occur? _____
2. ___ Pb(NO3)2
(aq)
+ ___ HCl
(aq)

Will this reaction occur? _____
3. ___ Na2(CO3)
(aq)
+ ___ KF
(aq)

Will this reaction occur? _____
4. ___ Ag(NO3)
(aq)
+ ___ Cu(SO4)
(aq)

Will this reaction occur? _____
5. ___ LiF
(aq)
+ ___ NiCl2
(aq)

Will this reaction occur? _____
27
Combustion Reactions
+

+
**One reactant needs _________________ **
**The other _________________________**
The products are always ______+ ______.
___________________ are always exothermic
(They give off _____________________!)
Examples:
 ___CH4 + ___ O2  ___CO2 + ___H2O
 ___C4H10 + O2  ___CO2 + ___H2O
The CxHy reactant can also contain _________:
(CxHyOz)
2CH3OH + 3O2  2CO2 + 4H2O
28
Combustion Reactions
Complete the Reactions and Balance!
1. ___CH4 + ___O2 
2.
___C3H8 + ___O2 
3.
___C8H18 + ___O2 
4.
___C6H12O6 + ___O2 
5.
___C6H6 + ___O2 
6.
___C2H6 + ___O2 
7.
___CH3OH + ___O2 
8.
___C3H7OH + ___O2 
9.
___C8H17OH + ___O2 
10 ___C6H5OH + ___O2 
29
Classification of Chemical Reactions
A
+
B

AB 
A + BC

AB
Synthesis
A + B
Decomposition
B + AC
Single Replacement
AB + CD  AD + CB
Double Replacement
CxHy + O2  CO2 + H2O
Combustion
30
??? WHAT KIND OF REACTION ???
1. Ca + O2 
2. HgO 
3. Cd + HCl 
4. MnSO4  MnO + SO3
5. Al + Cl2 
6. FeCl2 + Na3PO4 
7. Mg + CuSO4

8. NaNO3  NaNO2 + O2
9. Mg + N2 
10.
O2 + C2H6 
31
Types of Reactions Worksheet
For each reaction: balance and predict reaction type .
1. ___NaBr + ___H3PO4 → ___Na3PO4 + ___HBr
Type of Reaction: __________________________
2. ___Mg + ___Cr2O3 → ___Cr + ___MgO
Type of Reaction: __________________________
3. ___Fe + ___Cl2 → ___FeCl3
Type of Reaction: __________________________
4. ___CaS → ___Ca + ___S8
Type of Reaction: __________________________
5. ___Pb + ___HCl → ___PbCl2 + ___H2
Type of Reaction: __________________________
32
6. ___H2SO4 + ___NH4OH → ___H2O + ___(NH4)2SO4
Type of Reaction: __________________________
7. ___HgO → ___Hg + ___O2
Type of Reaction: __________________________
8. ___Rb + ___P4 → ___Rb3P
Type of Reaction: __________________________
9. ___C6H14 + ___O2 → ___CO2 + ___H2O
Type of Reaction: __________________________
33
Fun with Predicting Reaction Products
1)
___Ag2SO4 + ____ NaNO3 
2) ___NaI + ___ CaSO4 
3) ___HNO3 + ___ Ca(OH)2 
4) ___ CaCO3 
5) ___AlCl3 + ___ (NH4)PO4 
6) ___Pb + ___ Fe(NO3)3 
7) ___C3H6 + ___ O2 
34
8) ___Na + ___ CaSO4 
9)
____Na + ____O2 
10)
____C4H10 + ____O2 
11)
____BrF3
12)
____C8H18 + ____O2 
13)
____Sb + ____I2
14)
____Al2O3 


35