Types of Reactions
Chemistry
Learning Objective
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TLW identify and quantify changes that
occur during chemical reactions (TEKS
8)
Agenda
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Review of Basics
Define Types of Chemical Reactions and
Real-World Examples
Examples of the Types of Chemical
Reactions
Group Practice
Individual Practice
Labs
Chemical Reactions –
General Stuff
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Reactants are added together to make
products
Reactants are found on left side of
chemical equation and products are on
the right side
Compounds are formed – substances
made up of two or more elements that
chemically combined (not easily
separated or impossible to return to
original element)
Chemical Reactions –
General Stuff
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Valence electrons and periodic trends
determine how various atoms of elements
react (or don’t react)
Catalysts are “outside agents” that may
be added to speed up reactions or cause
reactions to perform differently under
different conditions (such as varying
temperatures).
– They are not used up in the reaction
Chemical Reactions –
General Stuff
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Don’t forget about the laws of
conservation of mass and energy…
neither can be created nor destroyed
– Reactants are transformed
– Products are formed
– Chemical energy converts to heat, light,
electricity, sound
Chemical Reactions –
General Stuff
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Also – Law of Definite Proportions, which
states in any sample of a chemical compound
the elements are always combined in the same
proportion by mass
H2 O
H=1gx2= 2g
O=
16 g
Total
18 g
H = 2 g / 18 g = 11%
O = 16 g / 18 g = 89%
Chemical Reactions –
General Stuff
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From Dalton’s Laws (remember him?)
Law of Multiple Proportions states
whenever two elements form more than
one compound different masses of one
element that combine with the same mass
of the other element are in the ratio of
small whole number
H2O
H2O2
Chemical Reactions –
General Stuff
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Law of Definite Proportions – describes
composition of one compound
Law of Multiple Proportions – compares
composition of two different compounds
containing same elements
Types of Reactions
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Combination (a.k.a. Synthesis, Addition)
Decomposition
Single Replacement (a.k.a. Single Displacement)
Double Replacement (a.k.a. Double
Displacement)
Combustion
Neutralization
Precipitation
Reduction/Oxidation Reactions (Redox)
Energy Producing – Exothermic, Endothermic,
Light
Combination
(aka Synthesis, Addition)
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Two or more elements or substances combine
to form a new compound.
A + B  AB
Examples –
– Formation of rust
– Air pollutant sulfur dioxide
– Polymerization (plastics)
– Photosynthesis (plants)
Combination
A + B  AB
 Where A and B are elements
and AB is a compound
 Note that only one compound
exists on the RIGHT SIDE…
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Combination
Examples
4Fe(s) + 3O2(g)  2Fe2O3(s)
 S(s) + O2(g)  SOx(g)
 2Na + Cl2  2NaCl
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Teacher Demo – need a better one…..
Decomposition
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A single compound is broken down
to produce two or more smaller
compounds and/or elements.
AB  A + B
Example –
– Water with electricity into
hydrogen and oxygen (electrolysis)
– Baking soda with heat
Decomposition
AB  A + B
 Where AB is a compound and
A & B are elements or other
compounds
 Note that only one compound
exists on the LEFT SIDE…
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Decomposition
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Examples:
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2H2O(l)  2H2(g) + O2(g)
heat
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NaHCO3(s)  2H2(g) + NaCO3
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Teacher demo – baking soda and heat
Single Replacement
(Single Displacement)
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One element replaces (displaces) a similar
element in a compound
Produces heat (is exothermic)
A + BC  AC + B
Example –
– If you place an iron nail into a beaker of
copper (II) chloride you will begin to see
reddish copper forming on the iron.
– Iron replaces (displaces) copper in the
solution and the copper falls out of solution
as a metal
Single Replacement
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A + BC  AC + B
Where A and B are elements and BC
and AC are compounds
Can have more than 2 reactants
and/or products
Example:
2HCl(l) + Zn(s)  ZnCl2(l) + H2(g)
Fe(s) + CuCl2(l)  Cu(s) + FeCl2(l)
Single Replacement
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All single replacement reactions are
exothermic
They give off heat and occur rapidly
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Teacher demo – Zinc plus hydrochloric
acid or iron nail in copper(II)chloride
Double Replacement
(Double Displacement)
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Ions from two compounds in solution exchange
to produce two new compounds
AB + CD  AD + CB
One compound usually forms a precipitate that
settles out of the solution, a gas that bubbles
out, or a molecular compound like water
The other compound formed often remains
dissolved in the solution
Examples –
– Baking soda and vinegar
– Dried fruit
Double Replacement
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AB + CD  AD + CB
Where AB, CD, AD, & CB are all
compounds
Can have more than 2 reactants and/or
products
Examples:
2HCl + 2NaOH 2NaCl + 2H2O
Na2SO3(aq) + 2HCl(aq) 
2NaCl(aq) + H2O(l) + SO2(g)
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Teacher demo – the ever popular baking
soda and vinegar or cleaning pennies
with vinegar using salt as a catalyst
Combustion
Carbon substances combine with oxygen,
releasing large amounts of energy, in the
form of heat, light, etc. Carbon dioxide
and water are also typical products
CxHy + O2  CO2 + H2O
Examples –
– Natural gas to heat a house
– Hydrogen powered cars
General Formula
CxHy + O2  CO2 + H2O
hydrocarbon oxygen
carbon
dioxide
water
Examples CH4 + 2O2 CO2 + 2H2O
2H2(g) + O2(g)  2H2O(l)
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Teacher demo – lighting a match
Neutralization
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Double Replacement Reaction where wn acid
and a base react to form water and a salt
General formula
HA + BOH  H2O + BA
acid
base
water
salt
Examples –
HCl(aq) + NaOH(s)  H2O(l) + NaCl(s)
H2SO4(aq) + Ca(OH)2(aq)  H2O(l) + CaSO4(s)
Precipitation
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When solutions are saturated, adding
additional ions will cause a precipitate to form
Solid – usually sinks to bottom, but can float
Solubility product (Ksp) can be used to predict
formation of precipitates
– If ion-product concentration > Ksp then a precipitate
will form
– If ion-product concentration < Ksp then a precipitate
will not form
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Teacher demo – baking soda and
vinegar… again (how boring)
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Practice Worksheet – Identify 5 basic
reactions
Reduction/Oxidation
Discovery Video - Electrochemistry
Reduction/Oxidation Reactions
A. Reaction in which electrons are
transferred
B. Commonly called the redox
reaction
C. One element is reduced – it gains
electrons
One element is oxidized – it loses
electrons
Redox reactions have radicals
fragments of molecules with
at least one electron for
bonding
Ex. of radicals = Styrofoam
Example of redox reaction
Rust = iron reacts with oxygen
Fe2O3
Fe loses 3 electrons
O gains 2 electrons
Rules for Assigning
Oxidation Numbers
Rule 1
The oxidation number of
any uncombined element
is 0
Example:
The oxidation number of
Na (s) is 0.
Rule 2
The oxidation number of
a monatomic ion equals
the charge on the ion.
Example:
The oxidation number
of Cl is -1.
Rule 3
The more electronegative
element in a binary
compound is assigned the
number equal to the charge it
would have if it were an ion.
Example:
The oxidation number
of O in NO is -2.
Rule 4
The oxidation number of
fluorine in a compound is
always -1.
Example:
The oxidation number of
F in LiF is -1.
Rule 5
Oxygen has an oxidation
number of -2 unless it is
combined with F, when it is
+2, or it is in a peroxide, such
as H2O2, when it is -1.
Example:
The oxidation number
of O in NO2 is -2.
Rule 6
The oxidation state of
hydrogen in most of its
compounds is +1 unless it is
combined with a metal, in
which case it is -1.
Example:
The oxidation number
of H in LiH is -1.
Rule 7
In compounds, Group 1 and
2 elements and aluminum
have oxidation numbers of
+1, +2, and +3, respectively.
Example:
The oxidation number of Ca in
CaCO3 is +2.
Rule 8
The sum of the oxidation
numbers of all atoms in
a neutral compound is 0.
Example:
The oxidation number of
C in CCO3 is +4.
Rule 9
The sum of the oxidation
numbers of all atoms in a
polyatomic ion equals the
charge of the ion.
Example:
The oxidation number of P in
H2PO- 4 is +5.
Exothermic Reactions
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In many reactions, less energy is required to
break the bonds in the reactants than is
released when bonds form to make new
products
In these reactions some type of heat or light is
released and they are called exothermic
Exothermic reactions can be detected by a rise
in temperature
Exothermic Reactions
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What are examples of exothermic
reactions you are familiar with?
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Demonstration
Endothermic Reactions
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Sometimes more energy is required to
break bonds in the reactants than is
released to form new products
The are called endothermic reactions
You can detect these reactions by a
decrease in temperature
Endothermic Reactions
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What are examples of endothermic
reactions you are familiar with?
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Demonstration
Group Practice ~ Name Those
Reactions
A Group Activity
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Types of Chemical Reactions – Sorting
Mats link
Individual Practice
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Identifying Types of Reactions
Worksheet link
Crossword Puzzle
Looking Ahead
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Labs –
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Conservation of Mass
Types of Chemical Reactions
Empirical Formula Determination
Predicting the Amount of Product in a Reaction
Identifying Relationships between Reactants and
Products in a Reaction
Predicting the Products of a Reaction
Precipitation Reactions
Energetic Reactions – exothermic and endothermic
experiments
Qualitative and Quantitative Analysis
More on calculating definite proportions and
multiple proportions