INTRODUCTION TO
CHEMICAL REACTIONS
Text 3.1: Page 108-113
Learning Goals

By the end of this class, the students will be
able to:
 Identify
chemical formulas and their parts
 Describe evidence for chemical change
 Describe chemical change in terms of molecular theory
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Hamilton, ON

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
July 9-12, 1997
400 TONS of plastic caught
fire at a manufacturing
plant
Many people were exposed
to benzene, hydrochloric
acid and other hazardous
chemicals
CAUSE: an improperly
controlled chemical reaction
How do we Define Chemical Reactions?
Remember our Balancing?
1.
2.
3.
4.
Balance Metals
Balance Non- Metals
Balance Oxygen
Balance Hydrogen
Catalysts

Not used up in the reaction just speed it up
 Are
consumed but regenerated
 Align reactants so they can hit in a favourable way

Written above the arrow because not a reactant
or product
Example
Evidence of Chemical Change

A chemical change is
the transformation of
one or more
substances into
different substances
with different
properties
Hints of Chemical Change
1.
Change in colour
Hints of Chemical Change
2.
Production of a Gas
Hints of Chemical Change
3.
Formation of a Precipitate
Hints of Chemical Change
4.
Production or Absorption of Heat
Hints of Chemical Change
5.
Production or Light
Why Do Things React?

Kinetic molecular theory outlines that molecules
are always in motion and will always have
random collisions
 Increased
temperature and pressure can increase
speed of hits or number of collisions

Collision reaction theory outlines that these
hits will allow for chemical reactions and change
when the right number and position of reactants
hit
Synthesis Reactions
A + B → AB
Chemical reactions that involve
two or more substances coming
together to form a more
complex compound
 Like putting together a puzzle

Examples: Acid Precipitation


Pollution generally will give
off CO2 as a waste product
This enters our atmosphere
and mixes with water to
produce Carbonic acid
 This
causes almost all
precipitation to now be
slightly acidic
CO2 (g) + H2O (l) → H2CO3 (aq)
Examples: The Haber Process

Used to Synthesize Ammonia
for use in fertilizers
 Also
makes use of enriched
iron or ruthenium catalysts

Important because prior to its
discovery very hard to
produce ammonia
commercially
N2 + 3H2 → 2NH3
Example: Synthesis of Manganese
Heptoxide
Types of Synthesis

Type 1: Two Elements forming binary compound
 Ex:
Nitrogen and oxygen coming together to form
Nitrogen monoxide
 This
reaction happens when you burn gasoline at a high
temperature
 Can form nitric acid when combined with water which can
also contribute to acid rain
2N2(g) + O2 (g) → 2NO2 (g)
Types of Synthesis

Type 1: Two Elements forming binary compound
 Ex:
Nitrogen and oxygen coming together to form
Nitrogen monoxide
 This
retraction happens when you burn gasoline at a high
temperature
 Can form nitric acid when combined with water which can
also contribute to acid rain
2N2(g) + O2 (g) → 2NO2 (g)
Types of Synthesis

Type 2: An Element and a Compound producing a
new compound
 Potassium chloride can be mixed with oxygen gas
to produce potassium chlorate
 KClO3 has many practical uses including being a
good disinfectant and used in the production of
fireworks
KCl + O2 → KClO3
Types of Synthesis

Type 3: Two compounds forming a new compound
 Ex.
A non-metal oxide and water which forms an acid
P2O5 + H2O → H3PO4
 Ex.
A metal oxide reacting with water to produce a
base
Na2O + H2O → NaOH
Demo!
Decompositions
AB → A + B
Chemical reaction in which a
substance is broken down into
two or more simple substances
 Generally why so explosive



i.e. TNT is a decomposition
Like breaking apart a puzzle
Examples: NO2 Decomposition



UV from sun can decompose
NO2 to NO and O
The very reactive O can
combine with other chemical
to produce chemicals very
bad for you
They may even cause
breathing disorders
Examples: Hydrazine Fuel

Hydrazine fuel
 Used
in the Phoenix Mars
Lander in its thruster rockets to
fire pulses of gas
 Decomposes quickly and
produces a large volume of hot
gas from a small amount of
fuel so ideal
3N2H4 (l) → 4NH3 (g) + N2 (g)
Example: Air Bags
2NaN3 (s) —> 3N2 (g) + 2 Na (s)
Types of Decomposition

Type 1: Binary compound decomposing into
elements
 Ex:
Electrolysis is a process that uses electrical energy to
break down the chemical bonds resulting in a
decomposition
 This
is how hydrogen gas is produced from water
2H20 (l) → 2H2 (g) + O2 (g)
Types of Decomposition

Type 2: Metal nitrates decomposing into a metal
nitrite and oxygen gas
 Generally
compounds made of more than 2 elements
will not break down into their individual elements
 Ex: Decomposition of sodium nitrate results in sodium
nitrite
 This
is an explosive
2NaNO3 (s) → 2NaNO2 (s) + O2 (g)
Types of Decomposition

Type 3: A metal carbonate decomposing into a
metal oxide and carbon dioxide
 Ex:
Decomposition of calcium carbonate to make
calcium oxide
 An
important ingredient in cement
CaCO3 (s) → CaO (s) + CO2 (g)
Types of Decomposition

Type 4: A metal hydroxide decomposition into a
metal oxide and water
 Ex:
calcium hydroxide into calcium oxide and water
 Calcium
oxide is also known as quicklime
 Used in mortar
Ca(OH)2 (s) → CaO (s) + H2O (g)
Combustion Demo!
What is Combustion?



Commonly known as burning
Involves oxygen combining with another substance in
the presence of heat and releases energy in the form
of heat and light
Need to have a fuel, oxygen and heat to proceed

Common fuels: hydrocarbons which can be completely or
incompletely combusted
AB + O → AO + BO
What is Combustion?





Can we Predict the Products of Combustion RXNs?
C2H4 + O2 → CO2 + H2O
C2H2 + O2 → CO2 + H2O
C6H6 + O2 → CO2 + H2O
Note: These are only skeleton equations
Types of Combustion

Complete combustion
hydrocarbons react with sufficient
oxygen to produce carbon
dioxide and water vapour
 Flame
appears blue
 What we predicted above

Note: Other things can combust,
H2, S and Mg but we focused on
the combustion of hydrocarbons
Types of Combustion

Incomplete combustion of
hydrocarbons involves a reaction with
insufficient oxygen
 Produces

carbon dioxide, toxic carbon
monoxide, water vapour and
elemental carbon
 Elemental carbon also known as soot
 CO toxic because binds into your blood
more easily than O2 so you can
suffocate
If incomplete combustion flame will
appear yellow/orange
Combustion of Acetylene Gas
Experiment!
Single Displacement Reactions

Like a dosey-doe dance
A
lone metal replaces a metal in
a compound
 Or
a lone non-metal replaces a nonmetal in a compound

Generally in aqueous solutions
AB + C → CB + A
AB + C → AC + B
EX: Metal Exactions

Used to extract metals found
in nature as metal ores
 i.e.

Copper Ores → Copper
We do this by reacting the
metal ore containing the metal
we want with a more reactive
and less desirable metal
Fe (s) + CuSO4(aq) → FeSO4 (aq) + Cu(s)
EX: Galvanizing

Many time metals are coated with
a reactive metal to create a
protective coating
 i.e.

on many metal fences
The reactive metal coating with
quickly transform into a metal
oxide which acts as a protective
layer to the metal beneath
Type 1: Metal Displacing in an Ionic

A metal displacing another
metal from an ionic compound
 Most
common
 The lone metal must be more
reactive than the metal in the
compound
Cu(s) + 2AgNO3(aq) →Cu(NO3)2 +2 Ag(s)
Activity Series


Can see if a metal will
replace another metal
based on Activity Series
 Only will displace if
MORE reactive
Note: highly reactive metals
are very useful in many
situations but they also can
be very dangerous because
of their reactivity
Type 2: Hydrogen Displacing in Acid/Water

A metal displacing hydrogen from an
acid or water
 Although
hydrogen is not a metal,
because it can produce a cation with a
+1 charge it can act like a metal and
thus is included
 H2 is produced when H is replaced
Mg(s) + 2HCl(aq) →MgCl2 (aq) + H2 (g)
Type 3: Non-Metal Displacing in an Ionic

Non-metal displacing another
non-metal from an ionic
compound
 Generally
involves a halogen
replacing another non-metal
 Has a unique activity series
Cl2 (g) + 2NaBr (aq) → 2NaCl (aq) + Br2 (l)
Double Displacement Reactions

Like a DOUBLE dosey-doe
dance
A
metal in compound replaces a
metal in a compound
 AND
a non-metal in compound
replaces a non-metal in a compound

Generally in aqueous solutions
AB + CD → AD + CB
EX: X-Ray Imaging


X rays are useful to image hard
things in the body like bone
To observe soft tissue you may
have to drink a BaSO4 solution
 These
particles block x-rays and
allow imaging of soft tissue
 This chemical is produced by a
double displacement reaction
BaS + H2SO4 → BaSO4 + H2S
EX: Duodenum Neutralization


Hydrochloric acid is
produced in the stomach and
requires neutralization by
bile and pancreatic fluids
located in the duodenum
Makes it so acid from
stomach does not burn
through the tissue that makes
up your intestines
HCl + NaOH → NaCl + H2O
Type 1: 2 Aqueous Salts forming a Solid

Also called a
precipitate
 An
insoluble solid
formed and floating in
solution

Have to use a
solubility chart to
determine when a
precipitate is formed
Examples

Sodium hydroxide and copper sulphate
CuSO4(aq) + 2NaOH(aq) →

Sodium Hydroxide and Iron (III) chloride
FeCl3(aq) + 3NaOH(aq) →

Sodium Hydroxide and Nickel Chloride
NiCl2(aq) + 2NaOH(aq) →
Examples

Sodium hydroxide and copper sulphate
CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq)

Sodium Hydroxide and Iron (III) chloride
FeCl3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaCl(aq)

Sodium Hydroxide and Nickel Chloride
NiCl2(aq) + 2NaOH(aq) → Ni(OH)2(s) + 2NaCl(aq)
Type 2: Reactions that Form a Gas

Common gases formed include CO2 and NH3
 CO2
and water formed when an acid reacts with a
molecule with carbonate ions
2HCl(aq) + CaCO3(aq) → CaCl2(aq) + CO2(g) + H2O(l)
 NH3
and water is produced when a reactant with
ammonium ions reacts with something with hydroxide
ions
NH4+(aq) + NaOH(s) → Na+(aq) + NH3(g) + H2O (l)
Type 3: Reactions that Form Water

Can be when an acid and a
base are mixed
 i.e.
an acid (with a n H to
donate) reacts with a base
(with OH present) to produce
water (H2O)
 Special
name called a
neutralization
HCl + NaOH → NaCl + H2O
Need More Practise?

Another Online Quiz Here:
http://www.quia.com/cb/40304.html?AP_rand=569
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Reference