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Ch 4 Chemical reactions
Ch 4 Chemical Reactions
Big Idea 3: Changes in matter involve the
rearrangement and/or reorganization of atoms
and/or the transfer of electrons
Ch 4 Chemical Reactions
Enduring understanding 3.A:
Chemical changes are represented by a balanced
chemical equation that identifies the ratios with
which reactants react and products form.
Essential knowledge 3.A.1:
A chemical change may be represented by a
molecular, ionic, or net ionic equation.
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Ch 4 Chemical Reactions
Enduring understanding 3.B:
Chemical reactions can be classified by considering
what the reactants are, what the products are, or
how they change from one into the other. Classes
of chemical reactions include synthesis,
decomposition, acid-base, and oxidation-reduction
reactions.
Ch 4 Chemical Reactions
Sec 4.3 Precipitation Reactions
Predict products of a metathesis reaction
based upon the reactants
Sec 4.1 Ionic Theory of Solutions and Solubility
Rules
Apply solubility rules to predict solubility of
compounds in water
Sec 4.2 Molecular and Ionic
Equations Objectives
Write chemical equations for a reaction as if
all the substances were molecular
Break apart molecular equations into a
complete ionic equation based upon the
definition of strong electrolyte
Identify spectator ions in a complete ionic
equation
Evaluate a complete ionic equation, canceling
out spectator ions to determine the net ionic
equation of a chemical reaction
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Precipitation reactions
Double replacement reaction
When aqueous solutions of ionic
compounds are reacted together a solid
forms.
A solid that forms from reacted
solutions is a precipitate
If you’re not a part of the solution, your
part of the precipitate
Precipitation reactions
3NaOH
(aq) +
FeCl3 (aq) →3NaCl (aq) + Fe(OH) 3 (s)
is really
3Na+(aq)+3OH- (aq) +Fe+3(aq)+3Cl-(aq)→3Na+(aq)+3Cl-(aq)+ Fe(OH)3 (s)
So all that really happens is
3OH- (aq) + Fe+3 (aq) → Fe(OH)3 (s)
Precipitation reaction
We can predict the products
In a double displacement reaction, the
anion and cation switch partners
EXAMPLES
AgNO3(aq) + KCl(aq) →
Zn(NO3)2(aq) + BaCr2O7(aq) →
CdCl2(aq) + Na2S(aq) →
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Precipitations Reactions
Only happen if one of the products is
insoluble or a pure substance (more on
that later)
Otherwise all the ions stay in solution- no
reaction.
Need to memorize the rules for solubility
(pg 128 old book, pg 129 new book)
Solubility Rules
(aq)
•
•
•
Group IA and NH4+ ions are soluble
Acetates and nitrates are soluble
Most Group VIIA are soluble
• except Ag+, Pb+2, Hg+2 and Hg2+2
•
Most sulfates are soluble
• except Pb+2, Ba+2, Hg+2, Sr+2, Ag+1and Ca+2
Solubility Rules
(ppt)
• Most carbonates are insoluble
• except Group IA and Ammonium
• Most phosphates are insoluble
• except Group IA and Ammonium
• Most sulfides are insoluble
• except Group IA and Ammonium
• Most Hydroxides are insoluble
• except Group IA, Ca+2, Sr+2 , Ba+2
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Precipitation reaction
Use Solubility Rules and Determine the States
of the Products
AgNO3(aq) + KCl(aq) → AgCl(?) + KNO3 (?)
Zn(NO3)2(aq) + BaCr2O7(aq) →ZnCr2O7 (?)+Ba(NO3)2 (?)
CdCl2(aq) + Na2S(aq) → CdS(?) + 2NaCl(?)
What Really Happens in
Solution?
Look at each substance on an individual
basis
Determine if it’s a strong electrolyte or
weak electrolyte
Electrolytes and Nonelectrolytes
Electrolyte: substance that dissolved in
water produces a solution that conducts
electricity
Contains ions
Nonelectrolyte: substance that dissolved in
water produces a solution that does not
conduct electricity
Does not contain ions
Copyright McGraw-Hill 2009
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Dissociation - ionic compounds
separate into constituent ions when
dissolved in solution
Ionization - formation of ions by
molecular compounds when dissolved
Copyright McGraw-Hill 2009
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Strong and weak electrolytes
Strong Electrolyte: 100% dissociation
All water soluble ionic compounds,
strong acids and strong bases
Weak electrolytes
Exist
mostly as the molecular form in
solution
Do not dissociate when dissolved in
water
Insoluble ionic compounds, Weak acids
and weak bases
Copyright McGraw-Hill 2009
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Strong Electrolytes
When dissolved in water, dissociate or ionize
Soluble Ionic Compounds
EX) NaNO3, MgCl2, Ca(C2H3O2)2
Strong Acids
EX) HCl, HBr, HI
Oxyacids with #O’s>#H’s by 2/more
Strong Bases
EX) All Hydroxides except those that are insoluble
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Weak Electrolytes
Do not dissociate or ionize when
dissolved in water
Insoluble ionic compounds
Weak Acids (must know these, memorize)
AgCl, Ca(OH)2
HF, HCN, HC2H3O2
Oxyacids #O’s>#H’s by 1/less
Weak Bases (must know these, memorize)
NH3
For Every Double Displacement Reaction
Three Types of Equations
Molecular Equation- written as whole formulas, not the ions.
K2CrO4(aq) + Ba(NO3)2(aq) →
Complete Ionic equation show dissolved electrolytes as the
ions and any precipitates formed.
2K+(aq)+CrO4-2(aq)+Ba+2(aq)+2NO3-(aq)→BaCrO4 (s)+2K+(aq)+2NO3- (aq)
Spectator ions are those that don’t react.
For Every Double Displacement Reaction
Three Types of Equations
Net Ionic equations show only those ions that
react, not the spectator ions…they cancel out to
make the net ionic equation
+2
-2
Ba
(aq) + CrO4
(aq) → BaCrO4(s)
Write the molecular equation, the complete ionic
equation and the net ionic equation for the
reactions when these solutions are mixed.
Example:
iron (III) sulfate and potassium sulfide
lead (II) nitrate and sulfuric acid.
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For Every Double Displacement Reaction
Three Types of Equations
Write the molecular equation, the
complete ionic equation and the net ionic
equation for the reactions when these
solutions are mixed.
Example:
iron (III) sulfate and potassium sulfide
lead (II) nitrate and sulfuric acid.
Ch 4 Chemical Reactions
Big Idea 3: Changes in matter involve the
rearrangement and/or reorganization of atoms
and/or the transfer of electrons
Ch 4 Chemical Reactions
Enduring understanding 3.B:
Chemical reactions can be classified by considering
what the reactants are, what the products are, or
how they change from one into the other. Classes
of chemical reactions include synthesis,
decomposition, acid-base, and oxidation-reduction
reactions.
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Chapter 4
Types of Chemical Reactions
Writing Chemical Reactions
Ch 4 Chemical Reactions
Sec 4.5 Some Common Oxidation Reduction
Reactions
Identify the type of chemical reaction based on its
characteristics
Use the activity series of metals to predict the
products of a single displacement reaction
Predict products of a combination, combustion,
displacement, or decomposition reaction based
upon the reactants
Types of Reactions
Many chemical
reactions have
defining
characteristics
which allow
them to be
classified as to
type.
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Types of Chemical Reactions
The five types of chemical reactions in this
unit are:
Combination/Synthesis
Decomposition
Single Replacement
Combustion
Double Replacement
Combination Reactions
aka Synthesis Reactions
Two or more substances combine to form
one substance.
The general form is A + X AX
Example:
Magnesium + chlorine magnesium
chloride
Mg + Cl2 MgCl2
Combination Reactions
aka Synthesis Reactions
Combination reactions may also be called
composition or synthesis reactions.
Some types of combination reactions:
Combination of elements
K
+ Cl2 One product will be formed
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Combination Reactions
aka Synthesis Reactions
K + Cl2 Write the ions: K+ Cl-
Balance the charges: KCl
Balance the equation: 2K + Cl2 2KCl
Combination Reactions
aka Synthesis Reactions
Some types of combination reactions:
Oxide + water Add algebraically and check valence charges
Nonmetal
oxide + water acid
+ H2O H2SO3
Metal oxide + water base
BaO + H2O Ba(OH)2
SO2
Combination Reactions
aka Synthesis Reactions
Some types of combination reactions:
Metal oxides + nonmetal
oxides→
add algebraically (check valence charges)
Na2O
+ CO2 Na2CO3
CaO + SO2 CaSO3
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Decomposition Reactions
One substance (Binary Compound)
reacts to form two or more substances.
The general form is AX A + X
When forming an element as a product, check if
diatomic
Example:
Water can be decomposed by
electrolysis.
2H2O 2H2 + O2
Decomposition Reactions
Types of Decomposition Reactions:
heated, some carbonates
break down to form a metal oxide
and carbon dioxide.
CaCO3 CaO + CO2
H2CO3 H2O + CO2
When
Decomposition Reactions
Types of decomposition reactions:
Some metal hydroxides decompose
into metal oxides and water when
heated.
Ca(OH)2 CaO + H2O
Note that this is the reverse of a similar
combination reaction.
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Decomposition Reactions
Types of decomposition reactions:
Metal chlorates decompose into
metal chlorides and oxygen when
heated.
2KClO3 2KCl + 3O2
Zn(ClO3)2 ZnCl2 + 3O2
Some of these reactions are used in
explosives.
Decomposition Reactions
Some substances can easily
decompose:
Ammonium hydroxide is actually
ammonia gas dissolved in water. (add
algebraically)
NH4OH NH3 + H2O
Ternary acids decompose into water
and an oxide. (add algebraically)
H2CO3 H2O + CO2
Decomposition Reactions
Some decomposition reactions are
difficult to predict.
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Single Replacement Reactions
A metal element will replace a metal
ion in a binary compound.
The general form is A + BX AX + B
First, check the Activity Series
Is element A stronger than element B?
Single Replacement Reactions
First, check the Activity Series
Is element A stronger than element B?
Single Replacement Reactions
A nonmetal will replace a nonmetal ion
in a binary compound.
The general form is Y + BX BY + X
Use the Activity Series for Nonmetals…The
Halogen Family on the Periodic Table
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Single Replacement Reactions
Examples:
Ni + AgNO3 Nickel replaces the metallic ion Ag+.
The silver becomes free silver and the
nickel becomes the nickel(II) ion.
Ni + AgNO3 Ag + Ni(NO3)2
Balance the equation:
Ni + 2AgNO3 2Ag + Ni(NO3)2
Single Replacement Reactions
Not all single replacement reactions that
can be written actually happen.
The metal must be more active than the
metal ion.
Aluminum is more active than iron in
Al + Fe2O3→
Thermite Reaction
http://www.youtube.com/watch?v=M3Zko
NF2ybg
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Thermite Reaction
Example of a Single replacement Reaction
Al + Fe2O3 Aluminum will replace iron(III) as
was seen in the video.
Iron(III) becomes Fe and aluminum
metal becomes Al3+.
2Al + Fe2O3 2Fe + Al2O3
Single Replacement Reactions
An active nonmetal can replace a less
active nonmetal.
The halogen (F2, Cl2, Br2, I2)
reactions are good examples.
F2 is the most active and I2 is the
least.
Cl2 +2 NaI 2 NaCl + I2
Combustion Reaction
When an element is burned, it
combines with oxygen, a combustion
reaction results.
The combustion reaction may look
similar to a combination reaction, but
the difference here is oxygen is
ALWAYS A REACTANT
2Mg + O2 2MgO.
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Combustion Reaction
Methane, CH4, is natural gas. It is a
“hydrocarbon”
When hydrocarbon compounds
are burned in oxygen, the products
are water and carbon dioxide.
CH4 + O2 CO2 + H2O
CH4 + 2O2 CO2 + 2H2O
Combustion Reactions
Combustion reactions involve light
and heat energy released.
Natural gas, propane, gasoline, etc.
are burned to produce heat energy.
Most of these organic reactions
(hydrocarbon compounds)
produce water and carbon dioxide.
Classify each of the following as to type:
H2 + Cl2 2HCl
Ca + 2H2O Ca(OH)2 + H2
Single replacement
2CO + O2 2CO2
Combination
Combination and combustion
2KClO3 2KCl + 3O2
Decomposition
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Double Displacement
Reactions
2 Ionic Compounds
Each has a cation (+ ion) and
an anion (- ion)
Cations(+ ion) and Anions(- ion)
Exchange partners
Must always form a pure substance in
the form of a solid, liquid or gas
(s), (l), (g) [(s) known as a precipitate]
Double Displacement
Reactions
2 “special types”
Acid base reaction
(aka Neutralization Reaction)
Precipitation reaction
Ch 4 Chemical Reactions
Big Idea 3: Changes in matter involve the
rearrangement and/or reorganization of atoms
and/or the transfer of electrons
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Ch 4 Chemical Reactions
Enduring understanding 3.B:
Chemical reactions can be classified by considering
what the reactants are, what the products are, or
how they change from one into the other. Classes of
chemical reactions include synthesis, decomposition,
acid-base, and oxidation-reduction reactions.
Essential knowledge 3.B.2:
In a neutralization reaction, protons are
transferred from an acid to a base.
Acid Base Reactions
special double replacement reaction
Acid-Base
For our purposes an acid is a proton
donor.
a base is a proton acceptor usually OHWhat is the net ionic equation for the
reaction of HCl(aq) and KOH(aq)?
Acid + Base → salt + water
H+ + OH- → H2O
Acid - Base Reactions
special double replacement reaction
Often called a neutralization reaction Because
the acid neutralizes the base.
Often titrate to determine concentrations.
Solution of known concentration (titrant),
is added to the unknown (analyte),
until the equivalence point is reached where
enough titrant has been added to neutralize it.
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Acid-Base Reaction
special double replacement reaction
HCl is mixed with Ba(OH)2 . What is the
neutralization reaction?
Why is it called a neutralization reaction?
Ch 4 Oxidation Reduction
Reactions
Ch 4 Chemical Reactions
Big Idea 3: Changes in matter involve the
rearrangement and/or reorganization of atoms
and/or the transfer of electrons
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Ch 4 Chemical Reactions
Enduring understanding 3.B:
Chemical reactions can be classified by considering
what the reactants are, what the products are, or
how they change from one into the other. Classes of
chemical reactions include synthesis, decomposition,
acid-base, and oxidation-reduction reactions.
Essential knowledge 3.B.3: In oxidation-reduction
(redox) reactions, there is a net transfer of electrons.
The species that loses electrons is oxidized, and the
species that gains electrons is reduced.
Sec 4.5 Oxidation Reduction
Reactions Objectives
Define oxidation–reduction reaction.
Learn the oxidation-number rules.
Assign oxidation numbers
Write the half-reactions of an oxidation–
reduction reaction.
Determine the species undergoing
oxidation and reduction.
Types of Chemical Reactions
Oxidation-Reduction called Redox
Substances are formed through the
transfer of electrons.
An Oxidation-reduction reaction involves
the transfer of electrons.
We need a way of keeping track.
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Types of Chemical Reactions
The four types of chemical reactions in
this unit can be classified as redox are:
Combination/Synthesis
Decomposition
Single Replacement
Combustion
Double Replacement
Oxidation States
A way of keeping track of the electrons.
Not necessarily true of what is in nature,
but it works.
need the rules for assigning (memorize).
Oxidation states
• The oxidation state of elements in their
standard states is zero.
• Oxidation state for monoatomic ions are the
same as their charge.
• Oxygen is assigned an oxidation state of -2 in its
covalent compounds except as a peroxide.
• In compounds with nonmetals hydrogen is
assigned the oxidation state +1.
• In its compounds fluorine is always –1.
• The sum of the oxidation states must be zero in
compounds or equal the charge of the ion.
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Oxidation States
Assign the oxidation states to each
element in the following.
CO2
NO3H2SO4
Fe2O3
Fe3O4
Oxidation-Reduction Reactions
Transfer electrons, so the oxidation
states change.
Na + 2Cl2 → 2NaCl
CH4 + 2O2 → CO2 + 2H2O
Oxidation is the loss of electrons.
Reduction is the gain of electrons.
OIL RIG
LEO GER
Oxidation-Reduction Reactions
Oxidation means an increase in oxidation
state - lose electrons.
Reduction means a decrease in oxidation
state - gain electrons.
The substance that is oxidized is called the
reducing agent.
The substance that is reduced is called the
oxidizing agent.
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Agents
Oxidizing agent gets reduced.
Gains electrons.
More negative oxidation state.
Reducing agent gets oxidized.
Loses electrons.
More positive oxidation state.
EXAMPLE PROBLEM
Directions: Identify the Oxidizing agent,
Reducing agent, Substance oxidized,
Substance reduced
Fe (s) + O2(g) → Fe2O3(s)
Fe2O3(s)+ 3 CO(g) → 2 Fe(l) + 3 CO2(g)
SO32- + H+ + MnO4- → SO42- + H2O + Mn2+
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