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Type of Reactions
Chemical reactions are classified into
several general types
 Combination (Synthesis)
 Decomposition
 Single Replacement
 Double Replacement (Metathesis)
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Combination (Synthesis)
Two or more elements or simple
compounds combine to form
(synthesize) one product
A + B
AB
2Mg + O2
2MgO
2Na + Cl2
2NaCl
SO3 + H2O
H2SO4
2
Decomposition
One substance is broken down (split)
into two or more simpler substances.
AB
A + B
2HgO
2Hg + O2
2KClO3
2KCl + 3 O2
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Learning Check R1
Classify the following reactions as
1) combination or 2) decomposition:
___A. H2 + Br2
2HBr
___B. Al2(CO3)3
Al2O3 + 3CO2
___C. 4 Al + 3C
Al4C3
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Solution R1
Classify the following reactions as
1) combination or 2) decomposition:
_1_A. H2 + Br2
2HBr
_2_B. Al2(CO3)3
Al2O3 + 3CO2
_1_C. 4 Al + 3C
Al4C3
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Single Replacement
One element takes the place of an
element in a reacting compound.
A + BC
AB + C
Zn + 2HCl
ZnCl2 + H2
Fe + CuSO4
FeSO4 + Cu
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Double Replacement
Two elements in reactants take the place
of each other
AB + CD
AD + CB
AgNO3 + NaCl
AgCl + NaNO3
ZnS
ZnCl2 + H2S
+ 2HCl
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Learning Check R2
Classify the following reactions as
1) single replacement
2) double replacement
__A. 2Al + 3H2SO4
Al2(SO4)3 + 3H2
__B. Na2SO4 + 2AgNO3
Ag2SO4 + 2NaNO3
__C. 3C + Fe2O3
2Fe + 3CO
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Solution R2
Classify the following reactions as
1) single replacement
2) double replacement
1_A. 2Al + 3H2SO4
Al2(SO4)3 + 3H2
2_B. Na2SO4 + 2AgNO3
Ag2SO4 + 2NaNO3
1_C. 3C + Fe2O3
2Fe + 3CO
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Combustion
A reaction in which a compound (often
carbon) reacts with oxygen
C + O2
CO2
CH4 + 2O2
CO2 + 2H2O
C3H8 + 5O2
3CO2 + 4H2O
C6H12O6 + 6O2
6CO2 + 6H2O
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Learning Check R3
Balance the combustion equation
___C5H12 + ___O2
___CO2 + ___H2O
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Solution R3
Balance the combustion equation
1 C5H12 + 8 O2
5 CO2 + 6 H2O
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Oxidation and Reduction
Reactions that involve a loss or gain of
electrons
Occurs in many of the types of reactions
and combustion
Important in food metabolism, batteries,
rusting of metals
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Requirements for OxidizationReduction
Electrons are transferred
Two processes occur
Oxidation = Loss of electrons (LEO)
Zn
Zn2+ + 2e-
Reduction = Gain of electrons (GER)
Cu2+ + 2e-
Cu
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Balanced Red-Ox Equations
Combine the oxidation and reduction
reactions to make
Loss of electrons = Gain of electrons
Zn + Cu2+ + 2e-
Zn2+ + 2e- + Cu
Zn + Cu2+
Zn2+ + Cu
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Learning Check R3
Identify the following as an 1) oxidation or
a reduction process:
__A.
Sn
Sn4+ + 4e-
__B.
Fe3+ + 1e-
Fe2+
__C.
Cl2 + 2e-
2Cl-
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Solution R3
Identify the following as an 1) oxidation or
a reduction process:
1_ A.
Sn
Sn4+ + 4e-
2_ B.
Fe3+ + 1e-
Fe2+
2_ C.
Cl2 + 2e-
2Cl-
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Redox
• REDOX stands for REDuction/OXidation
• Oxidation refers to a loss of electrons
• Reduction refers to a gain of electrons
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•
•
•
•
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LEO –GER
Loss Electrons = Oxidation
Gain Electrons = Reduction
OIL-RIG
Oxidation Is Loss
Reduction Is Gain
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oxidation = loss of e–
X X+ + e–
reduction = gain of e–
X + e– X–
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Oxidation numbers
• We will see that there is a simple way to keep
track of oxidation and reduction
• This is done via “oxidation numbers”
• An oxidation number is the charge an atom
would have if electrons in its bonds belonged
completely to the more electronegative atom
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Rules
1. Any element, when not combined with atoms
of a different element, has an oxidation # of
zero. (O in O2 is zero)
2. Any simple monatomic ion (one-atom ion) has
an oxidation number equal to its charge (Na+
is +1, O2– is –2)
3. The sum of the oxidation numbers of all of the
atoms in a formula must equal the charge
written for the formula. (if the oxidation
number of O is –2, then in CO32– the oxidation
number of C is +4)
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Rules
4. In compounds, the oxidation # of IA metals is
+1, IIA is +2, and aluminum (in IIIA) is +3
5. In ionic compounds, the oxidation # of a
nonmetal or polyatomic ion is equal to the
charge of its associated ion. (CuCl2, Cl is –1)
6. F is always –1, O is always –2 (unless
combined with F), H is usually +1
total +1 +5 -6 +2 +12 -14 -4 +6 -2 +1 -1 +2 +5 -8
Ox.# +1 +5 -2 +1 +6 -2 -2 +1 -2 +1 -1 +1 +5 -2
HNO 3 K2Cr2O7 C2H6O AgI H2PO4–
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11.1
Writing Chemical Equations
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11.2
Classifying Reactions
– Combination Reactions
• A combination reaction is a chemical change in
which two or more substances react to form a
single new substance.
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11.2
Classifying Reactions
– Decomposition Reactions
• A decomposition reaction is a chemical change
in which a single compound breaks down into
two or more simpler products.
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11.2
Classifying Reactions
– Single-Replacement Reactions
• A single-replacement reaction is a chemical
change in which one element replaces a
second element in a compound.
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11.2
Classifying Reactions
• The activity series of
metals lists metals in
order of decreasing
reactivity.
• Generally, the higher
in the periodic table,
the more reactive.
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11.2
Classifying Reactions
– Double-Replacement Reactions
• A double-replacement reaction is a chemical
change involving an exchange of positive ions
between two compounds.
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11.3
Predicting the Formation of a
Precipitate
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11.2
Classifying Reactions
– Combustion Reactions
• A combustion reaction is a chemical change in
which an element or a compound reacts with
oxygen, often producing energy in the form of
heat and light.
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11.3
Net Ionic Equations
• A complete ionic equation is an equation that
shows dissolved ionic compounds as
dissociated free ions.
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11.3
Net Ionic Equations
• An ion that appears on both sides of an
equation and is not directly involved in the
reaction is called a spectator ion.
• The net ionic equation is an equation for a
reaction in solution that shows only those
particles that are directly involved in the
chemical change.
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11.3
Net Ionic Equations
– A net ionic equation shows only those
particles involved in the reaction and is
balanced with respect to both mass and
charge.
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11.3
Net Ionic Equations
• Sodium ions and nitrate ions are not changed
during the chemical reaction of silver nitrate
and sodium chloride so the net ionic equation is
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11.3
• Will a precipitate form when a sodium
carbonate solution is mixed with a barium
nitrate solution?
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11.3
Predicting the Formation of a
Precipitate
• Sodium nitrate is soluble but barium carbonate
is insoluble. The net ionic equation is
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