Type of Reactions Chemical reactions are classified into several general types Combination...
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Transcript of Type of Reactions Chemical reactions are classified into several general types Combination...
Type of Reactions
Chemical reactions are classified into several general types
Combination (Synthesis)
Decomposition
Single Replacement
Double Replacement (Metathesis)
1
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
4
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
5
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 + 2HCl ZnCl2 + H2S
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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 + 3CO8
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 + 3CO9
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 Oxidization-Reduction
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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RedoxRedox• REDOX stands for REDuction/OXidation• Oxidation refers to a loss of electrons• Reduction refers to a gain of electrons
• 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 numbersOxidation 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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RulesRules 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 CO3
2– the oxidation number of C is +4)
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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
totalOx.#
Rules Rules
+1+1
-2-6+5
+5 +1+2
-2-14+12
+6 +1+6
-2-2-4
-2 -1-1+1
+1H N O 3 C2H6OK2Cr2O7 AgI
+1+2
-2-8+5
+5H2PO4
–
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Writing Chemical Equations
11.1
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Classifying Reactions
– Combination Reactions• A combination reaction is a chemical change in
which two or more substances react to form a single new substance.
11.2
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Classifying Reactions
– Decomposition Reactions• A decomposition reaction is a chemical change
in which a single compound breaks down into two or more simpler products.
11.2
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Classifying Reactions
– Single-Replacement Reactions• A single-replacement reaction is a chemical
change in which one element replaces a second element in a compound.
11.2
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Classifying Reactions• The activity series of
metals lists metals in order of decreasing reactivity.
• Generally, the higher in the periodic table, the more reactive.
11.2
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Classifying Reactions
– Double-Replacement Reactions• A double-replacement reaction is a chemical
change involving an exchange of positive ions between two compounds.
11.2
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Predicting the Formation of a Precipitate
11.3
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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.
11.2
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Net Ionic Equations
• A complete ionic equation is an equation that shows dissolved ionic compounds as dissociated free ions.
11.3
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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.
11.3
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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.
11.3
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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
11.3
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40
41
42
• Will a precipitate form when a sodium carbonate solution is mixed with a barium nitrate solution?
11.3
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Predicting the Formation of a Precipitate
• Sodium nitrate is soluble but barium carbonate is insoluble. The net ionic equation is
11.3
44