Download chemical reaction and quantities

Chapter 5 Chemical Reactions
and Quantities
Type of Reactions
5.3
Types of Reactions
Chemical reactions can be classified as
§  Combination reactions.
§  Decomposition reactions.
§  Single Replacement reactions.
§  Double Replacement reactions.
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Combination
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Formation of MgO
In a combination reaction,
§  Two or more elements (or simple compounds)
combine to form one product
A
+
B
A
B
2Mg(s) + O2(g)
2MgO(s)
2Na(s) + Cl2(g)
2NaCl(s)
SO3(g) + H2O(l)
H2SO4(aq)
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Decomposition
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Decomposition of HgO
In a decomposition reaction,
§  One substance splits into two or more simpler
substances.
2HgO(s)
2Hg(l) + O2(g)
2KClO3(s)
2KCl(s) + 3O2(g)
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Learning Check
Single Replacement
In a single replacement reaction,
§  One element takes the place of a different element in
a reacting compound.
Classify the following reactions as
1) combination or 2) decomposition:
___A. H2(g) + Br2(g)
2HBr(l)
___B. Al2(CO3)3(s)
Al2O3(s) + 3CO2(g)
___C. 4Al(s) + 3C(s)
Al4C3(s)
Zn(s) + 2HCl(aq)
ZnCl2(aq) + H2(g)
Fe(s) + CuSO4(aq)
FeSO4(aq) + Cu(s)
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Zn and HCl is a Single Replacement
Reaction
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Double Replacement
In a double replacement,
§  Two elements in the reactants exchange places.
AgNO3(aq) + NaCl(aq)
AgCl(s) + NaNO3(aq)
ZnS(s)
ZnCl2(aq) + H2S(g)
+ 2HCl(aq)
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Example of a Double Replacement
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Learning Check
Classify the following reactions as
1) single replacement 2) double replacement
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A. 2Al(s) + 3H2SO4(aq)
Al2(SO4)3(s) + 3H2(g)
B. Na2SO4(aq) + 2AgNO3(aq)
Ag2SO4(s) + 2NaNO3(aq)
C. 3C(s) + Fe2O3(s)
2Fe(s) + 3CO(g)
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Chapter 5 Chemical Reactions
and Quantities
Learning Check
Identify each reaction as
1) combination
3) single replacement
A.
B.
C.
D.
E.
3Ba(s) + N2(g)
2Ag(s) + H2S(aq)
SiO2(s) + 4HF(aq)
PbCl2(aq) + K2SO4(aq)
K2CO3(s)
5.4
Oxidation-Reduction Reactions
2) decomposition
4) double replacement
Ba3N2(s)
Ag2S(s) + H2(g)
SiF4(s) + 2H2O(l)
2KCl(aq) + PbSO4(s)
K2O(aq) + CO2(g)
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Oxidation and Reduction
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Electron Loss and Gain
An oxidation-reduction reaction
An oxidation-reduction reaction
§  Provides us with energy from food.
§  Provides electrical energy in batteries.
§  Occurs when iron rusts.
4Fe(s) + 3O2(g)
2Fe2O3(s)
§  Transfers electrons from one reactant to another.
A Loss of Electrons is Oxidation
Zn(s)
Zn2+(aq) + 2e-
(LEO)
A Gain of Electrons is Reduction
Cu2+(aq) + 2eCu(s)
(GER)
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Zn and Cu2+
Oxidation and Reduction
oxidation
Zn(s)
Silvery metal
Zn2+(aq) + 2ereduction
Cu2+(aq) + 2eBlue
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Cu(s)
orange
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Electron Transfer from Zn to Cu2+
Learning Check
Identify each of the following as
1) oxidation or 2) reduction:
Oxidation: electron loss
__A.
Sn(s)
Sn4+(aq) + 4e−
__B.
Fe3+(aq) + 1e−
Fe2+(aq)
__C.
Cl2(g) + 2e−
2Cl-(aq)
Reduction: electron gain
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Writing Oxidation and Reduction
Reactions
Learning Check
Write the separate oxidation and reduction reactions
for the following equation.
2Cs(s) + F2(g)
In light-sensitive sunglasses, UV light initiates
an oxidation-reduction reaction.
uv light
Ag+ + Cl−
Ag + Cl
2CsF(s)
Each cesium atom loses an electron to form cesium
ion.
2Cs(s)
2Cs+(s) + 2e−
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A. Which reactant is oxidized?
oxidation
B. Which reactant is reduced?
Fluorine atoms gain electrons to form fluoride ions.
F2(s) + 2e-
2F−(s)
reduction
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Learning Check
Identify the substances that are oxidized and reduced in
each of the following reactions:
A. Mg(s) + 2H+(aq)
Mg2+(aq) + H2(g)
B. 2Al(s) + 3Br2(g)
2AlBr3(s)
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TYPES OF CHEMICAL REACTIONS
•  Chemical reactions are often classified into categories
according to characteristics of the reactions. The
following is a useful classification scheme:
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Chapter 5 Chemical Reactions
and Quantities
Collection Terms
A collection term states a specific number of items.
5.5
The Mole
§  1 dozen donuts
= 12 donuts
§  1 ream of paper = 500 sheets
§  1 case = 24 cans
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A Mole of Atoms
A Mole of a Compound
A mole
A mole is a collection that contains
§  Of a covalent compound has Avogadro s number of
§  The same number of particles as there are carbon
atoms in 12.0 g of carbon
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molecules.
12C.
§  6.02 x 1023 atoms of an element (Avogadro s number).
1 mole element
Number of Atoms
1 mole C
= 6.02 x 1023 C atoms
1 mole Na
= 6.02 x
1023
1 mole Au
= 6.02 x 1023 Au atoms
1 mole CO2 = 6.02 x 1023 CO2 molecules
1 mole H2O = 6.02 x 1023 H2O molecules
§  Of an ionic compound contains Avogadro s number of
formula units.
Na atoms
1 mole NaCl
= 6.02 x 1023 NaCl formula units
1 mole K2SO4 = 6.02 x 1023 K2SO4 formula units
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Particle in One-Mole Samples
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Avogadro s Number
Avogadro s number 6.02 x 1023 can be written as an
TABLE 5.3
equality and two conversion factors.
Equality:
1 mole
= 6.02 x 1023 particles
Conversion Factors:
6.02 x 1023 particles
1 mole
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and
1 mole
6.02 x 1023 particles
30
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Using Avogadro s Number
Using Avogadro s Number
Avogadro s number is used to convert
moles of a substance to particles.
Avogadro s number is used to convert
particles of a substance to moles.
How many Cu atoms are in
How many moles of CO2 are in
2.50 x 1024 molecules CO2?
0.50 mole Cu?
2.50 x 1024 molecules CO2 x
0.50 mole Cu x 6.02 x 1023 Cu atoms
1 mole Cu
= 3.0 x 1023 Cu atoms
1 mole CO2
6.02 x 1023 molecules CO2
= 4.15 moles CO2
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Learning Check
Subscripts and Moles
1. The number of atoms in 2.0 moles Al is
The subscripts in a formula give
§  The relationship of atoms in the formula.
§  The moles of each element in 1 mole of compound.
A. 2.0 Al atoms
B. 3.0 x 1023 Al atoms
C. 1.2 x 1024 Al atoms
Glucose
C6H12O6
2. The number of moles of S in 1.8 x 1024 atoms S is
A. 1.0 mole S atoms
In 1 molecule: 6 atoms C 12 atoms H 6 atoms O
In 1 mole:
6 moles C 12 moles H 6 moles O
B. 3.0 moles S atoms
C. 1.1 x 1048 moles S atoms
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Subscripts State Atoms and Moles
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Factors from Subscripts
Subscripts used for conversion factors
§  Relate moles of each element in 1 mole compound.
§  For aspirin C9H8O4 can be written as:
9 moles C
1 mole C9H8O4
8 moles H
1 mole C9H8O4
4 moles O
1 mole C9H8O4
1 mole C9H8O4
8 moles H
1 mole C9H8O4
4 moles O
and
1 mole C9H8O4
9 moles C
1 mole C9H8O4
=
9 moles C 8 moles H
4 moles O
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Learning Check
5.6 Molar Mass
A. How many moles O are in 0.150 mole aspirin C9H8O4?
The molar mass is
§  The mass of one mole of a substance.
§  The atomic mass of an element expressed in grams.
B. How many O atoms are in 0.150 mole aspirin C9H8O4?
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Learning Check
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Molar Mass of CaCl2
Give the molar mass to the nearest 0.1 g.
A. K
=
________
B. Sn
=
________
§  For a compound, the molar mass is the sum of the molar
masses of the elements in the formula. We calculate the molar
mass of CaCl2 to the nearest 0.1 g as follows.
Element
Number of
Moles
Atomic Mass
Total Mass
Ca
1
40.1 g/mole
40.1 g
Cl
2
35.5 g/mole
71.0 g
CaCl2
111.1 g
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Molar Mass of K3PO4
Learning Check
Calculate the molar mass to the nearest 0.1g
Determine the molar mass of K3PO4 to 0.1 g.
A. K2O =
Element
Number of
Moles
Atomic Mass
K
3
39.1 g/mole
117.3 g
P
1
31.0 g/mole
31.0 g
O
4
16.0 g/mole
K3PO4
40
______ g
Total Mass in
K3PO4
B. Al(OH)3 = ______ g
64.0 g
212.3 g
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Conversion Factors from Molar
Mass
Learning Check
Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of
serotonin by the brain. What is the molar mass of Prozac?
1) 40.0 g/mole
Methane CH4 known as natural gas is used in gas cook
tops and gas heaters.
1 mole CH4 =
2) 262 g/mole
16.0 g
The molar mass of methane can be written as conversion
factors.
16.0 g CH4
and
1 mole CH4
1 mole CH4
16.0 g CH4
3) 309 g/mole
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Learning Check
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Calculations Using Molar Mass
Acetic acid C2H4O2 gives the sour taste to vinegar. Write two
molar mass conversion factors for acetic acid.
§  Mole factors are used to convert between the grams of a substance
and the number of moles.
Grams
Mole factor
Moles
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Calculating Grams from Moles
Learning Check
Aluminum is often used for the structure of
lightweight bicycle frames. How many grams
of Al are in 3.00 moles of Al?
3.00 moles Al x
27.0 g Al
1 mole Al
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The artificial sweetener aspartame (Nutri-Sweet) C14H18N2O5
is used to sweeten diet foods, coffee and soft drinks. How
many moles of aspartame are present in 225 g of
aspartame?
= 81.0 g Al
mole factor for Al
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