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Chapter 5 Chemical Reactions and Quantities 5.3
Types of Reactions
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Type of Reactions
Chemical reactions can be classified as § Combination reactions. § Decomposition reactions.
§ Single Replacement reactions.
§ Double Replacement reactions.
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Combination
In a combination reaction, § Two or more elements (or simple compounds)
combine to form one product
+
2Mg(s) + O2(g) 2MgO(s) 2Na(s) + Cl2(g) 2NaCl(s)
SO3(g) + H2O(l) H2SO4(aq)
A B A B
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Formation of MgO
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Decomposition
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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Decomposition of HgO
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Learning Check
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)
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Single Replacement
In a single replacement reaction, § One element takes the place of a different element in
a reacting compound.
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) + 2HCl(aq) ZnCl2(aq) + H2S(g)
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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
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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Learning Check
Identify each reaction as 1) combination 2) decomposition 3) single replacement 4) double replacement
A. 3Ba(s) + N2(g) Ba3N2(s) B. 2Ag(s) + H2S(aq) Ag2S(s) + H2(g) C. SiO2(s) + 4HF(aq) SiF4(s) + 2H2O(l) D. PbCl2(aq) + K2SO4(aq) 2KCl(aq) + PbSO4(s) E. K2CO3(s) K2O(aq) + CO2(g)
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Chapter 5 Chemical Reactions and Quantities
5.4 Oxidation-Reduction Reactions
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Oxidation and Reduction
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)
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An oxidation-reduction reaction § Transfers electrons from one reactant to another.
A Loss of Electrons is Oxidation (LEO) Zn(s) Zn2+(aq) + 2e-
A Gain of Electrons is Reduction (GER) Cu2+(aq) + 2e- Cu(s)
Electron Loss and Gain
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Oxidation and Reduction
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Zn and Cu2+
oxidation Zn(s) Zn2+(aq) + 2e- Silvery metal
reduction Cu2+(aq) + 2e- Cu(s)
Blue orange
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Electron Transfer from Zn to Cu2+
Oxidation: electron loss
Reduction: electron gain
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Identify each of the following as 1) oxidation or 2) reduction:
__A. Sn(s) Sn4+(aq) + 4e−
__B. Fe3+(aq) + 1e− Fe2+(aq)
__C. Cl2(g) + 2e− 2Cl-(aq)
Learning Check
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Write the separate oxidation and reduction reactions for the following equation. 2Cs(s) + F2(g) 2CsF(s)
Each cesium atom loses an electron to form cesium ion. 2Cs(s) 2Cs+(s) + 2e− oxidation
Fluorine atoms gain electrons to form fluoride ions. F2(s) + 2e- 2F−(s) reduction
Writing Oxidation and Reduction Reactions
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In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction. uv light
Ag+ + Cl− Ag + Cl A. Which reactant is oxidized? B. Which reactant is reduced?
Learning Check
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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)
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 5.5
The Mole
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Collection Terms
A collection term states a specific number of items. § 1 dozen donuts = 12 donuts
§ 1 ream of paper = 500 sheets
§ 1 case = 24 cans
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A mole is a collection that contains § The same number of particles as there are carbon
atoms in 12.0 g of carbon 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 Na atoms 1 mole Au = 6.02 x 1023 Au atoms
A Mole of Atoms
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A mole § Of a covalent compound has Avogadro’s number of
molecules. 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. 1 mole NaCl = 6.02 x 1023 NaCl formula units 1 mole K2SO4 = 6.02 x 1023 K2SO4 formula units
A Mole of a Compound
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Particle in One-Mole Samples
TABLE 5.3
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Avogadro’s number 6.02 x 1023 can be written as an equality and two conversion factors.
Equality: 1 mole = 6.02 x 1023 particles
Conversion Factors: 6.02 x 1023 particles and 1 mole 1 mole 6.02 x 1023 particles
Avogadro’s Number
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Using Avogadro’s Number
Avogadro’s number is used to convert moles of a substance to particles. How many Cu atoms are in 0.50 mole Cu? 0.50 mole Cu x 6.02 x 1023 Cu atoms
1 mole Cu = 3.0 x 1023 Cu atoms
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Using Avogadro’s Number
Avogadro’s number is used to convert particles of a substance to moles. How many moles of CO2 are in 2.50 x 1024 molecules CO2? 2.50 x 1024 molecules CO2 x 1 mole CO2
6.02 x 1023 molecules CO2
= 4.15 moles CO2
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1. The number of atoms in 2.0 moles Al is A. 2.0 Al atoms
B. 3.0 x 1023 Al atoms C. 1.2 x 1024 Al atoms
2. The number of moles of S in 1.8 x 1024 atoms S is A. 1.0 mole S atoms B. 3.0 moles S atoms C. 1.1 x 1048 moles S atoms
Learning Check
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Subscripts and Moles
The subscripts in a formula give § The relationship of atoms in the formula. § The moles of each element in 1 mole of compound.
Glucose C6H12O6
In 1 molecule: 6 atoms C 12 atoms H 6 atoms O In 1 mole: 6 moles C 12 moles H 6 moles O
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Subscripts State Atoms and Moles
1 mole C9H8O4 = 9 moles C 8 moles H 4 moles O
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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 8 moles H 4 moles O 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 and 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 9 moles C 8 moles H 4 moles O
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Learning Check
A. How many moles O are in 0.150 mole aspirin C9H8O4? B. How many O atoms are in 0.150 mole aspirin C9H8O4?
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The molar mass is § The mass of one mole of a substance. § The atomic mass of an element expressed in grams.
5.6 Molar Mass
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Give the molar mass to the nearest 0.1 g. A. K = ________
B. Sn = ________
Learning Check
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Molar Mass of CaCl2
§ 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
Determine the molar mass of K3PO4 to 0.1 g.
Element Number of Moles
Atomic Mass Total Mass in K3PO4
K 3 39.1 g/mole 117.3 g
P 1 31.0 g/mole 31.0 g
O 4 16.0 g/mole 64.0 g
K3PO4 212.3 g
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Calculate the molar mass to the nearest 0.1g A. K2O = ______ g
B. Al(OH)3 = ______ g
Learning Check
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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 2) 262 g/mole 3) 309 g/mole
Learning Check
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Methane CH4 known as natural gas is used in gas cook tops and gas heaters.
1 mole CH4 = 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
Conversion Factors from Molar Mass
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Acetic acid C2H4O2 gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid.
Learning Check
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§ Mole factors are used to convert between the grams of a substance
and the number of moles.
Calculations Using Molar Mass
Grams
Mole factor Moles
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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 = 81.0 g Al
1 mole Al mole factor for Al
Calculating Grams from Moles
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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?
Learning Check
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