Chapter 7: Honors Chemistry

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Chapter 7 Honors Chemistry

• Reactions in Aqueous Solutions
• MAIN QUESTION
• What are the driving forces for a reaction

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Section 7.1 Predicting Whether a Reaction will
Occur

• Objective To learn about some of the factors
  that cause reactions to occur

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Section 7.1 Predicting Whether a Reaction will
Occur

• Why does a chemical reaction occur?
• What causes reactants to want to form products?

Driving forces
1) Formation of a solid
2) Formation of water
3) Transfer of electrons
4) Formation of a gas
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Section 7.2 Reactions in Which a Solid Forms

• Objective To learn to identify the solid that
  forms in a precipitation reaction

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Section 7.2 Reactions in Which a Solid Forms
Precipitation chemical reaction in which a solid
forms
The solid that is formed is called the
precipitate and the reaction is called a
precipitation reaction
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Section 7.2 Reactions in Which a Solid Forms
What happens when an Ionic compound Dissolves in
Water? -When a solid containing ions dissolves in
Water the ions separate and move
around Independently. -We say that the ions
dissociate PURE WATER DOES NOT CONDUCT A
CURRENT!
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Figure 7.2 Pure water does not conduct an
electric current.
Figure 8.2 When an ionic compound is dissolved
in water, current flows.
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Section 7.2 Reactions in Which a Solid Forms
Strong Electrolyte when each unit of a substance
that dissolves in water produces separated
ions Example K2CrO4 (aq) Ba(NO3)2 2K(aq)
CrO42- (aq) Ba2(aq) 2NO3- (aq)
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Section 7.2 Reactions in Which a Solid Forms
How to decide WHAT product forms? -A solid
compound must have a net zero positive
charge -Compound must contain an anion and
cation -most ionic compounds contain only 2
types of ions. CrO42- NO3- K
K2CrO4 KNO3 Ba2 BaCrO4 Ba(NO3)2
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Table 7.1
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Dissolving solutions
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Section 7.2 Practice Problems

• When an aqueous solution of barium nitrate is
  added to an aqueous solution of sodium sulfate, a
  white solid forms. Identify the white solid and
  write the balanced equation for the reaction that
  occurs.

Ba(NO3)2(aq) Na2SO4(aq) BaSO4(s) 2NaNO3(aq)
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Practice problem 2

• When an aqueous solution of lead(II)nitrate is
  added to an aqueous solution of potassium iodide,
  a yellow solid forms. Identify the yellow solid
  and write the balanced equation for the reaction
  that occurs

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Practice Problems

• Ba(NO3)2(aq) K3PO4(aq)
• Na2SO4(aq) KCl(aq)

3Ba(NO3)2(aq)2K3PO4(aq) Ba3(PO4)2 6KNO3
No reaction
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Figure 7.4 The forming of solid AgCl.
AgNO3(aq) KCl(aq)
Step 1 Write the Reactants. Step 2 Write all of
the possible forms. EXCHANGE the anions of the
salts Step3 Use solubility rules
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Section 7.3 Describing Reactions in Aqueous
Solutions

• Objective To learn to describe reactions in
  solutions by writing molecular, complete ionic
  and net ionic reactions.

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Section 7.3 Reactions in Aqueous Solutions
K2CrO4(aq) Ba(NO3)2(aq) BaCrO4(s) 2KNO3(aq)
This shows the molecular equation It shows the
complete formulas of all reactants and products.
2K(aq) CrO42-(aq) Ba2(aq) 2NO3- (aq)
Complete ionic equation
BaCrO4(s) 2K(aq) 2NO3-(aq)
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Section 7.3 Reactions in Aqueous Solutions
2K(aq) CrO42-(aq) Ba2(aq) 2NO3- (aq)
Spectator ions
BaCrO4(s) 2K(aq) 2NO3-(aq)
Net ionic equation eliminates the spectator ions
Ba2(aq) CrO42-(aq)
BaCrO4(s)
Precipitation Reaction
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Section 7.3 Practice Problems

• WRITE the balanced molecular equation, the
  balanced complete ionic equation and the balanced
  net ionic equation.
• Aqueous silver nitrate is added to aqueous sodium
  chromate to form solid silver chromate and
  aqueous sodium nitrate

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Section 7.3 Practice Problems
Molecular 2AgNO3(aq)Na2CrO4(aq)
Ag2CrO4(s) 2NaNO3(aq)
Complete ionic 2Ag 2NO3-(aq) 2Na
CrO42-(aq) Ag2CrO4(s)

2Na 2NO3-(aq)
Net ionic 2Ag(aq) CrO42-(aq)
Ag2CrO4(s)
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Section 7.3 Practice Problems

• WRITE the balanced molecular equation, the
  balanced complete ionic equation and the balanced
  net ionic equation.
• Aqueous nickel(II) nitrate is added to potassium
  carbonate to form solid nickel(II) carbonate and
  aqueous potassium nitrate.

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Section 7.3 Practice Problems
Molecular Ni(NO3)2(aq)K2CO3(aq) NiCO3(s)
2KNO3(aq)
Complete ionic Ni2 2NO3-(aq) 2K
CO32-(aq) NiCO3(s)

2K 2NO3-(aq)
Net ionic Ni2(aq) CO32-(aq) NiCO3(s)
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Section 7.4 Reactions That Form Water Acids and
Bases

• Objective To learn the key characteristics of
  the reactions between strong acids and strong
  bases.

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Section 7-4 Some History

• Acids
• Sulfuric acid and nitric acid were named when
  they were discovered in the 1300s.
• However, true understanding didnt come until the
  late 1800s.
• SVANTE ARRHENIUS (Swedish grad student in
  physics)
• -FOUND that conductivity arose from the presence
  of ions.
• -Proposed that acid is a substance that produces
  H ions (protons) when it is dissolved in water.

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Section 7-4 Strong Acids and Bases
Strong acids are strong electrolytes (completely
dissociate in water) 100 molecules of HCl 100
molecules of H Examples HCl hydrochloric
acid H2SO4 sulfuric acid
HNO3 nitric acid
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Section 7-4 Strong Acids and Bases
Base a substance that produces hydroxide Ions
(OH-) in water. Strong Bases KOH K
OH- NaOH Na OH-
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Section 7-4 Strong Acids and Bases
Base a substance that produces hydroxide Ions
(OH-) in water. Strong Bases KOH K
OH- NaOH Na OH-
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Section 7-4 Strong Acids and Bases
When a strong acid mixes with a strong base it
always produces water. Molecular
equation HCl(aq) NaOH(aq) H2O(l)
NaCl(aq) Ionic Equation H Cl- Na OH-
H2O(l)Na(aq)Cl-(aq) Net ionic equation H(aq)
OH-(aq) H2O(l)
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Section 7-4 Strong Acids and Bases
When a strong acid mixes with a strong base it
always produces water. The other product is an
ionic compound Which may precipitate or remain
dissolved. (salt).
Mixing HCl and NaOH
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Section 7.5 Reactions of Metals with Nonmetals
(Oxidation-Reduction)

• Objectives To learn the general characteristics
  of a reaction between a metal and a nonmetal.
• To understand electron transfer as a driving
  force for a chemical reaction

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Section 7.5 Oxidation-Reduction

• A reaction that involves a transfer of electrons
  is called an oxidation-reduction reaction.
• Na Cl ? Na Cl-

11e-
17e-
10e- 18 e-

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17
Cl- ion
Na ion
Na atom
Cl atom
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Section 7.5 Oxidation and Reduction

• 2Mg(s) O2(g) 2MgO(s)
• Magnesium loses 2 electrons, O gains
• Homework Self-Check Exercise 8.3

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Section 7.6 Ways to Classify Reactions

• Objective To learn various classification
  schemes for reactions.

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Section 7.6 Ways to Classify Reactions

• Double-displacement reactions (precipitation
  reactions)
• AB CD AD CB
• Acid-Base reactions (involves an H ion that ends
  up in H2O as a product)
• HCl(aq) KOH(aq) H2O(l) KCl(aq)
• Oxidation-Reduction Reaction
• 2Li(s) F2(g) 2LiF(s)

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Section 7.6 Ways to Classify Reactions

• Formation of a gas
• Zn(s) 2HCl(aq) H2(g) ZnCl2(aq)
• Oxidation-reduction reaction
• OR
• Single-replacement reactions
• A BC B AC

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Section 7.7 Classifying Reactions

• Objective To consider additional classes of
  chemical reactions.

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Section 7.7 Classifying Reactions
Combustion Reactions reactions that
involve oxygen to produce heat energy so that a
flame results. CH4(g) 2O2(g)
CO2(g)2H2O(g) Also an oxidation-reduction
reaction
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Section 7.7 Classifying Reactions
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Section 7.7 Classifying Reactions

• Other examples
• Combustion of propane (rural homes)
• C3H8(g)5O2(g) 3CO2(g) 4H2O(g)
• Combustion of gasoline(used to power cars)
• 2C8H18(l)25O2(g) 16CO2(g) 18H2O(g)
• Combustion of coal (used to generate
• electricity)
• C(s)O2(g) CO2(g)

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Section 7.7 Classifying Reactions
Synthesis Reactions(combination) a given
compound is made from simpler materials
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Section 7.7 Classifying Reactions

• Synthesis reactions that involve oxygen
• Synthesis of water 2H2(g)O2(g) 2H2O(l)
• Synthesis of carbon dioxide
• C(s) O2(g) CO2(g)
• Synthesis of nitrogen monoxide
• N2(g) O2(g) 2NO(g)
• All 3 are oxidation-reduction reactions
• The first 2 are also combustion reactions

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Section 7.7 Classifying Reactions

• Synthesis reactions that dont involve oxygen
• Synthesis of sodium chloride
• 2Na(s) Cl2(g) 2NaCl(s)
• Synthesis of magnesium fluoride
• Mg(s) F2(g) MgF2(g)
• They are also oxidation-reduction reactions.

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Section 7.7 Classifying Reactions

• Decomposition reactions a reaction in which
• a compound is broken down into simpler
• compounds. This occurs with an infusion of
• heat or electricity.
• Decomposition of water.
• 2H2O(l) 2H2(g) O2(g)
• Electric current
• Decomposition of mercury (II) oxide
• 2HgO(s) 2Hg(l) O2(g)
• Heat

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Classify the following reactionsPrecipitation,aci
d-base, oxidation-reduction
Precipitation Double-displacement

• K2SO4(aq)Ba(NO3)2 BaSO4(s)KNO3

HCl(aq)Zn(s) H2(g) ZnCl2
Ox-red Single replacement
Double displacement precipitation
HCl(aq) AgNO3(aq) HNO3(aq) AgCl(s)
HCl(aq) KOH(aq) H2O(l) KCl(aq)
Acid-base
Zn(s) CuSO4(aq) ZnSO4(aq) Cu(s)
Oxidation-reduction Single-replacement
Acid-base
NaH2PO4(aq) NaOH(aq) Na3PO4(aq)H2O(l)
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Precipitation Acid-base

• Ca(OH)2(aq)H2SO4 CaSO4(s) H2O(l)

ZnCl2(aq) Mg(s) Zn(s) MgCl2(aq)
Single-replacement Oxidation-reduction
BaCl2(aq) H2SO4(aq) BaSO4 HCl(aq)
Precipitation Double-displacement
C6H12(l) O2(g) CO2(g) H2O(g)
combustion
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Classifying additional reactions

• C3H8(l) O2(g)?CO2(g) H2O(g)

H2O2(aq)?H2O(l) O2(g)
C6H12(l) O2(g)?CO2(g) H2O(g)
HCl(aq.) AgC2H3O2(aq)?AgCl(s) HC2H3O2(aq)
HCl(aq) Al(OH)3(s)?AlCl3(aq) H2O(l)
N2H4(l) O2(g)?N2(g) H2O(g)
Cl2(g) F2(g)? ClF(g)
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Classifying reactions

• Ca(OH)2(s) HNO3(aq)?Ca(NO3)2(aq) H2O(l)

BaCl2(aq) H2SO4(aq)?BaSO4(s) HCl(aq)
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H2O2(aq)?H2O(l) O2 (g)
H2SO4(aq) Cu(s) ?CuSO4(aq) H2(g)
H2SO4(aq)NaOH(aq)?Na2SO4(aq)H2O(l)
H2SO4(aq)Ba(OH)2(aq)?BaSO4(s)H2O(l)
AgNO3(aq) CuCl2(aq)?Cu(NO3)2(aq)AgCl (s)
KOH(aq)CuSO4(aq)?Cu(OH)2(s)K2SO4(aq)
Cl2(g) F2(g)?ClF(g)
NO(g)O2(g)?NO2(g)
NaN3(s)?Na3N(s) N2(g)
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C6H12O6(s)?C(s) H2O(g)
C2H6O2(l)O2(g)?CO2(g)H2O(g)