Chapters 3 & 4 Balancing and RX Types. Chapters 3 & 4 Table of Contents Copyright © Cengage...

Chapters 3 & 4

Balancing and RX Types

Chapters 3 & 4

Table of Contents

Copyright © Cengage Learning. All rights reserved 2

3.7 Chemical Equations

3.8 Balancing Chemical Equations

4.5 Precipitation Reactions

4.6 Describing Reactions in Solution

4.4 Types of Chemical Reactions

Section 3.7

Chemical Equations

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1. To learn the signals or evidences that show a chemical reaction may have occurred

2. To learn to identify the characteristics of a chemical reaction

3. To learn the information given by a chemical equation

Objectives

Section 3.7

Chemical Equations

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Section 3.7

Chemical Equations

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1. Whoosh

2. Can You Identify any Evidences of a Chemical Reaction?

Section 3.7

Chemical Equations

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• Physical states of compounds are often given in a chemical equation.

Section 3.7

Chemical Equations

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• Chemical reactions involve a rearrangement of the ways atoms are grouped together.

• A chemical equation represents a chemical reaction. – Reactants are shown to the left of an arrow. – Products are shown to the right of the arrow.

Section 3.7

Chemical Equations

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• Let’s use all of your skills to write a reaction equation to describe the following:

• Solid Carbon reacts with gaseous oxygen to form gaseous carbon dioxide.

• Solid Mercury (II) oxide decomposes to produce elemental mercury metal and gaseous oxygen.

• Solid zinc is added to an aqueous solution of hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water.

Section 3.7

Chemical Equations

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The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical reaction.

Plop, Plop, Fizz, Fizz…..

A chemical reaction involves the rearrangement of atoms to form new substances. (Coins)

The Law of Conservation of Mass

Section 3.7

Chemical Equations

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• In a chemical reaction atoms are not created or destroyed.

• All atoms present in the reactants must be accounted for in the products. (magnets)– Same number of each type atom on both sides of arrow

___CH4 ___O2 ___CO2 ___H2O

Section 3.8

Balancing Chemical Equations

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Section 3.7

Chemical Equations

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1. To learn the signals or evidences that show a chemical reaction may have occurred

2. To learn to identify the characteristics of a chemical reaction

3. To learn the information given by a chemical equation

4. Work Session: page 116 # 7,10

5. Video of Various Chemical Rx’s Ch 7(Silver I)

Objectives Review

Section 3.8


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1. To learn to write a balanced equation for a chemical reaction

2. Are you ready??

Objectives

Section 3.8


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• A representation of a chemical reaction:

C2H5OH + 3O2 2CO2 + 3H2O

reactants products• Reactants are only placed on the left side

of the arrow, products are only placed on the right side of the arrow.

• The equation is balanced because all atoms present in the reactants are accounted for in the products.

• The balanced equation represents an overall ratio of reactants and products, not what actually “happens” during a reaction.

Section 3.8


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• A chemical reaction is balanced by using a systematic approach:

– Atoms (mass) are always conserved

– Can only change the coefficients

– Balance by trial and error starting with the most complicated molecule(s)

– At the end check to be sure the equation is balanced (same numbers of all types of atoms on the reactant and product sides)

Section 3.8


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Example: Hydrogen gas and oxygen gas combine to form liquid water.

– Write the formulas of the reactants and products to give the unbalanced chemical equation.

___H2(g) + ___O2(g) ___H2O(l)

Section 3.8


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• A chemical reaction is balanced by using a systematic approach: (Patch’s Interpretation)

– Make Sure you have the equation written correctly and leave spaces in front of each compound formula.

– Use a pencil and don’t be afraid of erasing!

– Make sure you are NOT violating the Law of Conservation of Mass!!

Section 3.8


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More Examples:

___K + ___H2O ___H2 + ___KOH

___CH4 + ___O2 ___ CO2 + ___H2O

___C2H5OH + ___O2 ___ CO2 + ___H2O

___N2 + ___H2 ___ NH3

___O2 ___ O3

___C3H8 + ___O2 ___ CO2 + ___H2O

___HF + ___SiO2 ___ SiF4 + ___H2O

___NH3 + ___O2 ___ NO + ___H2O

Section 3.8


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Independent practice:

___NH4NO2 ___N2 + ___H2O

___NO ___ N2O + ___NO2

___HNO3 ___NO2 + ___ H2O + ___O2

–What is the sum of the coefficients for each equation?

Section 3.8


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Concept Check

Which of the following are true concerning balanced chemical equations? There may be more than one true statement.I. The number of molecules is conserved.II. The coefficients tell you how much of each

substance you have.III. Atoms are neither created nor destroyed.IV. The coefficients indicate the mass ratios of the

substances used.V.The sum of the coefficients on the reactant side

equals the sum of the coefficients on the product side.

Section 3.8


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1. To learn to write a balanced equation for a chemical reaction

2. Work Session:

Page 120 # 83,84

Objectives Review

Section 4.5

Precipitation Reactions


1. To learn to identify the solid that forms in a Double Replacement precipitation reaction

2. To learn to write:

molecular,

complete ionic, and

net ionic equations .

Objectives for Sections 4.5 and 4.6

Section 4.5



• A double displacement (replacement) reaction is a reaction in which a solid forms and separates from the solution. When ionic compounds dissolve in

water (dissociation), the resulting solution contains the separated ions.

Precipitate – the solid that forms.

Section 4.5



Reactions in Which a Solid Forms

What Happens When an Ionic Compound Dissolves in • Water? VIDEO (Chapter 8 Dissolution of a solid in a liquid)

• K2CrO4(aq) + Ba(NO3)2(aq) Products

• Dissociation

Section 4.5



• Determine the possible products from the ions in the reactants.

• In our example

K2CrO4(aq) + Ba(NO3)2(aq) Products

The possible ion combinations are


How to Decide What Products Form

Section 4.5




How to Decide What Products Form

• Decide which is most likely to be the yellow solid formed in the reaction.

• K2CrO4(aq) + Ba(NO3)2(aq) Products• The possible combinations are KNO3 and BaCrO4.

– KNO3 white solid

– BaCrO4 yellow solid

Section 4.5



Precipitation of Silver Chloride

Section 4.5



Pattern for a Double Replacement Reaction (DRR)

• AB + CD AD + CB • K2CrO4(aq) + Ba(NO3)2(aq) KNO3 + BaCrO4

• Reaction will only occur if at least ONE of the products is INSOLUBLE. (Precipitate)

Section 4.5



• Soluble – solid dissolves in solution; (aq) is used in reaction.

• Insoluble – solid does not dissolve in solution; (s) is used in reaction.

• Insoluble and slightly soluble are often used interchangeably.

Precipitates

Section 4.5



1. Most nitrate (NO3) salts are soluble.

2. Most alkali metal (group 1A) salts and NH4+ are

soluble.

3. Most Cl, Br, and I salts are soluble (except Ag+, Pb2+, Hg2

2+).

4. Most sulfate salts are soluble (except BaSO4, PbSO4, Hg2SO4, CaSO4).

5. Most OH are only slightly soluble (NaOH, KOH are soluble, Ba(OH)2, Ca(OH)2 are marginally soluble).

6. Most S2, CO32, CrO4

2, PO43 salts are only slightly

soluble, except for those containing the cations in Rule 2.

Simple Rules for Solubility (Table 4.1 pg 144)

Section 4.5



Concept Check

Which of the following ions form compounds with Pb2+ that are generally soluble in water?

a) S2–

b) Cl–

c) NO3–

d) SO42–

e) Na+

Section 4.5




Section 4.5



Describing Reactions in Aqueous Solutions

• Patch’s Interpretation:

• 1 - Dance Partner Swap

• 2 - Gangster Switch

• 3 - Balance Equation

• 4 – Predict Solubility

Section 4.5



Practice Predicting Products and if Reaction Will Occur

• ___Pb(NO3)2 + ___KI

• ___AgNO3 + ___KCl

• ___KNO3 + ___BaCl2

• ___Na2SO4 + ___Pb(NO3)2

• ___KOH + ___Fe(NO3)3

• ___Ba(NO3)2 + ___NaCl

• ___Na2S + ___Cu(NO3)2

• ___NH4Cl + ___Pb(NO3)2

Describing Reactions in SolutionSection 4.6


• Gives the overall reaction stoichiometry but not necessarily the actual forms of the reactants and products in solution.

• Reactants and products generally shown as compounds.

• Use solubility rules to determine which compounds are aqueous and which compounds are solids.

AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

Formula Equation (Molecular Equation)



• Represents as ions all reactants and products that are strong electrolytes.

Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq)

AgCl(s) + Na+(aq) + NO3

(aq)

Complete Ionic Equation



• Includes only those solution components undergoing a change. Show only components that actually react

(precipitate).

Ag+(aq) + Cl(aq) AgCl(s)

Ag+(aq) + NO3(aq) + Na+(aq) + Cl(aq)

AgCl(s) + Na+(aq) + NO3

(aq)

• Spectator ions are not included (ions that do not participate directly in the reaction). Na+ and NO3

are spectator ions. (stay ions)

Net Ionic Equation

Section 4.5



• Ba2+(aq) + CrO42–(aq) → BaCrO4(s)

The Reaction of K2CrO4(aq) and Ba(NO3)2(aq)(net ionic)

Section 4.5



Write the Complete and Net Ionic Equations for each

• ___Pb(NO3)2 + ___KI

• ___AgNO3 + ___KCl

• ___KNO3 + ___BaCl2

• ___Na2SO4 + ___Pb(NO3)2

• ___KOH + ___Fe(NO3)3

• ___Ba(NO3)2 + ___NaCl

• ___Na2S + ___Cu(NO3)2

• ___NH4Cl + ___Pb(NO3)2

Section 4.5



1. To learn about some of the factors that cause reactions to occur

2. To learn to identify the solid that forms in a Double Replacement precipitation reaction

3. To learn to write:molecular, complete ionic, andnet ionic equations

1. Work Session: pg 172 #35, 37, 39, 41, 432. Dig Copy of Soly Table

Objectives Review for Sections 4.5 and 4.6

Section 4.4

Types of Chemical Reactions

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Objectives

• To learn how to identify the following types of reactions:

1. Double Replacement

2. Single Replacement

3. Acid- Base

4. Combustion

5. Synthesis

6. Decomposition vs Dissociation

Section 4.4


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Double Replacement Reactions

• AB + CD AD + CB

• Dance Partner Swap

• __KCl + __AgNO3 ___AgCl +___KNO3

Section 4.4


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Single Replacement Reactions

• A + BC AC + B

• One Cation cuts in on the Dance

• ___Zn + ___HCl ___H2 + ___ZnCl2

Section 4.4


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Single Replacement Reactions

• Driving forces for a reaction:

– Transfer of electrons

– Formation of a Gas

• A + BC B + AC

• Single replacement reaction

Section 4.4


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Acid – Base Reactions

Arrhenius Acids

• A strong acid is one in which virtually every molecule dissociates (ionizes) in water to an H+ ion and an anion.

Section 4.4


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• A strong base is a metal hydroxide that is completely soluble in water, giving separate OH ions and cations.


Arrhenius Bases

– Most common NaOH, KOH

Section 4.4


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• Acid + Base Salt + Water (DHM)

• H __ + __OH __ __ + H2O

• ___HCl + ___NaOH ___NaCl + ___H2O

• ___HCl + ___KOH ___KCl + ___H2O

• ___HNO3 + ___KOH

Section 4.4


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Combustion Reactions

__C(S) + __O2 __CO2 + Energy

Section 4.4


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Combustion Reaction of Hydrocarbons

• CxHy + O2 CO2 + H2O + Energy

• Exothermic Endothermic

• __CH4 + __O2 __CO2 + __H2O + Energy

• __C3H8 + __O2 __CO2 + __H2O + Energy

• __C8H18 + __O2 __CO2 + __H2O + Energy

• __C(S) + __O2 __CO2 + Energy

• __H2 + __O2 __H2O + Energy

• Involve oxygen and produce energy so rapidly that a flame results (Spontaneous)

Section 4.4


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Combustion Reactions

• Silly String

• NOS Nitrous Oxide Systems N2O- Injects more Oxygen into engine to allow for more fuel to be injected, making the combustion reaction faster, thereby producing more power.

• Also used medically as an anesthetic.

Section 4.4


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• A synthesis reaction is one in which a compound forms from simpler materials.

– A + B AB

– C(s) + O2(g) CO2(g) + Energy

– ___Na + ___Cl2 ___NaCl

– ___Mg + ___F2 ___MgF2

Synthesis (combination) Reactions

Section 4.4


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• A decomposition reaction occurs when a compound is broken down into simpler substances.

– AB A + B

– 2H2O(l) 2H2(g) + O2(g)

– ___HgO ___Hg + ___O2

– ___NaCl ___Na + ___Cl2– Versus Dissociation??!!

Decomposition Reactions

Section 4.4


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• The ions separate and move around independently. VIDEO • Dissociation (Chapter 8 Dissolution of a solid in a liquid)

Dissociation

What Happens When an Ionic Compound Dissolves in

Water?

Section 4.4


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• Dissociation occurs when a compound is broken down into its Ionic Components.

– AB A+ + B-

– __K2CrO4(s) __K+(aq) +__CrO4

-2(aq)

– __Ba(NO3)2(s) __Ba+2(aq) +__NO3

-1(aq)

– __Pb(NO3)2(s) __Pb+2(aq) +__NO3

-1(aq)

– __KI(s) __K+(aq) +__I-1

(aq)

Dissociation

Section 4.4


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Reactions of Metals with Nonmetals (Oxidation-Reduction)

• Reactions between metals and nonmetals involve a transfer of electrons from the metal to the nonmetal forming Ionic Compounds.– oxidation – reduction reaction

Section 4.4


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Reactions Between Metals (Oxidation-Reduction)

• Reactions between metals can involve a transfer of electrons. (Potato Clock)

– Transfer of electrons = oxidation – reduction reaction

Section 4.4


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Practice Identifying Reaction Types

• ___K + ___Cl2 ___KCl

• ___Fe2O3 + ___Al ___Al2O3 + ___Fe

• __K2CrO4 + __Ba(NO3)2 __KNO3 + __BaCrO4

• ___HCl + ___KOH ___KCl + ___H2O

• ___Mg + ___O2 ___MgO + Energy

• ___PbO2 ___Pb + ___O2

• ___Ba(NO3)2(s) ___Ba+2(aq) +___NO3

-1(aq)

• ___KBr + ___AgNO3 ___AgBr +___KNO3

• ___HNO3 +__NaOH ___H2O+___NaNO3

Section 4.4


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Objectives Review• To learn how to identify the following types of

reactions:

1. Double Replacement

2. Single Replacement

3. Acid- Base

4. Combustion

5. Synthesis

6. Decomposition vs Dissociation

7. Work Session: Page 120 # 81as instructed, 83-86 identify the reaction type ONLY.

Section 4.4


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• Do you observe any signs that a reaction has or has not occurred?

• #2 Na2CO3

• CaCl2 Cu(NO3)2

• CaCl2 + Na2CO3 ______ + _______

• Na2CO3 + Cu(NO3)2 ______ + _______

• CaCl2 + Cu(NO3)2 ______ + _______

Section 4.5



Describing Reactions in Aqueous Solutions

• Three types of equations:– Molecular (formula) equation complete formulas of all reactants and products– Complete ionic equation

all strong electrolytes are shown as ions– Net ionic equation only those components of the solution that undergo a

change• Spectator ion (those that remain unchanged)

not shown in the net ionic equation

Chapters 3 & 4 Balancing and RX Types. Chapters 3 & 4 Table of Contents Copyright © Cengage...

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