chapter 9: chemical reactions chemistry matter and change
TRANSCRIPT
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Chapter 9: Chemical ReactionsChapter 9: Chemical Reactions
CHEMISTRY Matter and Change
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Section 9.1 Reactions and Equations
Section 9.2 Classifying Chemical Reactions
Section 9.3 Reactions in Aqueous Solutions
ExitClick a hyperlink to view the corresponding slides.
CHAPTER
9 Table Of Contents
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• Recognize evidence of chemical change.
chemical change: a process involving one or more substances changing into a new substance
chemical reaction
reactant
product
chemical equation
coefficient
• Represent chemical reactions with equations.
• Balance chemical equations.
Chemical reactions are represented by balanced chemical equations.
SECTION9.1
Reactions and Equations
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• * is called a chemical reaction.
SECTION9.1
Reactions and Equations
Chemical Reactions
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• Evidence that a chemical reaction may have occurred:– *
– *
– *
– Gas bubbles
– Appearance of a solid
SECTION9.1
Reactions and Equations
Chemical Reactions (cont.)
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• Chemists use statements called equations to represent chemical reactions.
• Reactants are the *.
• Products are the *.
• This table summarizes the symbols used in chemical equations.
SECTION9.1
Reactions and Equations
Representing Chemical Reactions
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• In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”.
• Skeleton equations use symbols and formulas to represent the reactants and products.
Al(s) + Br(l) → AlBr3(s)
• Both word and skeleton equations lack information about how many atoms are involved in the reaction.
SECTION9.1
Reactions and Equations
Representing Chemical Reactions (cont.)
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• A chemical equation is a statement that uses chemical formulas to *
SECTION9.1
Reactions and Equations
Representing Chemical Reactions (cont.)
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• This figure shows the balanced equation for the reaction between aluminum and bromine.
SECTION9.1
Reactions and Equations
Balancing Chemical Equations
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• A coefficient in a chemical equation is the *.
SECTION9.1
Reactions and Equations
Balancing Chemical Equations (cont.)
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SECTION9.1
Reactions and Equations
Balancing Chemical Equations (cont.)
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SECTION9.1
Reactions and Equations
Balancing Chemical Equations (cont.)
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SECTION9.1
Reactions and Equations
Balancing Chemical Equations (cont.)
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• The most fundamental law in chemistry is the law of conservation of mass.
• Balanced equations show this law.
SECTION9.1
Reactions and Equations
Balancing Chemical Equations (cont.)
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SECTION9.1
Reactions and Equations
Balancing Chemical Equations (cont.)
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• Classify chemical reactions.
metal: an element that is a solid at room temperature, a good conductor of heat and electricity, and is generally shiny
• Identify the characteristics of different classes of chemical reactions.
SECTION9.2
Classifying Chemical Reactions
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synthesis reaction
combustion reaction
decomposition reaction
single-replacement reaction
There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.
double-replacement reaction
precipitate
SECTION9.2
Classifying Chemical Reactions
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• Chemists classify reactions in order to organize the many types.
• A synthesis reaction is a reaction in which *.
SECTION9.2
Classifying Chemical Reactions
Types of Chemical Reactions
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• When two elements react, the reaction is always a synthesis reaction.
SECTION9.2
Classifying Chemical Reactions
Types of Chemical Reactions (cont.)
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• In a combustion reaction, *
• Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.
SECTION9.2
Classifying Chemical Reactions
Types of Chemical Reactions (cont.)
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• A decomposition reaction is one in which *.
• Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.
SECTION9.2
Classifying Chemical Reactions
Decomposition Reactions
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• * is called a single replacement reaction.
A + BX → AX + B
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions
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• A metal will not always replace a metal in a compound dissolved in water because of differing reactivities.
• An activity series can be used to predict if reactions will occur.
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions (cont.)
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• Halogens frequently replace other halogens in replacement reactions.
• Halogens also have different reactivities and do not always replace each other.
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions (cont.)
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• Double replacement reactions occur when *.
• This figure shows a generic double replacement equation.
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions (cont.)
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• * is called a precipitate.
• All double replacement reactions produce either water, a precipitate, or a gas.
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions (cont.)
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• This table shows the steps to write double replacement reactions.
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions (cont.)
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• This table summarizes different ways to predict the products of a chemical reaction.
SECTION9.2
Classifying Chemical Reactions
Replacement Reactions (cont.)
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• Describe aqueous solutions.
solution: a uniform mixture that might contain solids, liquids, or gases
• Write complete ionic and net ionic equations for chemical reactions in aqueous solutions.
• Predict whether reactions in aqueous solutions will produce a precipitate, water, or a gas.
SECTION9.3
Reactions in Aqueous Solutions
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aqueous solution
solute
solvent
Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.
complete ionic equation
spectator ion
net ionic equation
SECTION9.3
Reactions in Aqueous Solutions
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• An aqueous solution contains one or more *
• The solvent is the *
SECTION9.3
Reactions in Aqueous Solutions
Aqueous Solutions
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• Water is always the solvent in an aqueous solution.
• There are many possible solutes—sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions.
• Compounds that produce hydrogen ions in aqueous solutions are acids.
SECTION9.3
Reactions in Aqueous Solutions
Aqueous Solutions (cont.)
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• Ionic compounds can also be solutes in aqueous solutions.
• When ionic compounds dissolve in water, their ions separate in a process called dissociation.
SECTION9.3
Reactions in Aqueous Solutions
Aqueous Solutions (cont.)
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• When two solutions that contain ions as solutes are combined, the ions might react.
• If they react, it is always a double replacement reaction.
• Three products can form: precipitates, water, or gases.
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions
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• Aqueous solutions of sodium hydroxide and copper(II) chloride react to form the precipitate copper(II) hydroxide.
2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s)
• * are called complete ionic equations.
2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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• * are called spectator ions and are not usually written in ionic equations.
• * are called net ionic equations.
2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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• Some reactions produce more water molecules.
• No evidence of a chemical reaction is observable.
HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq)
• Without spectator ions H+(aq) + OH–(aq) → H2O(l).
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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• Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide.
2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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• Another example is mixing vinegar and baking soda, which produces carbon dioxide gas.
HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)
• H2CO3(aq) decomposes immediately.
H2CO3(aq) → H2O(l) + CO2(g)
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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• Two reactions can be combined and represented by a single chemical reaction.
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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Reaction 1
HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq)Reaction 2
H2CO3(aq) → H2O(l) + CO2(g)
Combined equation
HCl(aq) + NaHCO3(aq) + H2CO3(aq) → H2CO3(aq) + NaCl(aq) + H2O(l) + CO2(g)
Overall equation
HCl(aq) + NaHCO3(aq) → H2O(l) + CO2(g) + NaCl(aq)
SECTION9.3
Reactions in Aqueous Solutions
Types of Reactions in Aqueous Solutions (cont.)
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Key Concepts
• Some physical changes are evidence that indicate a chemical reaction has occurred.
• Word equations and skeleton equations provide important information about a chemical reaction.
• A chemical equation gives the identities and relative amounts of the reactants and products that are involved in a chemical reaction.
• Balancing an equation involves adjusting the coefficients until the number of atoms of each element is equal on both sides of the equation.
Study Guide
SECTION9.1
Reactions and Equations
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• Classifying chemical reactions makes them easier to understand, remember, and recognize.
• Activity series of metals and halogens can be used to predict if single-replacement reactions will occur.
Study Guide
SECTION9.2
Classifying Chemical Reactions
Key Concepts
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• In aqueous solutions, the solvent is always water. There are many possible solutes.
• Many molecular compounds form ions when they dissolve in water. When some ionic compounds dissolve in water, their ions separate.
• When two aqueous solutions that contain ions as solutes are combined, the ions might react with one another. The solvent molecules do not usually react.
• Reactions that occur in aqueous solutions are double-replacement reactions.
Study Guide
SECTION9.3
Reactions in Aqueous Solutions
Key Concepts