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Chapter 9: Chemical Reactions

CHEMISTRY Matter and Change. Chapter 9: Chemical Reactions. Table Of Contents. CHAPTER 9. Section 9.1 Reactions and Equations Section 9.2 Classifying Chemical Reactions Section 9.3 Reactions in Aqueous Solutions. Click a hyperlink to view the corresponding slides. Exit.

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Chapter 9: Chemical Reactions

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  1. CHEMISTRY Matter and Change Chapter 9: Chemical Reactions

  2. Table Of Contents CHAPTER9 Section 9.1 Reactions and Equations Section 9.2 Classifying Chemical Reactions Section 9.3 Reactions in Aqueous Solutions Click a hyperlink to view the corresponding slides. Exit

  3. Reactions and Equations SECTION9.1 • Recognizeevidence of chemical change. chemical change:a process involving one or more substances changing into a new substance • Representchemical reactions with equations. • Balancechemical equations. chemical reaction reactant product chemical equation coefficient Chemical reactions are represented by balanced chemical equations.

  4. Reactions and Equations SECTION9.1 Chemical Reactions • The process by which one or more substances are rearranged to form different substances is called a chemical reaction.

  5. Reactions and Equations SECTION9.1 Chemical Reactions (cont.) • Evidence that a chemical reaction may have occurred: • Change in temperature • Change in color • Odor • Gas bubbles • Appearance of a solid

  6. Reactions and Equations SECTION9.1 Representing Chemical Reactions • Chemists use statements called equations to represent chemical reactions. • Reactantsare the starting substances. • Productsare the substances formed in the reaction. • This table summarizes the symbols used in chemical equations.

  7. Reactions and Equations SECTION9.1 Representing Chemical Reactions (cont.) • 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.

  8. Reactions and Equations SECTION9.1 Representing Chemical Reactions (cont.) • A chemical equationis a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.

  9. Reactions and Equations SECTION9.1 Balancing Chemical Equations • This figure shows the balanced equation for the reaction between aluminum and bromine.

  10. Reactions and Equations SECTION9.1 Balancing Chemical Equations (cont.) • A coefficientin a chemical equation is the number written in front of a reactant or product, describing the lowest whole-number ratio of the amounts of all the reactants and products.

  11. Reactions and Equations SECTION9.1 Balancing Chemical Equations (cont.)

  12. Reactions and Equations SECTION9.1 Balancing Chemical Equations (cont.)

  13. Reactions and Equations SECTION9.1 Balancing Chemical Equations (cont.)

  14. Reactions and Equations SECTION9.1 Balancing Chemical Equations (cont.) • The most fundamental law in chemistry is the law of conservation of mass. • Balanced equations show this law.

  15. Reactions and Equations SECTION9.1 Balancing Chemical Equations (cont.)

  16. Section Check SECTION9.1 Which of the following is NOT a chemical reaction? A.a piece of wood burning B.a car rusting C.an ice cube melting into water D.red litmus paper turning blue

  17. Section Check SECTION9.1 What is the coefficient of bromine in the equation 2Al(s) + 3Br2(l) → 2AlBr3(s)? A.1 B.2 C.3 D.6

  18. Classifying Chemical Reactions SECTION9.2 • 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.

  19. Classifying Chemical Reactions SECTION9.2 synthesis reaction combustion reaction decomposition reaction single-replacement reaction double-replacement reaction precipitate There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.

  20. Classifying Chemical Reactions SECTION9.2 Types of Chemical Reactions • Chemists classify reactions in order to organize the many types. • A synthesis reaction is a reaction in which two or more substances react to produce a single product.

  21. Classifying Chemical Reactions SECTION9.2 Types of Chemical Reactions (cont.) • When two elements react, the reaction is always a synthesis reaction.

  22. Classifying Chemical Reactions SECTION9.2 Types of Chemical Reactions (cont.) • In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light. • Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.

  23. Classifying Chemical Reactions SECTION9.2 Decomposition Reactions • A decomposition reactionis one in which a single compound breaks down into two or more elements or new compounds. • Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.

  24. Classifying Chemical Reactions SECTION9.2 Replacement Reactions • A reaction in which the atoms of one element replace the atoms of another element in a compound is called a single replacement reaction. A + BX → AX + B

  25. Classifying Chemical Reactions SECTION9.2 Replacement Reactions (cont.) • 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.

  26. Classifying Chemical Reactions SECTION9.2 Replacement Reactions (cont.) • Halogens frequently replace other halogens in replacement reactions. • Halogens also have different reactivities and do not always replace each other.

  27. Classifying Chemical Reactions SECTION9.2 Replacement Reactions (cont.) • Double replacement reactionsoccur when ions exchange between two compounds. • This figure shows a generic double replacement equation.

  28. Classifying Chemical Reactions SECTION9.2 Replacement Reactions (cont.) • The solid product produced during a chemical reaction in a solution is called a precipitate. • All double replacement reactions produce either water, a precipitate, or a gas.

  29. Classifying Chemical Reactions SECTION9.2 Replacement Reactions (cont.) • This table shows the steps to write double replacement reactions.

  30. Classifying Chemical Reactions SECTION9.2 Replacement Reactions (cont.) • This table summarizes different ways to predict the products of a chemical reaction.

  31. Section Check SECTION9.2 Which of the following is NOT one of the four types of reactions? A.deconstructive B.synthesis C.single replacement D.double replacement

  32. Section Check SECTION9.2 The following equation is what type of reaction? KCN(aq) + HBr(aq) → KBr(aq) + HCN(g) A.deconstructive B.synthesis C.single replacement D.double replacement

  33. Reactions in Aqueous Solutions SECTION9.3 • Describe aqueous solutions. • 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. solution: a uniform mixture that might contain solids, liquids, or gases

  34. Reactions in Aqueous Solutions SECTION9.3 aqueous solution solute solvent complete ionic equation spectator ion net ionic equation Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.

  35. Reactions in Aqueous Solutions SECTION9.3 Aqueous Solutions • An aqueous solutioncontains one or more dissolved substances (called solutes) in water. • The solvent is the most plentiful substance in a solution.

  36. Reactions in Aqueous Solutions SECTION9.3 Aqueous Solutions (cont.) • 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.

  37. Reactions in Aqueous Solutions SECTION9.3 Aqueous Solutions (cont.) • Ionic compounds can also be solutes in aqueous solutions. • When ionic compounds dissolve in water, their ions separate in a process called dissociation.

  38. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions • 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.

  39. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) • 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) • Ionic equations that show all of the particles in a solution as they actually exist are called complete ionic equations. 2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)

  40. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) • Ions that do not participate in a reaction are called spectator ionsand are not usually written in ionic equations. • Formulas that include only the particles that participate in reactions are called net ionic equations. 2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)

  41. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) • 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).

  42. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) • Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide. 2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)

  43. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) • 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)

  44. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) • Two reactions can be combined and represented by a single chemical reaction.

  45. Reactions in Aqueous Solutions SECTION9.3 Types of Reactions in Aqueous Solutions (cont.) 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)

  46. Section Check SECTION9.3 What is the solvent in an aqueous solution? A.hydrogen B.sodium ions C.water D.alcohol

  47. Section Check SECTION9.3 An equation that includes only the particles that participate in a reaction is called: A.net ionic equation B.spectator ions C.complete ionic equation D.reduced ionic equation

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