2. Chapter Menu Chemical Reactions Section 9.1Section 9.1Reactions and Equations Section 9.2Section 9.2 Classifying Chemical Reactions Section 9.3Section 9.3 Reactions in Aqueous Solutions Exit Click a hyperlink or folder tab to view the corresponding slides.

3. Section 9-1 Section 9.1 Reactions and Equations 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.

4. Section 9-1 Chemical Reactions The process by which one or more substances are rearranged to form different substances is called a chemical reaction.chemical reaction Evidence of a chemical reaction –Change in temperature (hot or cold) –Change in color (but not from dilution or mixing of colored solutions) –Odor, gas, or bubbles may form. –Formation of a precipitate (solid from two liquids)

5. Section 9-1 Representing Chemical Reactions Chemists use statements called equations to represent chemical reactions. Reactants are the starting substances.Reactants Products are the substances formed in the reaction.Products Reactants  Products

6. This table summarizes the symbols used in chemical equations.

7. 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) → AlBr 3 (s) Skeleton equations lack information about how many atoms are involved in the reaction.

8. Representing Chemical Reactions (cont.) A chemical equation is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.chemical equation

9. Balancing Chemical Equations (cont.) A coefficient in 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.coefficient The most fundamental law in chemistry is the law of conservation of mass. Balanced equations show this law.

10. Describing Equations n Describing Coefficients:  individual atom = “atom”  covalent substance = “molecule”  ionic substance = “unit” 3 molecules of carbon dioxide 2 atoms of magnesium 4 units of magnesium oxide 3CO 2  2Mg  4MgO 

11. Balancing Chemical Equations This figure shows the balanced equation for the reaction between aluminum and bromine.

12. Balancing Steps Write the unbalanced equation. Count atoms on reactant side. Count atoms on product side. Add coefficients to make #s equal. Coefficient  subscript = # of atoms Reduce coefficients to lowest whole # ratio, if necessary. Double check your work!!!

13. Helpful Tips Balance one element at a time. Update ALL atom counts after adding a coefficient. If an element appears more than once per side, balance it last. Balance polyatomic ions as single units. –“1 SO 4 ” instead of “1 S” and “4 O”

14. Al + CuCl 2  Cu + AlCl 3 Al Cu Cl 1 1 1 1 2 3 2  3  6   3 33 2 Balancing Example Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2  2  6

15. Section 9-1 Balancing Chemical Equations (cont.)

16. Balance the following:

17. A.A B.B C.C D.D Section 9-1 Section 9.1 Assessment 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

18. A.A B.B C.C D.D Section 9-1 Section 9.1 Assessment What is the coefficient of bromine in the equation 2Al(s) + 3Br 2 (l) → 2AlBr 3 (s)? A.1 B.2 C.3 D.6

19. End of Section 9-1

20. Section 9-2 Section 9.2 Classifying Chemical Reactions 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.

21. Section 9-2 Section 9.2 Classifying Chemical Reactions (cont.) 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

22. Section 9-2 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.synthesis reaction

23. Section 9-2 Types of Chemical Reactions (cont.) In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light.combustion reaction Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.

24. The burning of any substance in O 2 to produce heat Reactants  Products Metal + Oxygen = Oxide of the metal Nonmetal + Oxygen = Oxide of the nonmetal Compound + Oxygen = Two or more oxides A + O 2  AO Types of Chemical Reactions (cont.)

25. Section 9-2 Decomposition Reactions A decomposition reaction is one in which a single compound breaks down into two or more elements or new compounds.decomposition reaction Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur. AB  A + B

26. Section 9-2 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.single replacement reaction Metals replace metals (and Hydrogen) Nonmetals replace nonmetals (usually group 17) A + BX → AX + B

27. Section 9-2 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.

28. Section 9-2 Replacement Reactions (cont.) Double replacement reactions occur when ions exchange between two compounds.Double replacement reactions

29. Section 9-2 Replacement Reactions (cont.) The solid product produced during a chemical reaction in a solution is called a precipitate. precipitate All double replacement reactions produce either water, a precipitate, or a gas.

30. Section 9-2 Replacement Reactions (cont.)

31. Section 9-2 Replacement Reactions (cont.) Synthesis = A + B  AB Combustion = A + O2  AO Decomposition = AB  A + B Single-Replace = A + BX  AX + B Double-Replace = AX + BY  AY + BX

32. A.A B.B C.C D.D Section 9-2 Section 9.2 Assessment Which of the following is NOT one of the four types of reactions? A.deconstructive B.synthesis C.single replacement D.double replacement

33. A.A B.B C.C D.D Section 9-2 Section 9.2 Assessment 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

34. End of Section 9-2

35. Section 9-3 Section 9.3 Reactions in Aqueous Solutions 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.

36. Section 9-3 Section 9.3 Reactions in Aqueous Solutions (cont.) 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

37. Section 9-3 Aqueous Solutions An aqueous solution contains one or more dissolved substances (called solutes) in water.aqueous solution solutes The solvent is the most plentiful substance in a solution.solvent

38. Section 9-3 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.

39. Section 9-3 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.

40. Section 9-3 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.

41. Section 9-3 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) + CuCl 2 (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. complete ionic equations 2Na + (aq) + 2OH – (aq) + Cu 2+ (aq)+ 2Cl – (aq) → 2Na + (aq) + 2Cl – (aq) + Cu(OH) 2 (s)

42. Section 9-3 Types of Reactions in Aqueous Solutions (cont.) Ions that do not participate in a reaction are called spectator ions and are not usually written in ionic equations.spectator ions Formulas that include only the particles that participate in reactions are called net ionic equations.net ionic equations 2OH – (aq) + Cu 2+ (aq) → Cu(OH) 2 (s)

43. Section 9-3 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) → H 2 O(l) + NaBr(aq) Without spectator ions H + (aq) + OH – (aq) → H 2 O(l).

44. Section 9-3 Types of Reactions in Aqueous Solutions (cont.) Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide. 2HI(aq) + Li 2 S(aq) → H 2 S(g) + 2LiI(aq)

45. Section 9-3 Types of Reactions in Aqueous Solutions (cont.) Another example is mixing vinegar and baking soda, which produces carbon dioxide gas. HCl(aq) + NaHCO 3 (aq) → H 2 CO 3 (aq) + NaCl(aq) H 2 CO 3 (aq) decomposes immediately. H 2 CO 3 (aq) → H 2 O(l) + CO 2 (g)

46. Section 9-3 Types of Reactions in Aqueous Solutions (cont.) Two reactions can be combined and represented by a single chemical reaction.

47. Section 9-3 Types of Reactions in Aqueous Solutions (cont.) Reaction 1 HCl(aq) + NaHCO 3 (aq) → H 2 CO 3 (aq) + NaCl(aq) Reaction 2 H 2 CO 3 (aq) → H 2 O(l) + CO 2 (g) Combined equation HCl(aq) + NaHCO 3 (aq) + H 2 CO 3 (aq) → H 2 CO 3 (aq) + NaCl(aq) + H 2 O(l) + CO 2 (g) Overall equation HCl(aq) + NaHCO 3 (aq) → H 2 O(l) + CO 2 (g) + NaCl(aq)

48. A.A B.B C.C D.D Section 9-3 Section 9.3 Assessment What is the solvent in an aqueous solution? A.hydrogen B.sodium ions C.water D.alcohol

49. A.A B.B C.C D.D Section 9-3 Section 9.3 Assessment 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

50. End of Section 9-3

51. Resources Menu Chemistry Online Study Guide Chapter Assessment Standardized Test Practice Image Bank Concepts in Motion

52. Study Guide 1 Section 9.1 Reactions and Equations 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.

53. Study Guide 2 Section 9.2 Classifying Chemical Reactions Key Concepts 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.

54. Study Guide 3 Section 9.3 Reactions in Aqueous Solutions Key Concepts 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.

55. A.A B.B C.C D.D Chapter Assessment 1 The law of conservation of mass requires what in a chemical reaction equation? A.both sides of the equation to contain the same substances B.the reactants to have the same amount of molecules as the products C.both sides to have the same amount of atoms of each element D.the products to have fewer molecules than the reactants

56. A.A B.B C.C D.D Chapter Assessment 2 A reaction that gives off heat is what type of reaction? A.single replacement reaction B.double replacement reaction C.synthesis reaction D.combustion reaction

57. A.A B.B C.C D.D Chapter Assessment 3 Ions that are present in a solution and do not participate in a chemical reaction when another substance is added are called ____. A.spectator ions B.reactants C.products D.net ions

58. A.A B.B C.C D.D Chapter Assessment 4 A double replacement reaction produces all of the following except ____. A.gases B.solids C.light D.water

59. A.A B.B C.C D.D Chapter Assessment 5 What type of reaction is the following? 2H 2 O(l) + energy → H 2 (g) + O 2 (g) A.synthesis reaction B.decomposition reaction C.combustion reaction D.replacement reaction

60. A.A B.B C.C D.D STP 1 What type of reaction is the following? 2H 2 (g) + O 2 (g) → 2H 2 O(l) A.replacement reaction B.synthesis C.combustion reaction D.double replacement reaction

61. A.A B.B C.C D.D STP 2 A precipitate forms in a double replacement reaction only if: A.the reactivities of the compounds differ B.the new compound is denser than water C.the new compound is soluble in water D.the new compound is not soluble in water

62. A.A B.B C.C D.D STP 3 A ____ is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction. A.word equation B.skeleton equation C.chemical equation D.balanced equation

63. A.A B.B C.C D.D STP 4 Predict the type of reaction. LiBr 2 (aq) + 2NaOH (aq) → ____ A.synthesis reaction B.combustion reaction C.single replacement reaction D.double replacement reaction

64. A.A B.B C.C D.D STP 5 Which reactions are essentially the opposite of synthesis reactions? A.single-replacement B.decomposition C.combustion D.double-replacement

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78. CIM Table 9.2 Steps for Balancing Equations Figure 9.15 The Forming of a Precipitate Table 9.4 Types of Chemical Reactions

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