1. Chapter 3 Chemical Reactions

2. Chemical Change Evidence Chapter 6

3. Chemical Change Evidence Chapter 6 What is a clue that a chemical reaction has occurred? a)The color changes. b)A solid forms. c)Bubbles are present. d)A flame is produced.

4. Chemical Change Evidence Chapter 6 What is a clue that a chemical reaction has occurred? “Colorless hydrochloric acid is added to a red solution of cobalt(II) nitrate, turning the solution blue.” a)The color changes. b)A solid forms. c)Bubbles are present. d)A flame is produced.

5. Chemical Change Evidence Chapter 6 What is a clue that a chemical reaction has occurred? “A solid forms when a solution of sodium dichromate is added to a solution of lead nitrate.” a)A gas forms. b)A solid forms. c)Bubbles are present. d)A flame is produced.

6. Chapter 6 Chemical Reactions A chemical equation is an abbreviated way to show a chemical or physical change A chemical change alters the physical and chemical properties of a substance Factors that indicate a chemical change  Change in color  Temperature change  Change in odor  Change in taste (we do not taste chemicals) Reactions always contain an arrow that separates the reactants from the products ReactantsProducts

7. Types of Chemical Reactions Combination reaction (synthesis)  Elements for reactants  Examples: H 2 + O 2 H 2 O N 2 + H 2 NH 3 Al + O 2 Al 2 O 3 The Law of Conservation of matter, states matter cannot be created nor destroyed, the means equations must be balanced.

8. Types of Chemical Reactions Balance the first equation H 2 + O 2 H 2 O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water

9. Types of Chemical Reactions Balance the first equation H 2 + O 2 2H 2 O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water The two now doubles everything in water, thus 4 hydrogen and 2 oxygen. Now place a 2 in front of hydrogen.

10. Types of Chemical Reactions Balance the first equation 2H 2 + O 2 2H 2 O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water The two now doubles everything in water, thus 4 hydrogen and 2 oxygen. Now place a 2 in front of hydrogen.

11. Types of Chemical Reactions Now balance the second equation N 2 + H 2 NH 3 Note two nitrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia

12. Types of Chemical Reactions Now balance the second equation N 2 + H 2 2NH 3 Note two nitrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia. This makes 2 nitrogen atoms and 6 hydrogen atoms. Now place a 3 in front of hydrogen to balance hydrogen atoms.

13. Types of Chemical Reactions Now balance the second equation N 2 + 3 H 2 2NH 3 Note two nitrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia. This makes 2 nitrogen atoms and 6 hydrogen atoms. Now place a 3 in front of hydrogen to balance hydrogen atoms.

14. Types of Chemical Reactions Decomposition Reaction  Compounds form simpler compounds or elements.  Examples H 2 OH 2 + O 2

15. Types of Chemical Reactions Decomposition Reaction  Compounds form simpler compounds or elements.  Examples 2H 2 OH 2 + O 2

16. Types of Chemical Reactions Decomposition Reaction  Compounds form simpler compounds or elements.  Examples 2H 2 O2H 2 + O 2 Notice decomposition reactions are the opposite of combination reactions

17. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound

18. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound

19. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HClZnCl + H Now make the products stable. Slide with Clyde

20. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HClZnCl 2 + H 2 Now make the products stable. Slide with Clyde

21. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HClZnCl 2 + H 2 Now make the products stable. Slide with Clyde Now Balance

22. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + 2HClZnCl 2 + H 2 Now make the products stable. Slide with Clyde Now Balance

23. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl 2 + MgBr 2 How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound. In this case we are trading nonmetals

24. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl 2 + MgBr 2 Br + MgCl How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound. In this case we are trading nonmetals

25. Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl 2 + MgBr 2 Br 2 + MgCl 2 How do we predict the products? Trade places with the metal or nonmetal with the metal or nonmetal in the compound. In this case we are trading nonmetals

26. Types of Chemical Reactions Double Replacement reactions contain compounds as reactants. HCl + Ca(OH) 2 CaCl + HOH Check formulas, and slide with Clyde when necessary

27. Types of Chemical Reactions Double Replacement reactions contain compounds as reactants. HCl + Ca(OH) 2 CaCl 2 + HOH Check formulas, and slide with Clyde when necessary

28. Types of Chemical Reactions Double Replacement reactions contain compounds as reactants. 2HCl + Ca(OH) 2 CaCl 2 + 2HOH Check formulas, and slide with Clyde when necessary Now Balance!

29. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H 2 + O 2 CH 4 + O 2 What is the oxide of hydrogen?

30. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H 2 + O 2 CH 4 +O 2 What is the oxide of hydrogen? Water

31. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H 2 + O 2 H 2 O CH 4 + O 2 What is the oxide of hydrogen? Water And the oxide of carbon?

32. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H 2 + O 2 H 2 O CH 4 + O 2 CO 2 + H 2 O What is the oxide of hydrogen? Water And the oxide of carbon? Carbon dioxide

33. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H 2 + O 2 2H 2 O CH 4 + O 2 CO 2 + H 2 O Now balance

34. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H 2 + O 2 2H 2 O CH 4 + O 2 CO 2 + 2H 2 O Now balance

35. Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H 2 + O 2 2H 2 O CH 4 + 2O 2 CO 2 + 2H 2 O Now balance

36. The Chemical Package The baker uses a package called the dozen. All dozen packages contain 12 objects. The stationary store uses a package called a ream, which contains 500 sheets of paper. So what is the chemistry package? About Packages

37. The Chemical Package The baker uses a package called the dozen. All dozen packages contain 12 objects. The stationary store uses a package called a ream, which contains 500 sheets of paper. So what is the chemistry package? Well, it is called the mole (Latin for heap). About Packages Each of the above packages contain a number of objects that are convenient to work with, for that particular discipline.

38. The atomic weights listed on the periodic chart are the weights of a mole of atoms. For example a mole of hydrogen atoms weighs 1.00797 g and a mole of carbon atoms weighs 12.01 g. The Mole A mole contains 6.022X10 23 particles, which is the number of carbon-12 atoms that will give a mass of 12.00 grams, which is a convenient number of atoms to work with in the chemistry laboratory.

39. Moles of Objects Suppose we order a mole of marshmallows for a chemistry party. How much space here at Central would be required to store the marshmallows?

40. Moles of Objects Suppose we order a mole of marshmallows for a chemistry party. How much space here at Central would be required to store the marshmallows? Would cover the entire 50 states 60 miles deep

41. Moles of Objects Suppose we order a mole of marshmallows for a chemistry party. How much space here at Central would be required to store the marshmallows? Would cover the entire 50 states 60 miles deep How about a mole of computer paper instead of a ream of computer paper, how far would that stretch?

42. Moles of Objects Suppose we order a mole of marshmallows for a chemistry party. How much space here at Central would be required to store the marshmallows? Would cover the entire 50 states 60 miles deep How about a mole of computer paper instead of a ream of computer paper, how far would that stretch? Way past the planet Pluto!

43. To calculate the molar mass of a compound we sum together the atomic weights of the atoms that make up the formula of the compound. This is called the formula weight (MW, M). Formula weights are the sum of atomic weights of atoms making up the formula. The following outlines how to find the formula weight of water symbol weight number H O 1.01 16.0 2 1 X X = =2.02 16.0 18.0 g/mole Formula Weight Calculation

44. Percent Composition Find the formula weight and the percent composition of glucose (C 6 H 12 O 6 ) symbol weightnumber H O C 16.0 1.01 12.0 6 12 6 x x x = = = 72.0 12.12 96.0 180.1 g/mole %C = %H = %O = 72.0 12.12 96.0 180.1 X = 40.0 %C 6.73 %H 53.3 %O

45. Law of Conservation of Mass The law of conservation of mass states that the sum of the masses of the reactants of a chemical equation is equal to the sum of the masses of the products.

46. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca

47. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca

48. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca 40.078 g Ca Mole Ca

49. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca 40.078 g Ca Mole Ca = 0.490 mole Ca

50. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca 40.078 g Ca Mole Ca = 0.490 mole Ca 15.0 g Cu

51. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca 40.078 g Ca Mole Ca = 0.490 mole Ca 15.0 g Cu 63.546 g Cu Mole Cu

52. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca 40.078 g Ca Mole Ca = 0.490 mole Ca 15.0 g Cu 63.546 g Cu Mole Cu 6.022X10 23 atoms Cu

53. Mole Calculations 1.How many moles of Ca atoms are present in 20.0 g of calcium? 2.How many Cu atoms are present in 15.0 g of copper? 20.0 g Ca 40.078 g Ca Mole Ca = 0.490 mole Ca 15.0 g Cu 63.546 g Cu Mole Cu 6.022X10 23 atoms Cu = 1.42X10 23 atoms Cu

54. Empirical Formulas 1.Assume there is 100 g of the sample, so the percent composition will equal the number of grams of each element. 2.Convert the grams of each element into the moles of each element with their molar mass. 3.Divide the smallest number of moles of an element into the moles of each element present. 4.Convert the fractional ratios for each element into whole numbers by multiplying all the ratios by the same number. 5.The resulting numbers are the subscripts for the each element in the empirical formula.

55. Example Asbestos was used for years as an insulating material in buildings until prolonged exposure to asbestos was demonstrated to cause lung cancer. Asbestos is a mineral containing magnesium, silicon, oxygen, and hydrogen. One form of asbestos, chrysotile (520.27 g/mol), has the composition 28.03% magnesium, 21.60% silicon, 1.16% hydrogen. Determine the empirical formula of chrysotile.

56. Molecular Formula The molecular formula can be determined from the percent composition and mass spectral data.

57. Example A combustion analysis of an unknown compound indicated that it is 92. 23% C and 7.82% H. The mass spectrum indicated the molar mass is 78 g/mol. What is the molecular formula of this unknown compound?

58. Combustion Analysis C a H b + excess O 2 ---> a CO 2 (g) + b/2 H 2 O The percent of carbon and hydrogen in C a H b can be determined from the mass of H 2 O and CO 2 produced.

59. Combustion Analysis Vitamin C is essential for the prevention of scurvy. Combustion of a 0.2000 g sample of this carbon, hyddrogen, oxygen compound yields 0.2998 g CO 2 and 0.0819 g H 2 O. What is the empirical formula of vitamin C?

60. Mass Spectrometry All Mass spectrometers separate atoms and molecules by first converting them into ions and then separating those ions based on the ratio of their masses to their electric charges. Mass spectrometers are instruments used to determine the mass of substances.

61. Mass Spectrometer

62. Mass Spectra

63. Limiting Reactants During photosynthesis a reaction mixture of carbon dioxide and water is converted to a molecule of glucose.

64. Limiting Reagents The limiting reactant is completely consumed in the chemical reaction.  The amount of product formed depends on the amount of limiting reagent available.

65. Example 10.0 g of methane (CH 4 ) is burned in 20.0 g of oxygen (O 2 ) to produce carbon dioxide (CO 2 ) and water (H 2 O). a. What is the limiting reactant? b. How many grams of water will be produced?

66. Percent Yield Theoretical Yield: the calculated amount of product formed Theoretical Yield: the calculated amount of product formed Actual Yield: the measured amount of product formed Actual Yield: the measured amount of product formed Percent Yield = Actual Yield x 100% Theoretical YieldPercent Yield = Actual Yield x 100% Theoretical Yield

67. Percent Yield Example Aluminum burns in bromine liquid producing aluminum bromide. In a certain experiment, 6.0 g of aluminum was reacted with an excess of bromine to yield 50.3 g aluminum bromide. Calculate the theoretical and percent yields for this experiment.

68. The End