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Chapter #7

Chapter #7. Chemical Reactions. CHAPTER #7 CONTENTS. 7-1 Grade School Volcanoes, Cars, & Detergents 7-2 Evidence of Chemical Reactions 7-3 The Chemical Equation 7-4 How to Write Balanced Chemical Equations 7-10 Classification of Chemical Reactions 7-9 Oxidation Reduction Reactions

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Chapter #7

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  1. Chapter #7 Chemical Reactions

  2. CHAPTER #7 CONTENTS • 7-1 Grade School Volcanoes, Cars, & Detergents • 7-2 Evidence of Chemical Reactions • 7-3 The Chemical Equation • 7-4 How to Write Balanced Chemical Equations • 7-10 Classification of Chemical Reactions • 7-9 Oxidation Reduction Reactions • 7-5 Aqueous Solutions and Solubility • 7-6 Precipitation Reactions • 7-7 Aqueous Reactions • 7-8 Acid/Base and Gas Evolution Reactions

  3. 7-2 Chemical Change Evidence Chapter 6

  4. 7-2 Chemical Change Evidence 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. Chapter 6

  5. 7-2 Chemical Change Evidence 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. Chapter 6

  6. 7-2 Chemical Change Evidence 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. Chapter 6

  7. 7-10 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 Reactants Products Chapter 6

  8. 7-10 Types of Chemical Reactions • Combination reaction (synthesis) • Elements for reactants • Examples: H2 + O2 H2O N2 + H2 NH3 Al + O2 Al2O3 The Law of Conservation of matter, states matter cannot be created nor destroyed, the means equations must be balanced.

  9. 7-10 Types of Chemical Reactions Balance the first equation H2 + O2 H2O Note two oxygen atoms on the reactant side and only one on the product side, therefore place a two in front of water

  10. 7-10 Types of Chemical Reactions Balance the first equation H2 + O22H2O 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. 7-10 Types of Chemical Reactions Balance the first equation 2H2 + O22H2O 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.

  12. 7-10 Types of Chemical Reactions Now balance the second equation N2 + H2 NH3 Note two nigrogen atoms on the reactant side and only one on the product side. Place a 2 in front of ammonia

  13. 7-10 Types of Chemical Reactions Now balance the second equation N2 + H22NH3 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. 7-10 Types of Chemical Reactions Now balance the second equation N2 + 3 H22NH3 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.

  15. 7-10 Types of Chemical Reactions • Decomposition Reaction • Compounds form simpler compounds or elements. • Examples H2OH2 + O2

  16. 7-10 Types of Chemical Reactions • Decomposition Reaction • Compounds form simpler compounds or elements. • Examples 2H2OH2 + O2

  17. 7-10 Types of Chemical Reactions • Decomposition Reaction • Compounds form simpler compounds or elements. • Examples 2H2O2H2 + O2 • Notice decomposition reactions are the opposite of combination reactions

  18. 7-10 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. 7-10 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

  20. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl ZnCl + H Now make the products stable. Slide with Clyde

  21. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl ZnCl2 + H2 Now make the products stable. Slide with Clyde

  22. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + HCl ZnCl2 + H2 Now make the products stable. Slide with Clyde Now Balance

  23. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Example: Zn + 2HCl ZnCl2 + H2 Now make the products stable. Slide with Clyde Now Balance

  24. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl2 + MgBr2 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. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl2 + MgBr2 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

  26. 7-10 Types of Chemical Reactions Single Replacement reactions have an element and a compound for reactants. Another Example: Cl2 + MgBr2 Br2 + MgCl2 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

  27. 7-10 Types of Chemical Reactions Double Replacementreactions contain compounds as reactants. HCl + Ca(OH)2 CaCl + HOH Check formulas, and slide with Clyde when necessary

  28. 7-10 Types of Chemical Reactions Double Replacementreactions contain compounds as reactants. HCl + Ca(OH)2 CaCl 2 + HOH Check formulas, and slide with Clyde when necessary

  29. 7-10 Types of Chemical Reactions Double Replacementreactions contain compounds as reactants. 2HCl + Ca(OH)2 CaCl 2 + 2HOH Check formulas, and slide with Clyde when necessary Now Balance!

  30. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 CH4 + O2 What is the oxide of hydrogen?

  31. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 CH4 + O2 What is the oxide of hydrogen? Water

  32. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 H2O CH4 + O2 What is the oxide of hydrogen? Water And the oxide of carbon?

  33. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. H2 + O2 H2O CH4 + O2 CO2 + H2O What is the oxide of hydrogen? Water And the oxide of carbon? Carbon dioxide

  34. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H2 + O22H2O CH4 + O2 CO2 + H2O Now balance

  35. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H2 + O22H2O CH4 + O2 CO2 + 2H2O Now balance

  36. 7-10 Types of Chemical Reactions Combustion Reactions occur when an element or compound combine with oxygen to produce oxides of each element. 2H2 + O22H2O CH4 + 2O2 CO2 + 2H2O Now balance

  37. 7-10 Types of Chemical Reactions REDOX reactionswhere the oxidation number changes from reactants to products. Oxidation is when the oxidation number increases, by losing of electrons. Reductionis when the oxidation numberdecreases by gaining electrons. Consider the following equation: H2 + O2 H2O What are the oxidation numbers of hydrogen and oxygen?

  38. 7-10 Types of Chemical Reactions REDOX reactionswhere the oxidation number changes from reactants to products. Oxidation is when the oxidation number increases, by losing of electrons. Reductionis when the oxidation numberdecreases by gaining electrons. Consider the following equation: H2 + O2 H2O What are the oxidation numbers of hydrogen and oxygen? 0 0

  39. 7-9 REDOX REACTIONS 0 0 2(1+) 2- = 0 H2 + O2 H2O How about hydrogen and oxygen in water?

  40. 7-9 REDOX REACTIONS 0 0 2(1+) 2- = 0 H2 + O2 H2O How about hydrogen and oxygen in water? Oxidation is caused by the oxygen molecule, so it is referred to as the oxidizing agent (OA) Reduction is caused by the hydrogen molecule, so it is referred to as the reducing agent (RA) reduced oxidized

  41. 7-9 REDOX REACTIONS Note: • All of the previously discussed reactions are REDOX except the double replacement reactions. • The number of electrons lost is equal to the number of electrons gained in a reaction. Why? • Most elements have variable oxidation numbers, except for hydrogen, oxygen, and the memorized polyatomic ions.

  42. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H+ and oxygen is 2- 1+ 4(2-)=0

  43. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H is 1+ and oxygen is 2- 1+ 7+ 4(2-)=0

  44. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H is 1+ and oxygen is 2- 1+ 7+ 4(2-)=0 5+

  45. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H is 1+ and oxygen is 2- 1+ 7+ 4(2-)=0 5+ 3+

  46. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H is 1+ and oxygen is 2- 1+ 7+ 4(2-)=0 5+ 3+ 1+

  47. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H is 1+ and oxygen is 2- 1+ 7+ 4(2-)=0 5+ 3+ 1+ 0

  48. 7-9 REDOX REACTIONS Oxidation numbers for a compound must add up to equal zero, while the oxidation numbers for a polyatomic ion must up to equal the charge of that ion. Consider the following chlorine compounds HClO4, HClO3, HClO2, HClO, Cl2, HCl What is the oxidation number of chlorine in each of these compounds, assuming H is 1+ and oxygen is 2- 1+ 7+ 4(2-)=0 5+ 3+ 1+ 0 1-

  49. 7-9 REDOX REACTIONS 3(2-)=2- How about sulfur in SO3 2-

  50. 7-9 REDOX REACTIONS 4+ 3(2-)=2- How about sulfur in SO3 2- How about carbon in C6H12O6 12(1+) +6(2-)=0

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