Ch. 8 Chemical Equations And Reactions

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Ch. 8 Chemical Equations And Reactions

  1. 1. Chemical Equations and Reactions CHAPTER 8
  2. 2. What is a chemical equation?
  3. 3. List and describe some indications of an occurrence of a chemical reaction.
  4. 4. List and describe some indications of an occurrence of a chemical reaction. <ul><li>Evolution of energy as heat and light </li></ul><ul><li>Production of a gas </li></ul><ul><li>Formation of a precipitate </li></ul><ul><li>Color change </li></ul>
  5. 5. List and describe some characteristics of chemical equations.
  6. 6. List and describe some characteristics of chemical equations. <ul><li>The equation must represent known facts </li></ul><ul><li>The equation must contain the correct formulas for the reactants and products </li></ul><ul><li>The law of conservation of mass must be satisfied </li></ul>
  7. 7. What does the arrow,  , signify?
  8. 8. How do you read the equation with an arrow?
  9. 9. How do you balance a chemical equation?
  10. 10. What does it mean when a chemical reaction is reversible? Give an example.
  11. 11. Symbols and Explanations <ul><li>(s) </li></ul><ul><li>(aq) </li></ul><ul><li>(l) </li></ul><ul><li>(g) </li></ul>
  12. 12. Symbols and Explanations <ul><li> </li></ul><ul><li> OR </li></ul><ul><li> </li></ul><ul><li> or  </li></ul>heat
  13. 13. Reaction in a Bag Lab Overview <ul><li>2 reactants </li></ul><ul><ul><li>CaCl 2 (calcium chloride) </li></ul></ul><ul><ul><li>NaHCO 3 (sodium bicarbonate) </li></ul></ul><ul><ul><li>Exothermic reactions gives off heat </li></ul></ul><ul><ul><li>(feels hot) </li></ul></ul><ul><ul><li>Endothermic reaction takes in heat </li></ul></ul><ul><ul><li>(feels cool) </li></ul></ul>
  14. 14. Reaction in a Bag Lab Overview <ul><ul><li>CaCl 2 </li></ul></ul><ul><ul><li>(calcium chloride) </li></ul></ul><ul><ul><li>NaHCO 3 </li></ul></ul><ul><ul><li>(sodium bicarbonate) AKA baking soda </li></ul></ul><ul><ul><li>Universal indicator and vinegar </li></ul></ul>
  15. 15. Reaction in a Bag Lab Overview <ul><li>Describe some indications that a chemical reaction occurred. </li></ul>
  16. 16. Reaction in a Bag Lab Overview <ul><li>Color change </li></ul><ul><li>Gas produced </li></ul><ul><li>(might smell the gas or see bubbles) </li></ul><ul><li>Temperature change </li></ul>
  17. 17. Elements that Normally Exist as Diatomic Molecules <ul><li>Hydrogen </li></ul><ul><li>Nitrogen </li></ul><ul><li>Oxygen </li></ul><ul><li>Fluorine </li></ul><ul><li>Chlorine </li></ul><ul><li>Bromine </li></ul><ul><li>Iodine </li></ul>
  18. 18. Which element exists as a liquid? <ul><li>Which element exists as a solid at room temperature? </li></ul>
  19. 19. Significance of a Chemical Equation <ul><li>The coefficients of a chemical reaction indicates relative, not absolute, amounts of reactants and products </li></ul><ul><li>H 2 (g) + Cl 2 (g)  2HCl(g) </li></ul>
  20. 20. Significance of a Chemical Equation <ul><li>The relative masses of the reactants and products of a chemical reaction can be determined from the reaction’s coefficients </li></ul><ul><li>H 2 (g) + Cl 2 (g)  2HCl(g) </li></ul><ul><li>Convert from moles to grams </li></ul><ul><li>IOW: 1 molecule H 2 = 1 mol H 2 = 2.02 g H 2 </li></ul>
  21. 21. Significance of a Chemical Equation <ul><li>The reverse reaction for a chemical equation has the same relative amounts of substances as the forward reaction </li></ul><ul><li>Law of conservation of mass </li></ul>
  22. 22. Balancing Chemical Equations <ul><li>Identify the names of the reactants and the products, and write a word equation </li></ul>
  23. 23. Balancing Chemical Equations <ul><li>2) Write a formula equation by substituting correct formulas for the names of the reactants and products </li></ul>
  24. 24. Balancing Chemical Equations <ul><li>3) Balance the formula equation according to the law of conservation of mass using coefficients </li></ul>
  25. 25. Balancing Chemical Equations <ul><li>4) CHECK! Count atoms to be sure that the equation is balanced. </li></ul>
  26. 26. Chemical Equation <ul><li>CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O(g) </li></ul>
  27. 27. Try this… <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Hydrogen peroxide in an aqueous solution decomposes to produce oxygen and water </li></ul>
  28. 28. Try this…(SOLUTION) <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Hydrogen peroxide in an aqueous solution decomposes to produce oxygen and water </li></ul><ul><li>Hydrogen peroxide  oxygen + water </li></ul><ul><li>2H 2 O 2 (aq)  O 2 (g) + 2H 2 O(l) </li></ul>
  29. 29. Try this… <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Solid copper metal reacts with aqueous silver nitrate to produce solid silver metal and aqueous copper nitrate </li></ul>
  30. 30. Try this…(SOLUTION) <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Solid copper metal reacts with aqueous silver nitrate to produce solid silver metal and aqueous copper nitrate </li></ul><ul><li>Copper + silver nitrate  silver + copper nitrate </li></ul><ul><li>Cu(s) + 2AgNO 3 (aq)  2Ag(s) + Cu(NO 3 ) 2 (aq) </li></ul>
  31. 31. Try this… <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Solid zinc metal reacts with aqueous copper sulfate to produce solid copper metal and aqueous zinc sulfate </li></ul>
  32. 32. Try this…(SOLUTION) <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Solid zinc metal reacts with aqueous copper sulfate to produce solid copper metal and aqueous zinc sulfate </li></ul><ul><li>Zinc + copper sulfate  copper + zinc sulfate </li></ul><ul><li>Zn(s) + CuSO 4 (aq)  Cu(s) + ZnSO 4 (aq) </li></ul>
  33. 33. Try this… <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Solid sodium oxide is added to water at room temperature and forms sodium hydroxide (dissolved in water). </li></ul><ul><li>INCLUDE PHYSICAL STATES </li></ul>
  34. 34. Try this… SOLUTION <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>Solid sodium oxide is added to water at room temperature and forms sodium hydroxide (dissolved in water). </li></ul><ul><li>INCLUDE PHYSICAL STATES </li></ul><ul><li>Sodium oxide + water  sodium hydroxide </li></ul><ul><li>Na 2 O(s) + H 2 O(l)  NaOH(aq) </li></ul>
  35. 35. Try this… <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>The reaction of zinc with aqueous hydrochloric acid produces a solution of zinc chloride and hydrogen gas. </li></ul>
  36. 36. Try this… SOLUTION <ul><li>Write the word and balanced chemical equations for the following: </li></ul><ul><li>The reaction of zinc with aqueous hydrochloric acid produces a solution of zinc chloride and hydrogen gas. </li></ul><ul><li>Zinc + hydrochloric acid  zinc chloride + hydrogen </li></ul><ul><li>Zn(s) + 2HCl(aq)  ZnCl 2 (aq) + H 2 (g) </li></ul>
  37. 37. Try this… <ul><li>Balance the chemical equation </li></ul><ul><li>Fe(s) + H 2 O(g) Fe 3 O 4 (s) + H 2 (g) </li></ul>
  38. 38. Try this… SOLUTION <ul><li>Balance the chemical equation </li></ul><ul><li>3 Fe(s) + 4 H 2 O(g) Fe 3 O 4 (s) + 4 H 2 (g) </li></ul>
  39. 39. Translate the following chemical equation into a sentence: <ul><li>BaCl 2 (aq) + Na 2 CrO 4 (aq)  BaCrO 4 (s) + 2NaCl(aq) </li></ul>
  40. 40. Translate the following chemical equation into a sentence: SOLUTION <ul><li>BaCl 2 (aq) + Na 2 CrO 4 (aq)  BaCrO 4 (s) + 2NaCl(aq) </li></ul><ul><li>Aqueous solutions of barium chloride and sodium chromate react to produce a precipitate of barium chromate plus sodium chloride in aqueous solution </li></ul>
  41. 41. Section 2: Types of Chemical Reactions <ul><li>Synthesis </li></ul><ul><li>Decomposition </li></ul><ul><li>Single-displacement </li></ul><ul><li>Double-displacement </li></ul><ul><li>Combustion </li></ul>
  42. 42. SYNTHESIS <ul><li>AKA a Composition RXN </li></ul><ul><li>2 or more substances combine to form a new compound </li></ul><ul><li>A + X  AX </li></ul><ul><ul><li>Examples: oxygen to produce oxides of an element </li></ul></ul><ul><ul><li>2Mg(s) + O 2 (g)  2MgO(s) </li></ul></ul>
  43. 43. DECOMPOSITION <ul><li>A single compound undergoes a reaction that produces 2 or more simpler substances </li></ul><ul><li>AX  A + X </li></ul><ul><li>Electrolysis- decomposition of a substance by an electric current </li></ul>
  44. 44. DECOMPOSITION of… <ul><li>Binary Compounds </li></ul><ul><ul><li>Products: its elements </li></ul></ul><ul><li>Metal Carbonates </li></ul><ul><ul><li>Products: metal oxide and carbon dioxide gas </li></ul></ul><ul><li>Metal Hydroxides </li></ul><ul><ul><li>Products: metal oxide and water </li></ul></ul><ul><li>Metal Chlorates </li></ul><ul><ul><li>Products: metal chloride and water </li></ul></ul><ul><li>Acids </li></ul><ul><ul><li>Products: Nonmetal oxides and water </li></ul></ul>
  45. 45. EXAMPLES DECOMPOSITION of… <ul><li>Binary Compounds </li></ul><ul><ul><li>2H 2 O (l) 2H 2 (g) + O 2 (g) </li></ul></ul><ul><li>Metal Carbonates </li></ul><ul><ul><li>CaCO 3 (s) CaO(s) + CO 2 (g) </li></ul></ul><ul><li>Metal Hydroxides </li></ul><ul><ul><li>Ca(OH) 2 (s) CaO(s) + H 2 O(g) </li></ul></ul><ul><li>Metal Chlorates </li></ul><ul><ul><li>2KClO 3 (s) 2KCl(s) + 3O 2 (g) </li></ul></ul><ul><li>Acids </li></ul><ul><ul><li>H 2 CO 3 (aq) CO 2 (g) + H 2 O(l) </li></ul></ul>
  46. 46. SINGLE-DISPLACEMENT RXN <ul><li>AKA replacement reaction </li></ul><ul><li>One element replaces a similar element in a compound </li></ul><ul><li>A + BX  AX + B </li></ul><ul><li>Y + BX  BY + X </li></ul>
  47. 47. SINGLE-DISPLACEMENT RXN <ul><li>Use your textbook (page 281) and give the products of each type of single displacement reaction and an example. </li></ul><ul><li>The structure should be similar to how I did decomposition rxns </li></ul>
  48. 48. DOUBLE-DISPLACEMENT <ul><li>The ions of 2 compounds exchange places in an aqueous solution to form 2 new compounds </li></ul><ul><li>AX + BY  AY + BX </li></ul>
  49. 49. DOUBLE-DISPLACEMENT <ul><li>Use your textbook (page 282-282) and give the products of each type of double-displacement reaction and an example. </li></ul><ul><li>The structure should be similar to how I did decomposition rxns (and how you did single-displacement rxns) </li></ul>
  50. 50. COMBUSTION <ul><li>A substance combines with oxygen , releasing a large amount of energy in the form of light and heat </li></ul><ul><li>2H 2 (g) + O 2 (g)  2H 2 O(g) </li></ul>
  51. 51. Section 3: ACTIVITY SERIES OF THE ELEMENTS <ul><li>Activity: ability for an element to react </li></ul><ul><li>Activity Series: a list of elements organized according to the ease with which the elements undergo certain chemical reactions </li></ul>
  52. 52. ACTIVITY SERIES <ul><li>Help you predict whether or not a given reaction will occur and what the products will be </li></ul>
  53. 53. Think back for a minute… <ul><li>From previous knowledge, which groups can you expect to be the most and least reactive? </li></ul>I expect everyone to know the answer!
  54. 54. Activity Series <ul><li>Metals: greater activity  greater loss of electrons (form positive ions) </li></ul><ul><li>Nonmetals: greater activity  greater ease of gain of electrons (form negative ions) </li></ul>
  55. 55. Activity Series <ul><li>The order is determined by single-displacement reactions </li></ul><ul><li>The most-active element is at the top of the series and can replace any element below through a single-displacement reaction </li></ul>
  56. 56. Activity Series <ul><li>Metals: greater activity  greater loss of electrons (form positive ions) </li></ul><ul><li>Nonmetals: greater activity  greater ease of gain of electrons (form negative ions) </li></ul>
  57. 57. Activity Series <ul><li>Based on experimentation </li></ul><ul><li>Information is used as a general guide for predicting reaction outcomes </li></ul>
  58. 58. Activity Series <ul><li>Draw table 3 (page 286) in your notes </li></ul>
  59. 59. Activity Series Example <ul><li>Zn(s) + H 2 O(l)  </li></ul><ul><li>Sn(s) + O 2 (g)  </li></ul>
  60. 60. Activity Series Example <ul><li>Cd(s) + Pb(NO 3 ) 2 (aq)  </li></ul><ul><li>Cu(s) + HCl(aq)  </li></ul>
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