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CHAPTER 8

CHAPTER 8. Chemical Equations & Reactions. Chemical Equations. Represented w/ symbols & formulas Identifies reactants & products Identifies amounts of each. What Do They Tell Us?. Visual Concepts. Chapter 8. Signs of a Chemical Reaction. Visual Concepts. Chapter 8. Precipitate.

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CHAPTER 8

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  1. CHAPTER 8 Chemical Equations & Reactions

  2. Chemical Equations • Represented w/ symbols & formulas • Identifies reactants & products • Identifies amounts of each

  3. What Do They Tell Us?

  4. Visual Concepts Chapter 8 Signs of a Chemical Reaction

  5. Visual Concepts Chapter 8 Precipitate

  6. Section1 Describing Chemical Reactions Chapter 8 Evidence of a Chemical Reaction • solution color changes • solution bubbles • copper is used up

  7. Evidence of a Chemical Reaction • Produces heat and/or light • Produces gas • Forms a precipitate (a solid appears) • Color change • Temperature change

  8. Balancing Chemical Reactions • Why do it? • We need to know exactly how much of everything there is. (Ch. 9 Stuff) • What do you do? • Count • Make sure the exact same number of atoms exists on both sides of the eqn.

  9. Visual Concepts Chapter 8 Reading a Chemical Equation

  10. Balancing a Chemical Equation by Inspection

  11. Rules of Balancing • Write each individual formula (Criss-Cross Applesauce) • Take inventory • Use coefficients to balance. • Check your work.

  12. Coefficients • #’s that go in front • They multiply • Example H2O two hydrogens / 1 oxygen 2 H2O 4 hydrogens/ 2 oxygens 5 H2O 10 hydrogens / 5 oxygens

  13. Sample Problem A Na + Cl2 NaCl 1

  14. Sample Problem A Na + Cl2 NaCl 1 2

  15. Sample Problem A Na + Cl2 NaCl 1 2 1

  16. Sample Problem A Na + Cl2 NaCl 1 2 1 1 Cl are not equal. Use a coefficient!

  17. Sample Problem A Na + Cl2 2 NaCl Now count again!

  18. Sample Problem A Na + Cl2 2 NaCl 1

  19. Sample Problem A Na + Cl2 2 NaCl 1 2

  20. Sample Problem A Na + Cl2 2 NaCl 1 2 2

  21. Sample Problem A Na + Cl2 2 NaCl 1 2 2 2 Now the Na atoms aren’t equal! Use another coefficient.

  22. Sample Problem A 2 Na + Cl2 2 NaCl

  23. Sample Problem A 2 Na + Cl2 2 NaCl 2

  24. Sample Problem A 2 Na + Cl2 2 NaCl 2 2

  25. Sample Problem A 2 Na + Cl2 2 NaCl 2 2 2 2 Now everything is EQUAL! 2 Na + Cl2 2 NaCl

  26. Sample Problem B Ca3(PO4)2 + Mg(OH)2 → Ca(OH)2+ Mg3(PO4)2 COUNT! Ca 3 P 2 Mg 1 H 2 O 8 + 2 = 10 Ca 1 P 2 Mg 3 H 2 O 2 + 8 = 10

  27. Sample Problem B Ca3(PO4)2 + Mg(OH)2 → 3 Ca(OH)2+ Mg3(PO4)2 Ca 3 P 2 Mg 3 H 6 O 6 + 8 = 14 Ca 3 P 2 Mg 1 H 2 O 8 + 2 = 10

  28. Sample Problem B Ca3(PO4)2 + 3 Mg(OH)2 → 3Ca(OH)2+ Mg3(PO4)2 Ca 3 P 2 Mg 3 H 6 O 8 + 6 = 14 Ca 3 P 2 Mg 3 H 6 O 6 + 8 = 14

  29. Special Rules • If it’s a metal by itself, just write the symbol. Copper Cu • If it’s a nonmetal by itself, write the symbol with a subscript 2. Nitrogen N2 • Leave Oxygen for last!

  30. Paint Can Demo • What did I do?

  31. Paint Can Demo

  32. Types of Chemical Reactions

  33. Visual Concepts Chapter 8 Synthesis Reactions

  34. Synthesis Reactions • Smaller compounds make one bigger one • A + B  AB • Example: Na + Cl  NaCl

  35. Visual Concepts Chapter 8 Decomposition Reaction

  36. Decomposition • Larger compounds break down to smaller ones • Opposite of synthesis reaction • AB  A + B • Example: 2 KClO3 2 KCl + 3 O2

  37. Visual Concepts Chapter 8 Single Displacement Reaction

  38. Single Replacement Reaction • One atom changes places with another atom • A + BC  AC + B • Example: Zn + 2 HCl  H2 + ZnCl2

  39. Visual Concepts Chapter 8 Double-Displacement Reaction

  40. Double Replacement Reaction • Two atoms trade places • AB + CD  AD + CB • Example: 2 KI + Pb(NO3)2 2 KNO3 + PbI2

  41. Visual Concepts Chapter 8 Precipitation Reaction

  42. Visual Concepts Chapter 8 Combustion Reaction

  43. Combustion Reaction • Anything reacting with O2 • X + O2 CO2 + H2O

  44. 1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds? A. synthesis reaction B. decomposition reaction C. single-displacement reaction D. double-displacement reaction

  45. 1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds? A. synthesis reaction B. decomposition reaction C. single-displacement reaction D. double-displacement reaction

  46. 2. Which of these sentences correctly states the law of conservation of mass? F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants. G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants. H. In a chemical reaction, the mass of the products is always less than the mass of the reactants. I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

  47. 2. Which of these sentences correctly states the law of conservation of mass? F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants. G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants. H. In a chemical reaction, the mass of the products is always less than the mass of the reactants. I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

  48. 3. Of these reaction types, which has only one reactant? A. decomposition B. displacement C. oxidation D. synthesis

  49. 3. Of these reaction types, which has only one reactant? A. decomposition B. displacement C. oxidation D. synthesis

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