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Intro to Reactions (p. 241 – 250)

Ch. 8 – Chemical Reactions. Intro to Reactions (p. 241 – 250). A.Signs of a Chemical Reaction. Evolution of ________ and ________ Formation of a _______ Formation of a ___________ _________ change. B.Law of Conservation of Mass. mass is neither created nor destroyed in a chemical reaction.

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Intro to Reactions (p. 241 – 250)

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  1. Ch. 8 – Chemical Reactions Intro to Reactions(p. 241 – 250) C. Johannesson

  2. A.Signs of a Chemical Reaction • Evolution of ________ and ________ • Formation of a _______ • Formation of a ___________ • _________ change C. Johannesson

  3. B.Law of Conservation of Mass • mass is neither created nor destroyed in a chemical reaction • total mass stays the same • atoms can only rearrange 4 H 2 O 4 H 2 O 36 g 4 g 32 g C. Johannesson

  4. C. Chemical Equations A+B  C+D REACTANTS PRODUCTS C. Johannesson

  5. C. Chemical Equations p. 246 C. Johannesson

  6. D. Writing Equations 2H2(g) + O2(g)  2H2O(g) • Identify the substances involved. • Use symbols to show: • How many? - coefficient • Of what? - chemical formula • In what state? - physical state • Remember the diatomic elements. C. Johannesson

  7. D. Writing Equations Two atoms of aluminum react with three units of aqueous copper(II) chloride to produce three atoms of copper and two units of aqueous aluminum chloride. • How many? • Of what? • In what state?

  8. Describing Coefficients: individual atom = “atom” covalent substance = “molecule” ionic substance = “unit” E. Describing Equations 3CO2 2Mg  4MgO  3 molecules of carbon dioxide 2 atoms of magnesium 4 units of magnesium oxide C. Johannesson

  9. E. Describing Equations Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g) • How many? • Of what? • In what state?

  10. Ch. 8 – Chemical Reactions II. Balancing Equations(p. 250-254) C. Johannesson

  11. A. Balancing Steps 1. _________ the unbalanced equation. 2. _________ atoms on each side. 3. _____ coefficients to make #s equal. Coefficient  subscript = # of atoms 4. _________ coefficients to lowest possible ratio, if necessary. 5. Double check atom __________!!! C. Johannesson

  12. B. 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 SO4” instead of “1 S” and “4 O” C. Johannesson

  13. C. Balancing Example Al + CuCl2 Cu + AlCl3 Al Cu Cl Aluminum and copper(II) chloride react to form copper and aluminum chloride.

  14. Ch. 8 – Chemical Reactions III. Types of Chemical Reactions(p. 256 - 267) C. Johannesson

  15. A. Combustion • the burning of any substance in O2 to produce heat A + O2 B CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) C. Johannesson

  16. A. Combustion • Products: • contain oxygen • hydrocarbons form CO2 + H2O Na(s)+ O2(g)  Na2O(s) 4 2 C3H8(g)+ O2(g)  CO2(g) + H2O(g) C. Johannesson

  17. B. _____________ • the combination of 2 or more substances to form a compound • only one product A + B  AB C. Johannesson

  18. B. _____________ H2(g) + Cl2(g)  2 HCl(g) C. Johannesson

  19. B. _____________ • Products: • ionic - cancel charges • covalent - hard to tell Al(s)+ Cl2(g)  AlCl3(s) C. Johannesson

  20. C. _______________ • a compound breaks down into 2 or more simpler substances • only one reactant AB  A + B C. Johannesson

  21. C. ________________ 2 H2O(l)  2 H2(g) + O2(g) C. Johannesson

  22. C. ________________ • Products: • binary - break into elements • others - hard to tell KBr(l)  K(s) + Br2(l) C. Johannesson

  23. The “Activity Series” of Metals • Lithium • Potassium • Calcium • Sodium • Magnesium • Aluminum • Zinc • Chromium • Iron • Nickel • Lead • Hydrogen • Bismuth • Copper • Mercury • Silver • Platinum • Gold • Metals can replace other metals, provided they are above the metal they are trying to replace (for example, zinc will replace lead) Higher activity • Metals above hydrogen can replace hydrogen in acids. • Metals from sodium upward can replace hydrogen in water. Lower activity

  24. The “Activity Series” of Halogens Higher Activity Halogens can replace other halogens in compounds, provided they are above the halogen they are trying to replace. Fluorine Chlorine Bromine Iodine Lower Activity 2NaF(s) + Cl2(g) 2NaCl(s) + F2(g) ??? MgCl2(s) + Br2(g) No Reaction! ???

  25. D. __________ ________________ • one element replaces another in a compound • metal replaces metal (+) • nonmetal replaces nonmetal (-) A + BC  B + AC C. Johannesson

  26. D. __________ ________________ Cu(s) + 2AgNO3(aq)  Cu(NO3)2(aq) + 2Ag(s) C. Johannesson

  27. D. __________ ________________ • Products: • metal  metal (+) • nonmetal  nonmetal (-) • free element must be more active(check activity series) Fe(s)+ CuSO4(aq)  Cu(s)+ FeSO4(aq) Br2(l)+ NaCl(aq)  N.R. C. Johannesson

  28. E. __________ ________________ • ions in two compounds “change partners” • cation of one compound combines with anion of the other AB + CD  AD + CB C. Johannesson

  29. E. __________ ________________ Pb(NO3)2(aq) + K2CrO4(aq)  PbCrO4(s) + 2KNO3(aq) C. Johannesson

  30. E. __________ ________________ • Products: • switch negative ions • one product must be insoluble(check solubility table) Pb(NO3)2(aq)+ KI(aq)  2 2 PbI2(s)+ KNO3(aq) NaNO3(aq)+ KI(aq)  N.R. C. Johannesson

  31. Ch. 17 – Chemical Reactions IV. Reaction Energy(p. 514 - 517) C. Johannesson

  32. A. Reaction Pathway • Shows the change in energy during a chemical reaction C. Johannesson

  33. B. _____________ Reaction energyreleased • reaction thatreleases energy • products have lower PE than reactants 2H2(l) + O2(l)  2H2O(g) + energy C. Johannesson

  34. C. _____________ Reaction energyabsorbed • reaction that absorbs energy • reactants have lower PE than products 2Al2O3+ energy 4Al + 3O2 C. Johannesson

  35. Ch. 17 – Chemical Reactions V. Reaction Rate(p. 532 - 541) C. Johannesson

  36. A. Collision Theory • Reaction rate depends on the collisions between reacting particles. • Successful collisions occur if the particles... • collide with each other • have the correct orientation • have enough kinetic energy to break bonds C. Johannesson

  37. A. Collision Theory • Particle Orientation Required Orientation Unsuccessful Collisions Successful Collision C. Johannesson

  38. A. Collision Theory Activation Energy • _____________ Energy (Ea) • minimum energy required for a reaction to occur C. Johannesson

  39. A. Collision Theory Ea • Activation Energy • depends on reactants • low Ea = fast rxn rate C. Johannesson

  40. B. Factors Affecting Rxn Rate • ______________ __________ • high SA = fast rxn rate • more opportunities for collisions • Increase surface area by… • 1. • 2. C. Johannesson

  41. B. Factors Affecting Rxn Rate • _______________ • high conc = fast rxn rate • more opportunities for collisions C. Johannesson

  42. B. Factors Affecting Rxn Rate • _______________ • high temp = fast rxn rate • high KE • fast-moving particles • more likely to reach activation energy C. Johannesson

  43. B. Factors Affecting Rxn Rate • Temperature Analogy: 2-car collision 5 mph “fender bender” C. Johannesson 50 mph “high-speed crash”

  44. B. Factors Affecting Rxn Rate • _______________ • substance that increases rxn rate without being consumed in the rxn • lowers the activation energy C. Johannesson

  45. B. Factors Affecting Rxn Rate • Enzyme Catalysis C. Johannesson

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