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Chapter 8

Chapter 8. Types of Reactions. I. Introduction. There are 5 basic reaction types: 1) Combination 2) Decomposition 3) Single Replacement 4) Double Replacement 5) Combustion. B. Three different presentations of equations are possible: 1) Molecular equation 2) ionic equation

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Chapter 8

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  1. Chapter 8 Types of Reactions

  2. I. Introduction • There are 5 basic reaction types: 1) Combination 2) Decomposition 3) Single Replacement 4) Double Replacement 5) Combustion

  3. B. Three different presentations of equations are possible: 1) Molecular equation 2) ionic equation 3) net ionic equation* * Net ionic equations are only relevant for single and double replacements

  4. C. A “net ionic equation” eliminates those equation members who are identical on the reactant side and product side 1) these are called “spectator ions” 2) If no ions are present, then all members are kept in the final equation

  5. Ex: 2 KClO3 ---> 2 KCl + 3 O2 (all members are kept in final equation) [Only molecular equation is written] Ex: Zn + 2 HCl(aq) --> ZnCl2(aq) + H2 Zn + 2 H+ + 2 Cl- --> Zn+2 + 2 Cl- + H2 Zn + 2 H+ --> Zn+2 + H2 [ the “2 Cl-” were eliminated because they did not change from reactants to products]

  6. Ex: HCl(aq) + NaOH (aq) --> NaCl (aq) + H2O (aq) H+ + Cl- + Na+ + OH- --> Na+ + Cl- + H2O H+ + OH- --> H2O [ the Cl- and Na+ were eliminated as they did not change ]

  7. II. Combination Reactions • ONLY ONE PRODUCT is formed • Possible reactants can be: 1) element + element ex: 2 H2 + O2 --> H2O ex: 2 Na + Cl2 --> 2 NaCl 2) nonmetal oxides + water --> acids ex: SO3 + H2O --> H2SO4 3) metal oxides + water --> bases ex: MgO + H2O --> Mg(OH)2

  8. III. Decomposition Reactions • ONLY ONE REACTANT • Types of reactants include: 1) chlorates --> oxygen + metal chloride ex: 2 KClO3 --> 3 O2 + 2 KCl 2) carbonate --> carbon dioxide + metal oxide ex: CaCO3 --> CO2 + CaO ex: 2 NaHCO3 --> CO2 + Na2CO3 + H2O

  9. 3) hydroxides --> water + metal oxide ex: Mg(OH)2 --> H2O + MgO 4) Hydrogen peroxide --> oxygen + water ex: 2 H2O2 --> O2 + 2 H2O 5) Binary metal oxides --> oxygen + metal ex: 2 HgO --> O2 + 2 Hg

  10. IV. Single Replacement Reactions • Element + compound --> element + compound • Types of single replacement: 1) metal + acid --> hydrogen + salt ex: Zn + HCl(aq) --> H2 + ZnCl2 (aq) Note: these metals do not produce H2: Cu Ag Hg Pt Au

  11. 2) Metal + salt --> metal + salt ex: Cu + 2 AgNO3(aq) --> 2 Ag + Cu(NO3)2 (aq) 3) Metal + water --> hydrogen + base ex: 2 Na + 2 H2O --> H2 + 2 NaOH(aq) Note: DO NOT produce H2 + Na2O; Think of it as: ex: 2 Na + 2 HOH --> H2 + 2 NaOH(aq) 4) Non metal + salt --> non metal + salt F2 + 2 NaCl --> Cl2 + 2 NaF

  12. IV. Double Replacement Reactions • Involves 2 compounds reacting --> 2 new compounds formed • Subscripts depend on partner ions • Solubility rules MUST be used to predict precipitated products • Products include precipitates, water, or gases

  13. E. Examples with various products: 1) precipitated products (using solubility rules) ex: 2 NaI + Pb(NO3)2 --> 2 NaNO3 + PbI2 AgNO3 + NaCl --> NaNO3 + AgCl 2) water is formed (neutralization reactions) ex: HCl + NaOH --> NaCl + H2O acid + base --> salt + water

  14. 3) Gases are formed… these products break down into these gases: a) NH4OH --> NH3 + H2O b) H2CO3 --> CO2 + H2O c) H2SO3 --> SO2 + H2O Ex: NH4Cl + NaOH --> NaCl + NH3 + H2O Na2CO3 + 2 HCl --> 2 NaCl + CO2 + H2O Na2SO3 + HCl --> NaCl + SO2 + H2O

  15. V. Combustion Reactions • Use oxygen as a reactant • Every element bonds with an oxygen Ex: CH4 + 2 O2 --> CO2 + 2 H2O [All “CxHy” compounds produce CO2 + H2O] Ex: CS2 + 2 O2 --> CO2 + 2 SO2

  16. VI. Advanced Equation Writing A. All equations will be given in a sentence without any chemical symbols ex: Magnesium ribbon is burned in air you write: Mg + O2 --> B. Solids are NEVER written as ions ex: “Solid sodium carbonate is added to…” Na2CO3 + ….

  17. C. Strong acids ALWAYS ionize Weak acids NEVER ionize The 7 Strong acids: HCl HBr HI HNO3 HClO3 HClO4 H2SO4 D. Solutions always ionize…(but not weak acids) E. Soluble products always ionize F. Phases are not required (ex: aq, s, l, g)

  18. Examples: • Aluminum metal is added to a solution of hydrochloric acid Procedure: 2 Al + 6 HCl --> 2 AlCl3 + 3 H2 2 Al + 6 H+ + 6 Cl- --> 2 Al+3 + 6 Cl- + 3 H2 FINAL ANS: 2 Al + 6 H+ --> 2 Al+3 + 3 H2

  19. Examples: 2) Sodium oxide powder is added to water Procedure: Na2O + H2O --> 2 NaOH Na2O + H2O --> 2 Na+ + 2 OH- FINAL ANS: Na2O + H2O --> 2 Na+ + 2 OH-

  20. Examples: 3) Solutions of barium acetate and sodium sulfate are mixed Procedure: Ba(C2H3O2)2 + Na2SO4 --> BaSO4 + 2 NaC2H3O2 Ba+2 + 2 C2H3O2- + 2 Na+ + SO4-2 --> BaSO4 + 2 Na+ + 2 C2H3O2- FINAL ANS: Ba+2 + SO4-2 --> BaSO4

  21. Examples: 3) Solid sodium hydroxide is added to a solution of acetic acid Procedure: NaOH + HC2H3O2 --> NaC2H3O2 + H2O NaOH + HC2H3O2 --> Na+ + C2H3O2- + H2O FINAL ANS: NaOH + HC2H3O2 --> Na+ + C2H3O2- + H2O

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