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Chemical Reactions

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  1. Chemical Reactions Chemistry Matter and Change Chapter 9

  2. Chapter 9 Big Idea Millions of chemical reactions in and around you transform reactants into products, resulting in the absorption or release of energy.

  3. Reactions and Equations Chemistry Matter and Change Chapter 9.1

  4. 9.1 Main Idea Chemical reactions are represented by balanced chemical equations.

  5. 9.1 Objectives Recognize evidence of chemical reactions Represent chemical reactions with equations Balance chemical equations

  6. 9.1 Review Vocabulary and Concepts • Chemical change • Dalton’s atomic theory • Law of conservation of mass

  7. 9.1 New Vocabulary and Concepts • Chemical reaction • Reactant • Product • Chemical equation • Coefficient • (s), (l), (g), (aq) •  • 

  8. Chemical reaction • Process by which atoms are rearranged

  9. Evidence of chemical reactions • Temperature/energy change • Gas emitted (odor) • Precipitate forms • Color change • Change of substance(s)

  10. Representing chemical reactions • 4+1=2+3 • Reactant + reactant  product + product • Need one or more reactants and one or more products

  11. Symbols you need to know

  12. Three types of equations • Word equations • Skeletal equations • Chemical equations

  13. Types of equations Skeletal Chemical Word • Indicates identity (by molecular formulae) of substances involved • Indicates identity (by molecular formulae) and relative quantity of substances involved • Indicates identity of substances involved Hydrogen + oxygen  water H2 + O2 H2O 2H2 + O2 2H2O

  14. Balancing chemical equations • Conservation of mass • What goes in, must come out • What comes out, must have gone in

  15. Balancing equations: • Write out word equation • Write out skeletal equation • Balance each atom • MINOH (aka Tarzan method) • Metals, ions, nonmetals, oxygen, hydrogen • Start with “rare” elements • Leave atoms in multiple places until last “Me know chemistry,” said Tarzan as he climbed the stoichiom-eh-tree.

  16. Sample 1 • Magnesium and bromine form magnesium bromide • Mg + Br2 MgBr2 (balanced) • Magnesium and oxygen form magnesium oxide • Mg + O2  MgO (not balanced) • 2Mg + O2  2MgO (balanced)

  17. Sample 2 • Nitrogen and hydrogen form ammonia • N2 + H2 NH3 • N2 + 3H2  2NH3

  18. Sample 3 • Zn + HCl  ZnCl2+ H2 • Na + H2O NaOH + H2

  19. For you to practice • Fe + O2 Fe2O3 • Fe2O3 + H2Fe + H2O • Sb+ O2 Sb4O6 • Al + HClAlCl3 + H2 • H2O + CO2 C6H12O6 + O2

  20. More hints • Keep polyatomic ions together if they appear on both sides of the equation • Diatomics always exist in pairs

  21. Can you… • Recognize evidence of chemical reactions • Represent chemical reactions with equations • Balance chemical equations

  22. Classifying Chemical Reactions Chapter 9.2

  23. 9.2 Main Idea There are five types of chemical reactions: synthesis, decomposition, single replacement, double replacement, and combustion

  24. 9.2 Objectives • Classify chemical reactions • Identify the characteristics of different classes of chemical reactions

  25. 9.2 Review Vocabulary and Concepts • Metal • Nonmetal • precipitate

  26. 9.2 New Vocabulary and Concepts • Synthesis reaction • Combustion reaction • Decomposition reaction • Single-replacement reaction • Double replacement reaction

  27. 5 Types of chemical reactions • Synthesis • Decomposition • Combustion • Single replacement (displacement) • Double replacement (displacement)

  28. Synthesis • E+EC • Two or more reactants form one product • 2H2 + O2  2H2O + 

  29. Decomposition • CE+E • One reactant breaks down into two or more products • 2Fe2O3  4Fe + 3O2 + 

  30. Single replacement • C + E  E + C • One element in a compound is replaced by another element • Br2 + MgCl2  MgBr2 + Cl2 + + 

  31. Double replacement • C+CC+C • Elements in both compounds change partners • Ca(OH)2+2HClCaCl2+2H2O + + 

  32. Combustion • C + O2 CO2 + H2O • A compound plus oxygen produces an oxide and water • 2C2H6 + 7O2  4CO2 + 6H20

  33. Summary of reaction types

  34. Predict the product(s) • NaOH+HCl  • CH4+O2  • LiCl+Br2  • Fe+O2  • H2O 

  35. Can you… • Classify chemical reactions • Identify the characteristics of different classes of chemical reactions

  36. Reactions in Aqueous Solutions 9.3

  37. 9.3 Main Idea Double replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.

  38. 9.3 Objectives • Describe aqueous solutions • Write complete ionic and net ionic equations for chemical reactions in aqueous solutions • Predict whether reactions in aqueous solutions will produce a precipitate, water or a gas

  39. 9.3 Review Vocabulary and Concepts • Solution • Ionic formulae • Precipitate • Ion

  40. 9.3 New Vocabulary and Concepts • Aqueous solution • Solute • Solvent • Complete ionic equation • Spectator ion • Net ionic equation

  41. Aqueous solutions • Solvent- water • Solute- other substance(s) • HCl(aq) is hydrochloric acid in water

  42. Types of reactions in aqueous solutions • Form Gas • Usually Double displacement

  43. Types of reactions in aqueous solutions • Form Precipitate • Usually double replacement • 2KI + Pb(NO3)2  2KNO3+PbI2 Lead iodide

  44. Types of reactions in aqueous solutions • Form Water • Acid/base reactions • Double displacement • Also form a salt HCl + NaOH NaCl+ HOH

  45. Net Ionic Reactions • Allow you to predict the products in a double replacement reaction • HBr(aq)+NaOH(aq)H2O(l)+NaBr(aq) • H+(aq) + Br-(aq) + Na+ (aq) + OH-(aq) H2O(l) + Na+(aq)+ Br-(aq) • H++OH-H2O

  46. Writing Net Ionic Reactions • Perchloric acid reacts with aqueous potassium carbonate forming potassium chlorate, carbon dioxide gas and water. Step 1: figure out the chemical formulae and phase for all substances • Perchloric acid: HClO4(aq) • Potassium carbonate: K2CO3(aq) • Water: H2O(l) • Carbon dioxide: CO2(g) • Potassium perchlorate: KClO4

  47. Writing Net Ionic Reactions • Perchloric acid reacts with aqueous potassium carbonate forming potassium chlorate, carbon dioxide gas and water. Step 2: write the skeletal equation HClO4(aq)+K2CO3(aq)  H2O(l)+CO2(g)+KClO4(aq)

  48. Writing Net Ionic Reactions • Perchloric acid reacts with aqueous potassium carbonate forming potassium chlorate, carbon dioxide gas and water. Step 3: balance the equation 2HClO4(aq) + K2CO3(aq)  H2O(l) +CO2(g) + 2KClO4(aq)

  49. Writing Net Ionic Reactions • Perchloric acid reacts with aqueous potassium carbonate forming carbon dioxide gas and water. Step 4: Write the complete ionic equation 2H+(aq) + 2ClO4-(aq) + 2K+(aq) +CO32-(aq)  H2O(l) + CO2(g) + 2K+(aq) + 2ClO4-(aq)

  50. Writing Net Ionic Reactions • Perchloric acid reacts with aqueous potassium carbonate forming carbon dioxide gas and water. Step 5: Cross out balanced terms 2H+(aq) + 2ClO4-(aq) + 2K+(aq) +CO32-(aq)  H2O(l) + CO2(g) + 2K+(aq) + 2ClO4-(aq)