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Chemical Equations & Reactions

Chemical Equations & Reactions. 4 Al( s ) + 3 O 2 ( g ) 2 Al 2 O 3 ( s ). Chemical Equations. 4 g Al + 3 g O 2 yield 2 g Al 2 O 3. This equation means:. 4 Al atoms + 3 O 2 molecules yield 2 molecules of Al 2 O 3. or.

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Chemical Equations & Reactions

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  1. Chemical Equations & Reactions

  2. 4 Al(s) + 3 O2(g) 2 Al2O3(s) Chemical Equations 4 g Al + 3 g O2 yield 2 g Al2O3 This equation means: 4 Al atoms + 3 O2 molecules yield 2 molecules of Al2O3 or 4 Al moles + 3 O2moles yield 2 moles of Al2O3 2 mol Al2O3@102g/mol 4 mol Al@27g/mol 3 mol O2@32g/mol 108 g + 96 g = 204 g

  3. Visualizing a Chemical Reaction 2 2 Na + Cl2 NaCl 10 5 10 10 ? 10 5 ___ mole Na ___ mole Cl2 ___ mole NaCl

  4. Types of Chemical Reactions Synthesis (combination) reaction A + B  AB Decomposition reaction AB  A + B ASingle-replacement reaction A + BC  AC + B element compound compound element BDouble-replacement reaction AB + CD  AD + CB All compounds… CxHy + O2 CO2 + H2O Combustion reaction (of a hydrocarbon) Ause activity series to predict products/reactivity Buse solubility chart to predict products/reactivity

  5. Practice: Balance and Classify • Ca(OH)2+ HCl CaCl2 + H2O ________________________ • C2H4 + O2 CO2 + H2O ________________________ • N2 + O2 N2O ________________________ • SrCO3 SrO + CO2 ________________________ • NaI + Br2NaBr + I2 ________________________ • C2H4O + O2 CO2 + H2O ________________________ • MgBr2+ (NH4)2SO3 MgSO3+ NH4Br ________________________ • AgClO3+ (NH4)2Cr2O7 Ag2Cr2O7+ NH4ClO3______________________ • Cs + H2O CsOH + H2 ________________________ • Fe + O2 Fe3O4 ________________________

  6. Additional Symbols Used in Chemical Equations “Yields”; indicates result of reaction Used to indicate a reversible reaction (equilibrium) A reactant or product in the solid state; also used to indicate a precipitate Alternative to (s), but used only to indicate a precipitate A reactant or product in the liquid state A reactant or product in an aqueous solution (dissolved in water) A reactant or product in the gaseous state (s) (l) (aq) (g)

  7. Additional Symbols Used in Chemical Equations Alternative to (g), but used only to indicate a gaseous product Reactants are heated Pressure at which reaction is carried out, in this case 2 atm Pressure at which reaction is carried out exceeds normal atmospheric pressure Temperature at which reaction is carried out, in this case 0 oC Formula of catalyst, in this case manganese (IV) oxide, used to alter the rate of the reaction D 2 atm pressure 0 oC MnO2

  8. Signs of Chemical Reactions There are five main signs that indicate a chemical reaction has taken place: release input change in color change in odor production of new gases or vapor input or release of energy difficult to reverse

  9. Combustion O2 + + C4H10 4 13/2 5 CO2 H2O 2 8 10 13 + General form: CxHx + O2 CO2 H2O carbon dioxide carbon-hydrogen compound water oxygen

  10. Writing Equations Practice Write a balanced equation for the reaction between chlorine and solid sodium bromide to produce bromine and solid sodium chloride. 1. Write a word equation for the reaction chlorine + sodium bromide  bromine + sodium chloride 2. Write the correct formulas for all reactants and products, (with correct phases of matter) 3. Balance the resulting equation 2 2 Cl2(g) + NaBr(s)  Br2(l) + NaCl(s)

  11. Write the balanced equation for the aqueous reaction between aluminum sulfate and calcium chloride to form a white precipitate of calcium sulfate. 1) Write a word equation for the reaction ? ? aluminum sulfate + calcium chloride  calcium sulfate + aluminum chloride 2) Write the correct formulas for all reactants and products 3) Balance the resulting equation 2 3 3 Al2(SO4)3(aq) + CaCl2(aq)  CaSO4(s) + AlCl3 (aq)

  12. Ca Printable Version of Activity Series Activity Series Element Reactivity Li Rb K Ba Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H2 Cu Hg Ag Pt Au Foiled again: Aluminum is knocked out by Calcium Halogen Reactivity F2 Cl2 Br2 I2

  13. Predict if these reactions will occur… Al + MgCl2 3 2 2 3 Mg + AlCl3 Can magnesium replace aluminum? • Activity Series YES, magnesium is more reactive than aluminum. NR (No Reaction) Al + MgCl2 Can aluminum replace magnesium? Therefore, no reaction will occur. NO, aluminum is less reactive than magnesium. Order of reactants DOES NOT determine how they react. No reaction MgCl2 + Al We must determine if the lone element is more reactive than the bonded one… metals replace metals or non-metals replace nonmetals

  14. A + BC AC + B More SR Reactions… Activity Series Li Rb K Ba Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H2 Cu Hg Ag Pt Au “Magic blue-earth” FeCl2 + Cu Fe + CuCl2 Yes Can Fe replace Cu? Zinc in nitric acid F2 Cl2 Br2 I2 2 Zn + HNO3 Zn(NO3)2 + H2 Yes Can Zn replace H? NO REACTION MgBr2 + Cl2 MgCl2 + Br2 No Can Br replace Cl? General Form

  15. Double Replacement Reactions K2CO3 (aq) Potassium carbonate + BaCl2 (aq) Barium chloride 2 KCl (aq) Potassium chloride + BaCO3 (s) Barium carbonate

  16. Formation of a solid precipitate: AgNO3(aq) + KCl(aq)  KNO3 (aq) + AgCl(s)

  17. chromate hydroxide carbonate bromide chloride sulfide sulfate nitrate phosphate iodide acetate Legend SOLID SOLID AQUEOUS i = insoluble ss = slightly soluble s = soluble d = decomposes n = not isolated

  18. Solubility Rules 1. Most nitrates are soluble. • Most salts containing Group I ion and ammonium ion, NH4+, are soluble. • Most chloride, bromide, and iodide salts are soluble, except Ag+, Pb2+ and Hg22+. 4. Most sulfate salts are soluble, except BaSO4, PbSO4, Hg2SO4, and CaSO4. • Most hydroxides except Group 1 and Ba(OH)2, Sr(OH)2, and Ca(OH)2 are only slightly soluble. • Most sulfides, carbonates, chromates, and phosphates are only slightly soluble. Ohn-Sabatello, Morlan, Knoespel, Fast Track to a 5 Preparing for the AP Chemistry Examination2006, page 91

  19. Na2CO3 FeCO3 FeCl2 NaCl + + (aq) (s) Predict if a reaction will occur when you combine aqueous solutions of iron (II) chloride and sodium carbonate… If the reaction does occur, write a balanced chemical equation showing it (be sure to include phase notation). Balanced chemical equation iron (II) carbonate iron (II) chloride + sodium carbonate + sodium chloride CO32- CO32- Na+ Fe2+ Fe2+ Cl - Cl- Na+ CO3 FeCO3 Na2 Cl2 Fe NaCl (aq) (s) Using the SOLUBILITY TABLE: sodium chloride is soluble iron (II) carbonate is insoluble 2 (aq) (aq)

  20. Predict if a reaction will occur when you combine aqueous solutions of potassium chloride and sodium nitrate… If the reaction does occur, write a balanced chemical equation showing it (be sure to include phase notation). NR potassium nitrate potassium chloride + sodium nitrate + sodium chloride NO3- NO3- Na+ K+ K+ Cl - Na+ Cl- NaNO3 (aq) KNO3 KCl(aq) NaCl (aq) (aq) Using the SOLUBILITY TABLE: sodium chloride is soluble potassium nitrate is soluble Notice that nothing has really changed because the ions are still dissolved in water!

  21. NO3– NO3– NO3– NO3– Pb2+ Pb2+ Na+ Na+ CI– CI– Ions in Aqueous Solution Expt. Pb(NO3)2(s) Pb(NO3)2(aq) + H2O(l) Pb2+(aq) + 2 NO3–(aq) in solution, aqueous, soluble, dissolved add water Dissociation reactions: solids mixed with water dissociate into ions NaCI(aq) NaCI(s) + H2O(l) Na+(aq) + CI–(aq) • Mix them and get… • Balance to get complete ionic equation… • Cancel spectator ions to get net ionic equation… Chem Think

  22. Pb(NO3)2(aq) + NaCI(aq) NO3– NO3– NO3– NO3– Pb2+ Pb2+ Na+ Na+ Na+ Na+ CI– CI– CI– CI– + 2 Na1+(aq) + 2 CI–(aq) Pb2+(aq) + 2 NO31–(aq) + 2 Na1+(aq) PbCI2(s) + 2 NO31–(aq) Pb2+(aq) + 2 CI–(aq) PbCI2(s) Solubility Chart Mix them and get… (aq) PbCI2 + NaNO3 (s) 2 2 Solid (precipitate) in solution (aqueous) Balance to get complete ionic equation…separate anything (aq) Cancel spectator ions to get net ionic equation…

  23. Pre-lab: • 1. What ions are present in the following solutions? • NaCl(aq) ____________________ AgNO3(aq) ____________________ • When these solutions are mixed together, a precipitate is seen. What are the new combinations of ions that could have formed the precipitate? • ____________________ and ____________________ • Using the solubility table, which new combination will form a precipitate? • ____________________  • Which new combination will remain in solution? • ____________________ • 5. Write the complete ionic equation for this reaction. Be sure to indicate the correct phase (reaction condition) for each reactant and each product. • 6. Write the net ionic equation for this reaction by canceling out spectators. Again, include the phases (reaction conditions). • 7. Explain why you would expect no reaction between solutions of KOH(aq) and NaOH(aq). Na+(aq) Cl-(aq) Ag+(aq) NO3-(aq) Ag+(aq) Na+(aq) NO3-(aq) Cl-(aq) Ag+(aq) AgCl(s) Cl-(aq) Na+(aq) NO3-(aq) Na+(aq) + Na+(aq) + NO3-(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) AgCl(s) Ag+(aq) + Cl-(aq) AgCl(s) When the cations switch places they end with a hydroxide (no new combination is formed)

  24. Zn(NO3)2(aq) + Ba(OH)2(aq) Zn(OH)2(s) + Ba(NO3)2(aq) OH– NO3– Ba2+ Zn2+ NO3– OH– + Ba2+(aq) + 2OH–(aq) Zn2+(aq) + 2 NO3–(aq) + Ba2+(aq) Zn(OH)2(s) + 2 NO3–(aq) Zn2+(aq) + 2 OH–(aq) Zn(OH)2(s) Mix together Zn(NO3)2(aq) and Ba(OH)2(aq): Solubility Chart Mix them and get… Zn(NO3)2(aq) Ba(OH)2(aq) Zn2+(aq) + 2 NO3–(aq) Ba2+(aq) + 2 OH–(aq) Balance to get completeionic equation… Cancel spectator ions to get net ionic equation…

  25. Separation of Cations You have a solution containing Fe2+, Cu2+, Ba2+, Ag+ and K+ ions. By what means could you separate these ions from each other? • In Chem I, we discussed various ways to separate things… • Distillation • Filtration • Centrifugation • Reactivity Will any of these work to separate aqueous ions?

  26. Separation of Cations Fe2+, Cu2+, Ba2+, Ag+, K+ (aq) + Cl-(aq) Fe2+, Cu2+, Ba2+, K+ (aq) AgCl(s) + SO42- (aq) Fe2+, Cu2+, K+ (aq) BaSO4(s) + CrO42- (aq) Fe2+, K+(aq) CuCrO4(s) + S2-, PO43- OH- or CO32- (aq) K+(aq) FeS, Fe3(PO4)2 , Fe(OH)2 , or FeCO3(s)

  27. Separation of Cations Try this example on your own… Pb2+, Ca2+, Zn2+, NH4+(aq) + CrO42-(aq) Ca2+, Zn2+, NH4+ (aq) PbCrO4 (s) + SO42- (aq) Zn2+, NH4+(aq) CaSO4(s) + CO32-, PO43- OH-or S2-(aq) ZnCO3,Zn3(PO4)2, Zn(OH)2, or ZnS(s) NH4+(aq)

  28. Summary of Classes of Reactions Chemical reactions Double Replacement reactions Oxidation-Reduction Reactions Acid-Base Reactions Combustion Reactions Synthesis and Decomposition reactions Single Replacement reactions

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