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Chapter 11

Chapter 11. Chemical Reactions. Do Now. Pg-3 of Notes Pkt. Label the equation using the following terms: Reactants Products And Yield Coefficient Subscript Solid Liquid Gas Aqueous. Yield or produce. And or Reacts with. Subscript. Coefficient.

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Chapter 11

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  1. Chapter 11 Chemical Reactions

  2. Do Now Pg-3 of NotesPkt Label the equation using the following terms: Reactants Products And Yield Coefficient Subscript Solid Liquid Gas Aqueous Yield or produce And or Reacts with Subscript Coefficient 3H2SO4 (aq) + 2Al (s) Al2(SO4)3 (l) + 3H2 (g) Aqueous Liquid Gas Solid Reactants Products

  3. Collision Model Key Idea: • The molecules must touch (or collide) to react with proper orientation. • Collisions must have enough energy (Ea) • Only a small fraction of collisions produces a reaction. Why? Particles lacking the necessary KE to react will bounce apart unchanged when they collide

  4. Activation Energy, Ea Activation energy:is the minimum energy needed for a reaction to occur. Collisions must have enough energyto produce the reaction: must equal or exceed Ea

  5. MnO2 H2O2(aq) H2O(l) + O2(g) Catalyst Substance that speeds up a rxn without being consumed in the rxn • Provides a new pathway with lower Eathan original pathway • Faster rxn • Doesn’t change reactants or products

  6. Exothermic Reaction Pathway Heat of reactants Heat of the products

  7. Endothermic Reaction Pathway Heat of the products Heat of reactants

  8. KINETICS: RATE OF CHEMICAL REACTIONS: What affects the Rate of a Reaction? The rate of a reaction increases when the # of collisions increases. What changes may cause the # of collisions to increase? • Temperature: More KE = particles collide more often • Surface Area (Particle size): More exposed particles allowing more collision to occur • The presence of a catalyst: Lowers Ea (changes rxn pathway) = faster rxn • The nature of the reactants(s, l, g, aq): Size of reactants: high IE or shielding effect • Concentration: Higher concentrated solution have more particles = more collision

  9. Balancing Chemical Equations To follow the law of conservation of matter: Matter is not created or destroyed, ONLY CHANGED! Why balance chemical equations?

  10. Balancing Chemical Equations Coefficients • represent the # of molecules in the reaction (1 is never written) • smallest whole numbers Hydrogen gas (H2) can react with oxygen gas (O2) to form water (H2O) Note! Subscripts should never be changed when trying to balance a chemical equation

  11. Types of Reactions • Synthesis reactions • Decomposition reactions • Combustion reactions • Single displacement reactions • Double displacement reaction Some ways to classify may overlap!!!

  12. 1. Synthesis reactions Synthesis: meaning “to put together” Two or more reactants join together to form one single product reactant + reactant  1 product A + B  AB • Example: 2H2 + O2  2H2O • Example: C+ O2  CO2 or 2C + O2 → 2CO

  13. Synthesis Reactions Magnesium metal and oxygen gas combine to form the compound magnesium oxide. 2Mg(s) + O2→ 2 MgO(s)

  14. Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Na(s) + Cl2(g)  2Na(s) + Cl2(g)  2NaCl Solid Magnesium reacts with fluorine gas Mg(s) + F2(g)  Mg(s) + F2(g)  MgF2 Aluminum metal reacts with fluorine gas Al(s) + F2(g)  2Al(s) + 3F2(g)  2AlF3 NaCl MgF2 AlF3

  15. 2. Decomposition Reactions Opposite of synthesis rxn One single reactant, a compound, breaks apart into two or more simpler products One Reactant  Product + Product AB  A + B Example: 2 H2O  2H2 + O2 http://youtu.be/OTEX38bQ-2w

  16. heat Decomposition Reactions When mercury(II) oxide is heated, it decomposes or breaks down into two simpler substances. 2HgO(s) 2Hg(l) + O2(g)

  17. Practice Predict the products. Then, write and balance the following decomposition reaction equations: • Solid Lead (IV) oxide decomposes PbO2(s)  PbO2(s)  Pb(s) + O2 (g) • Aluminum nitride decomposes AlN(s)  2AlN(s)  2Al(s) + N2(g) Pb(s) + O2 (g) Al(s) + N2(g)

  18. 3. Combustion Reactions • oxygen reacts with another substance often producing energy in the form of heat and light • Burning!!! 1) A Fuel (hydrocarbon)2) Oxygen to burn it with3) Something to ignite the reaction (spark)

  19. Combustion Reactions of hydrocarbon Combustion of hydrocarbons will produce carbon dioxide and water In general: CxHy+ O2  CO2 + H2O Products: CO2 + H2O(incomplete burning does cause some by-products like CO)

  20. Combustion Practice: Predictthe products. Write and balance the following combustion reaction equations. C5H12 + O2 ANS: C5H12 + 8 O2 5 CO2 + 6 H2O C10H22 + O2  ANS: 2 C10H22 + 31 O2  20 CO2 + 22 H2O CO2 + H2O CO2 + H2O

  21. Do Now (pg-11) Write down the hints to ID the reaction. O2 is a reactant One product One reactant

  22. What happens when ionic compounds dissolve in water? Strong electrolyte: • each unit dissolved in water produces separated ions Ba(NO3)2 = Ba2+ & NO3-

  23. 4. Single Displacement Reactions Occur when one element replaces another in a reaction. A metal can replace another metal or H (+) OR A nonmetal can replace another nonmetal (-) element1 + compound1 element2+ compound2 A + BC  AC + B (if A is a metal/H+) OR A + BC  BA + C (if A is a nonmetal) (remember the cation always goes first!) When H2O splits into ions, it splits into H+ and OH-

  24. Single-Replacement Reactions • Dropping a small piece of potassium into a beaker of water creates the vigorous reaction. • 2K(s) + 2H2O(l) → 2KOH(aq) + H2

  25. Examples metals: Cu + 2AgNO3 Cu(NO3)2 + 2Ag metal + acid: Zn + 2HCl ZnCl2 + H2 metal + water: 2K + 2H2O  2KOH + H2 halogens: 2NaI + Cl2 2NaCl + I2 DON’T FORGET DIATOMIC ELEMENTS BrINClHOF

  26. Practice 1. Zinc metal reacts with aqueous hydrochloric acid Zn(s) + HCl(aq) Note: Zinc replaces the hydrogen ion in the rxn 2. Sodium chloride reacts with fluorine gas 2NaCl(aq) + F2(g)  2NaF(aq) + Cl2(g) Note: fluorine replaces chlorine in the compound 3. Aluminum metal reacts with aqueous copper (II) nitrate 2Al(s) + 3Cu(NO3)2(aq) 3Cu(s) + 2Al(NO3)3(aq) Note: Aluminum replaces copper 2 ZnCl2 (aq) + H2(g)

  27. 5. Double Replacement Reactions an exchange of ions between two ionic compounds (aqueous ONLY) Exchanges ions → forms new compounds AB + CD → AD + CB **A and C are the METALS, they must be written first

  28. Double Replacement Reactions Think about it like “foil”ing in algebra: Outer: first and last ions go together Inner: inside ions go together • Example: AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq) • Another example: K2SO4(aq) + Ba(NO3)2(aq)  2 KNO3(aq) + BaSO4(s)

  29. Practice Predict the products then balance the equation HCl(aq) + AgNO3(aq)  CaCl2(aq) + Na3PO4(aq)  FeCl3(aq) + NaOH(aq)  H2SO4(aq) + NaOH(aq)  AgCl(s) + HNO3(aq) NaCl(aq) + Ca3(PO4)2(s) 3 2 6 NaCl(aq) + Fe(OH)3(s) 3 3 Na2SO4(aq) + H2O(l) 2 2

  30. Closure Write down the hints to ID the reaction. Reactants are element + ionic compound/acid Reactants are ionic compound + ionic compound/acid

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