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Homework 9 posted and due Monday 4/2

Learn about classical reactions including metathesis and acid-base theories, with examples and net ionic reactions. Understand Arrhenius and Bronsted models of acids and bases. Discover the history and implications of classical reactions.

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Homework 9 posted and due Monday 4/2

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  1. Homework 9 posted and due Monday 4/2 Half-way through the week !

  2. CLASSICAL REACTIONs What to read… chapter 4 ( + a bit of Ch. 14) • Metatheses 131-140 • Acid-base 140-147; 549-552 • Oxidation-reduction 147-159

  3. Classical Reactions 1) Metathesis (double replacement) Complete Molecular reaction Pb(NO3)2 (aq) + 2KI(aq)  PbI2(s) + 2KNO3(aq) Complete Ionic Reaction Pb2+ +2NO3-+2K+ +2I- PbI2(s) + 2K+ +2NO3- Net Ionic Reaction Pb2+ + 2I-PbI2(s) METATHESIS REACTIONS (Two labs ago)

  4. CLASSICAL REACTIONs overview (continued) • Metathesis (double replacement) –continued Pb2+ + 2I-PbI2(s) Net ionic General characteristics • Ionic, aqueous salts are reactants • Product formed from cation swap is a solid • Low energy…no appreciable heat in/out

  5. Let’s practice one more on the board, kids ! (We already did this in lab….)

  6. CLASSICAL REACTIONs overview (continued) 2) Acid-base Complete Molecular reaction HCl(aq) + NaOH(aq) NaCl(aq) + HOH+ heat salt water acid base Last week’s lab Complete Ionic reaction H+ + Cl-+ Na+ +OH- Na+ + Cl-+H2O Net ionic reaction H+ + OH-  H2O `neutralization

  7. Demo reaction: ID the acid, base and salt below salt Acid Base H2SO4 + 2NaOH  Na2SO4 + 2H2O sodium hydroxide (essence of Lye) sodium sulfate (`Glauber’s Salt =laxative) Sulfuric acid (car battery acid) Complete ionic reaction? 2H+ + SO42-+2Na+ + 2OH- 2Na+ + SO42- +2H2O Net ionic reaction ? Let’s run this one 2H+ + 2OH-  2H2O

  8. CLASSICAL REACTIONs overview (continued) 2) Acid-base…- continued Net ionic reaction H+ + OH-  H2O General characteristics • Reactants are specially defined `acid’ and `base’ ionic solutions • Products are soluble salt and water • Significant heat is generated • Indicators signal endpts

  9. CLASSICAL REACTIONs overview (continued) Acid-Base Theories (pp 163-170, 652-655) 0) Pre-science: acids and bases are eternal opposites ACID+BASE= `BALANCE’ Positive + negative = null Hot + cold = just right Taoist version

  10. CLASSICAL REACTIONs overview (continued) Acid-Base Theories (pp 653-656) Modern Theory: Try #1 Svante Arrhenius: Father of the first modern acid/base theory Thesis on Acids & Bases derided by his research committee… Graduates with Ph.D ordinare (no distinction) see p. 144 Young Arrhenius (not considered promising) Old Arrhenius (wins Nobel prize in 1903 for same acidbase theory)

  11. CLASSICAL REACTIONs OVERVIEW(continued) A measure of this Ph.D `ordinaire’’s brilliance… In 1896 Arrhenius predicted green house gas (CO2) from profligate burning of the the newly popular fuel source …petroleum oil… would cause (gasp !) measurable and catastrophic global warming… …starting in 1990-2000 AD …the entire scientific establishment (and Standard Oil) laughed at him (again)

  12. FYI…. Until 2013 not a single current Republican member of the US Congress admitted that global warming is caused by burning of fossil fuels. The current President thinks it is a Chinese hoax perpetrated to make us less competitive

  13. Oil burning starts here

  14. There are currently 748 major fires burning in the US http://activefiremaps.fs.fed.us/

  15. CLASSICAL REACTIONs overview(continued) 1) Arrhenius Model =OH-donor BASE =H+ donor ACID HF HCl HBr HNO3 HClO4 H2SO4H2CO3 H3PO4 NaOH KOH NH4OH Ca(OH)2Mg(OH)2 Al(OH)3 Fe(OH)3

  16. CLASSICAL REACTIONs (continued) Acid-Base reactions ala’ Arrhenius: A+B= neutral HCl(aq) + NaOH(aq) NaCl(aq) + H2O H2SO4 + Mg(OH)2 MgSO4(aq) + 2H2O General rule for Arrhenius acid-base ACID+BASE= SALT + WATER

  17. CLASSICAL REACTIONs OVERVIEW continued) The `Inconvenient Truth’ about the Arrhenius model: basic salts EXAMPLE: Na2CO3 (sodium carbonate) No H+ or OH-….=> salt only

  18. CLASSICAL REACTIONs OVERVIEW(continued) The `Inconvenient Truth’ about the Arrhenius model: basic salts (continued) EXAMPLE: Na2CO3 (sodium carbonate) experimental results of adding to water: • Turns pink in presence of phenolphthalein • gas-forming reaction with HCl, pink disappears Where’s OH ??? => A base !!!!?????

  19. CLASSICAL REACTIONs OVERVIEW (continued) The `Inconvenient Truth’ about the Arrhenius model: basic salts (continued) Other examples of `basic’ salts Na3PO4 K2SiO3 NaC2H3O2 Basic salts cannot be rationalized using Arrhenius’ acid/base model

  20. CLASSICAL REACTIONs (continued) Bronsted to the rescue… Winner of the Bronsted look alike contest…. Young Bronsted…Swedish chemist circa 1910… Young James Dean…American actor circa 1955…(“Rebel Without a Cause,”“East of Eden”, “Giant” ) Bronsted a few years after marriage and kids

  21. CLASSICAL REACTIONs OVERVIEW(continued) BronstedModel of Acids/Bases3 new concepts (see pp 452-453 & 623-6) New Concept #1: Follow the protons Acid= proton donor (=H+) No real change from Arrhenius HF, HCl, HBr HNO3 HClO4 H2SO4 H2CO3 H3PO4 ARRHENIUS ACIDS = BRONSTED ACIDS

  22. CLASSICAL REACTIONs OVERVIEW(continued) BRONSTED’S MODEL OF ACIDS/BASES:New Concept #1: following the protons (cont.) BASE= proton acceptor Examples of Bronsted Bases OH- CO3-2 ,PO4-3, C2H3O2-,SiO3-2… The set of Bronsted bases includes Arrhenius bases + …. …nearly any negative ion (=anion) that even weakly attracts protons

  23. CLASSICAL REACTIONs OVERVIEW(continued) BRONSTED’S MODEL OF ACIDS/BASES:New Concept #2 How the proton acceptor creates the basic salt effect: Hydrolysis…Bronsted bases `split’ water !!! EXAMPLE CO32- + H-OH  HCO3- + OH- Hydrolysis reaction ..Bronsted Base is basic in water because it splits water to make OH-!

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