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Lewis structure

Lewis structure. Relevant shape?. shape name?. Bent structure. Nitrite anion. TETRAHEDRON. Sulfuric acid. Lewis structure. Relevant shape?. shape name?. Trigonal bipyramid. Sulfur tetrafluoride. Square pyramid. 1 lone pair + 4 bonds. U-try-It now…. Lewis structure.

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Lewis structure

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  1. Lewis structure Relevant shape? shape name? Bent structure Nitrite anion TETRAHEDRON Sulfuric acid

  2. Lewis structure Relevant shape? shape name? Trigonal bipyramid Sulfur tetrafluoride Square pyramid 1 lone pair + 4 bonds

  3. U-try-It now…

  4. Lewis structure Relevant shape? shape name? Trigonal plane formaldehyde LINEAR carbon dioxide

  5. Lewis structure Relevant shape? shape name? Bent structure Nitrite anion TETRAHEDRON Sulfuric acid

  6. Lewis structure Relevant shape? shape name? Trigonal bipyramid Sulfur tetrafluoride Square pyramid 1 lone pair + 4 bonds

  7. U-Predict-it From scratch… SO2 SO3 SO42-  MOLECULAR SHAPE VSEPR THEORY PREDICTS Bent Trigonal plane pyramid THEORY 120O 120O 109.5O 108.7O 120O 1experiment 119.5O 1From NIST COMPUTATIONAL COMPARISON DATA BASE (ccDB)

  8. Our chemistry road trip so far… 2)Compounds & Reaction Math the `foundation’ of chemistry (SLO #1,4,5) Unit/conversion review Dalton’s law of multiple proportions Compound formulas & Periodic Table Naming (lab) Mole concept % composition Reaction balancing Stoichiometry, limiting yield, % yield 1)Atomic structure(SLO #2) Rutherford atom Bohr atom spdf model Quantum theory Periodic table spectroscopy 3)Molecular structure(SLO #3) Ionic compounds Lewis rule of 8 Lewis octet rule and beyond VSEPR ????

  9. And now (after many weeks of &^%!! Moles and Lewis)…. ….. ….for something completely different…. 4) CLASSICAL REACTIONs

  10. Today’s Student Learning Objective (SLO): Students will be able to: write, balance, identify and predict common reaction classes (metatheses, acid-base,redox). SLO #6 Translation: What happens when I add this to that ?

  11. CLASSICAL REACTIONs (continued) What to read… chapter 10 ( + a bit of Ch. 14) • Metatheses 443-452 • Acid-base 452-458; 623-625 • Oxidation-reduction 458-466

  12. Classical Reactions:an overview • 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) PRACTICE FOR WRITING BALANCED METATHESIS REACTIONS AS ABOVE DONE DURING LAB

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

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

  15. 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

  16. CLASSICAL REACTIONs overview (continued) Acid-Base Theories (pp 136-44, 625-8) 0) Pre-science: acids and bases are eternal opposites ACID+BASE= `BALANCE’ Positive + negative = null Hot + cold = just right Taoist version

  17. CLASSICAL REACTIONs overview (continued) Acid-Base Theories (pp623-625) Modern Theory: Try #1Svante Arrhenius: Father of the first modern acid/base theory Thesis on Acids & Bases derided by his research committee… Graduates with Ph.Dordinare (no distinction) Young Arrhenius Old Arrhenius (wins Nobel prize for same acidbase theory)

  18. CLASSICAL REACTIONs OVERVIEW(continued) A measure of this Ph.D `ordinaire’’s brilliance… In 1896 Arrhenius predicted the 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)

  19. FYI…. Not a single current Republican member of the US Congress has yet to admit that global warming is caused by burning of fossil fuels.

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

  21. 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

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

  23. 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 !!!!?????

  24. 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

  25. CLASSICAL REACTIONs (continued) Bronstedto 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

  26. 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

  27. 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

  28. 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-!

  29. BRONSTED’S MODEL OF ACIDS/BASES:New Concept #3a: conjugate acid/base pairs Conjugate idea is like going drag… Men=acid Women=base Identify `acids’ and bases CONJUGATE ACID CONJUGATE BASE BASE ACID

  30. CLASSICAL REACTIONs OVERVIEW(continued) BRONSTED’S MODEL OF ACIDS/BASES:New Concept #3a: conjugate acid/base pairs Identify `acid’ and base Identify conjugateacid and base Conjugate acid  HCO3- + OH- CO32- + H-OH Acid Base Conjugatebase Acid conjugatebase Base conjugate acid

  31. new concept #3a: Conjugates (continued) When acid and base reacts…. Acid conjugate base Base conjugate acid PO43- + HCO3- HPO42- + CO32- conjugate base conjugate acid acid base EXAMPLE: IDENTIFY ACID, BASE AND THEIR CONJUGATEBASE AND ACID ABOVE

  32. CLASSICAL REACTIONs OVERVIEW(continued) BRONSTED’S MODEL OF ACIDS/BASES:New Concept #3b: Bronsted Model ACID + BASE CONJUGATE BASE + CONJUGATE ACID • spontaneous acid + base reactions • produce weaker acids + bases Contrast to Arrhenius Model ACID + BASE SALT +WATER Both products `neutral’

  33. ACID-BASE THEORIES SUMMARIZED ARRHENIUS BRONSTED PROTON DONOR ACID = H+DONOR BASE= OH- DONOR PROTONDONOR ACID + BASE SALT + WATER CONJUGATE ACID + CONJUGATE BASE

  34. What observation required Bronsted to create a new Acid/Base Theory different than Arrhenius’s model ? • Many salts formed conjugate acids. • Spontaneous acid+base reactions only occurred if weaker acids and bases formed. • H2O spontaneously decomposed to OH- and H+ in presence of various salts. • Many salts without OH- somehow created OH- in water.

  35. Which part of the Bronsted salt K3PO4 is the proton acceptor ? • K+ • O2- • P3- • PO43- • K3PO4 • OH-

  36. What new concept of Bronsted’smostdirectly explains why many salts are bases? • The anionic part of salts can hydrolyze water. • Spontaneous acid/base reactions lead to weaker conjugate acids/bases. • Bronsted bases are proton acceptors. • Bronsted acids are proton donors.

  37. In-class reaction Jeopardy WHAT IS… Low heat, precipitates, cation swap metathesis Pick the Arrhenius acids H2O HNO3 NaHCO3HBrNaCl HNO3HBr Na2CO3 for example A Bronsted base What’s my reaction type: Acid/base neutralization (Arrhenius) HCl + KOH KCl + H2O

  38. In-class reaction Jeopardy WHAT IS… What’s my reaction type: Acid/base hydrolysis (Bronsted) K3PO4 + H2O  HK2PO4 + KOH Write my products ? AgNO3(aq) + NaCl(aq) ????? AgCl(s) + NaNO3(aq) Pick the Bronstedbase(s) NaOH NaHCO3 K3PO4 Pick the Arrhenius bases NaOHHBr NaHCO3 K3PO4 NaOH

  39. Practice with Bronsted model and language 1) Identify the Bronsted bases in this list: HBrNaOH Na2CO3NH4Cl K3PO4 NaCl base base acid base base acid 2) Identify the acid (A), base (B) and the conjugate acid (CA) and conjugate base (CB) in the two reactions below 1) Na2CO3 + H3PO4 NaHCO3 + NaH2PO4 B A CA CB 2) KCN + H2O HCN + KOH B A CB CA 3) What is the hydrolysis reaction that occurs with PO43- ? HPO42- + OH- PO43- + H2O

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