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Double Bond: C 2 H 4

Double Bond: C 2 H 4. An sp 2 hybridized C atom has one electron in each of the three sp 2 lobes. Side view of the sp 2 hybrid + the unhybridized p orbital. Top view of the sp 2 hybrid. Double Bond: C 2 H 4.

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Double Bond: C 2 H 4

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  1. Double Bond: C2H4 • An sp2 hybridized C atom has one electron in each of the three sp2 lobes Side view of the sp2 hybrid + the unhybridized p orbital Top view of the sp2 hybrid

  2. Double Bond: C2H4 • Two sp2 hybridized C atoms plus p-orbitals in proper orientation to form a C=C double bond

  3. Double Bond: C2H4 • The portion of the double bond formed from the head-on overlap of the sp2 hybrids is designated as a s bond • The other portion of the double bond, resulting from the side-on overlap of the p orbitals, is designated as a p bond

  4. Triple Bond: C2H2 A  bond results from the head-on overlap of two sp hybrid orbitals

  5. Triple Bond: C2H2 • The unhybridized p orbitals form two p bonds • Note that a triple bond consists of one  and two p bonds

  6. CHAPTER 10 • Reactions in Aqueous Solutions I: Acids, Bases, and Salts

  7. The Arrhenius Theory • Acids are substances that contain hydrogen and produce H+ cations in aqueous solutions • Bases are substances that contain a hydroxyl group and produce OH– anions in aqueous solutions • These two statements represent the Arrhenius theory of acids and bases

  8. The BrØnsted-Lowry Theory • This theory is more general than the Arrhenius theory • An acid is a proton donor (H+) • A base is a proton acceptor NH3(aq) + H2O(l)  NH4+(aq) + OH–(aq) base acid • Notice, that according to the Arrhenius theory NH3 is not a base

  9. The Hydronium Ion • The protons (H+) are never present in solution by themselves • Protons are always hydrated that is surrounded by several water molecules • We don’t know exactly how many • H+(aq) is really H(H2O)n+ • Where n is a small integer • We normally write the hydrated hydrogen ion as H3O+ and call it the hydronium ion

  10. The BrØnsted-Lowry Theory • Acid-base reactions are the transfer of a proton from an acid to a base NH3(aq) + HCl(aq)  NH4+(aq) + Cl–(aq) base acid HCl(aq) + H2O(l)  H3O+(aq) + Cl–(aq) acid base

  11. Conjugate Acid-Base Pairs HF(aq) + H2O(l)  H3O+(aq) + F–(aq) • Two species that differ by a proton are called conjugate acid-base pairs • Such conjugate pairs will exist for each acid-base reaction acid base acid base • HF is a weak acid and it does not ionize completely in aqueous solutions • This reaction also proceeds in the reverse direction (it is reversible)

  12. Conjugate Acid-Base Pairs • To find a conjugated base: • Add 1 proton (H+) to the acid • Increase the total charge by 1 • To find a conjugated acid: • Remove 1 proton from the base • Decrease the total charge by 1 H2O NH3 CH3COO– CH3COOH

  13. Conjugate Acid-Base Pairs HF(aq) + H2O(l) H3O+(aq) + F–(aq) acid1 base2 acid2 base1 • HF is a weak acid and ionizes only slightly • It prefers to exist as HF(aq) rather than F–(aq) • This means that F–(aq) has higher affinity to the proton than H2O (it holds the proton stronger) • Another way to put it is to say that F–(aq) is a stronger base than H2O • H3O+(aq) gives up the proton easier than HF(aq) and therefore it is a stronger acid than HF(aq) (it is more prone to loosing the proton)

  14. The BrØnsted-Lowry Theory • Important conclusion: • Weak acids have strong conjugate bases • Weak bases have strong conjugate acids • The weaker the acid or base, the stronger the conjugate partner • Another example: ammonia in water

  15. Properties of Acids • Solutions of acids have a sour taste • Don’t taste them in the lab !!! • They change the colors of many indicators • Acids turn blue litmus to red • Acids turn bromothymol blue from blue to yellow • They react with metals to generate hydrogen gas, H2

  16. Displacement Reactions • Displacement reactions occur when one element displaces another element from a compound: Zn + H2SO4 ZnSO4 + H2 • Total and net ionic equations: • Not all the metals are capable of displacing hydrogen from an acid

  17. Metal Activity Series • Active enough to displace hydrogen from an acid • More active Li, K, Ca, Na, Mg, Al, Mn, Zn, Fe, Co, Ni, Pb,H,Cu, Hg, Ag, Pt, Au • Less active • Cannot displace hydrogen from an acid

  18. Example 1 • Write reactions between the following metals and HCl solution. Write total and net ionic equations in each case • Fe, Na, Pt, Ni, Cu

  19. Example 1 (continued) • Write reactions between the following metals and HCl solution. Write total and net ionic equations in each case • Fe, Na, Pt, Ni, Cu

  20. Metal Activity Series • The more active metal will always displace the less active metal from the solution of its salt: Cu + 2AgNO3 Cu(NO3)2 + 2Ag

  21. Example 2 • Write reactions between the following substances in aqueous solutions: • Zn + CuSO4 • Hg + Fe(NO2)3 • Mg + Hg(NO3)2 • Al + Fe(NO3)3

  22. Example 2 (continued)

  23. Assignments & Reminders • Go through the lecture notes • Read Chapter 10 completely • Read Section 4-10 of Chapter 4 • Monday (10/31) and Tuesday (11/1) – lecture quiz #5 (Chapter 8) • Homework #5 is due by Monday (10/31)

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