Orgo txt 1.11

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Orgo txt 1.11
2013-08-31 20:57:00
Chapter One

CHM 201
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  1. Molecular formula
    gives the number of atoms of each element in one molecule of the compound
  2. Molecular formulas can be determined by a two-step process. The first step is __.
    determination of the empirical formula, the relative ratios of the elements present
  3. How to determine empirical formula.
    • 1) Out of 100 grams, convert the percentages to the numbers
    • 2) Divide the amount by their atomic mass to convert to moles (g/moles)
    • 3) Divide by the smallest number of moles obtained
  4. Molecular weights can be determined by methods that relate the __ or __ of a solvent to the __ of the unknown.
    • freezing point depression
    • boiling point evelation
    • molal concentration
  5. If the compound is volatile, what can we do.
    convert it to a gas and use its volume to determine the number of moles according to the gas law
  6. Arrhenius definition of acids and bases
    acids: substances that dissociate in water to give hydronium ions

    bases: substances that dissociate in water to give hydroxide ions
  7. Arrhenius equations correspond to what scale?
  8. Bronsted-Lowry acid and base definition
    acid: any species that donates a proton

    base: any species that accepts a proton
  9. One of the most important principles of the Bronsted-Lowry definition is this concept of __
    • conjugate acids and bases
    • NH3 is a base; its conjugate acid is NH4+
  10. What is Ka and its value?
    The stronger the acid...
    • acid-dissociation constant
    • value indicates the relative strength of the acid
    • the more it dissociates, the larger value of Ka
  11. Ka--> pKa
  12. For an acid to be strong, its conjugate base must be __. Therefore, it must be a __
    • stable in its anionic form
    • weak base
  13. In the reaction with an acid and base, the equilibrium generally favors the __
    weaker acid and base
  14. Equilibrium constant for the reaction of a base is called the __.
    base dissociation constant (Kb)
  15. Multiplying Ka and Kb should give you the __
    water ion-product constant (1 x 10^-14)
  16. True or False:
    Acid base reactions favor the stronger acid and the stronger base
    • True or False:
    • Acid base reactions favor the stronger acid and the stronger base

    weaker, weaker
  17. To be a Bronsted-Lowry acid, a compound must contain __.

    A strong acid must have __.
    • a hydrogen atom that can be lost as a proton.
    • a stable conjugate base after losing the proton
  18. The stability of the conjugate base is a good guide to __.
  19. More stable anions tend to be __, and their conjugate acids are __/
    • weaker bases
    • stronger
  20. Some of the factors that affect the stability of conjugate bases are __, __, and __.
    • electronegativity
    • size
    • resonance stabilization
  21. A more electronegative element bears what more easily, giving a more stable conjugate base and a stronger acid
    a negative charge
  22. The negative charge o an anion is more stable when?
    if it is spread over a larger region of space
  23. What is the periodic trend for acidity?
    increases down the column, as the size of the element increases
  24. The negative charge of a conjugate base may be __ over two or more atoms by __. Depending on how electronegative those atoms are, and how many share the charge, __ is often the dominant effect helping to stabilize an anion.
    • delocalized
    • resonance
    • resonance delocalization
  25. Acids are stronger if they __.
    lose a proton to give resonance-stabilized conjugate bases
  26. __ can also stabilize a conjugatebase through the __ of the molecule. Stabilization of the conjugate base results ina __ acid (__ value of pKa).
    • electron-withdrawing atoms and groups
    • sigma bonds
    • stronger
    • lower
  27. The magnitude of this __ depends on the nmber of bonds between __.
    • inducive effect
    • electronegative element and the site of the negative charge
  28. Stronger electron withdrawing groups stabilize the __ of the conjugate base more than weaker groups, leading to __.
    • anion
    • stronger acids
  29. Multiple electron-withdrawing grojups do what?
    increase the acidity more than a single group
  30. Lewis acid and base definitions
    • base: species with available electrons that can be donated to form new bonds
    • acid: species that can accept these electron pairs to form new bonds
  31. Since a Lewis acid accepts a pair of electrons, it is called an __. A Lewis base is called a __ because it donates electrons to a nucleus with an empty or easily vacated orbital.
    • electrophile
    • nucleophile
  32. True or False:
    Lewis acids and bases have nothing to do with protons.
  33. How do we distinguish Bronsted-Lowry acids and bases from Lewis acids and bases?
    Bronsted Lowry are simply referred to as acids and bases. Lewis acids are electrophiles and lewis bases are nucleophiles
  34. __ is used to show the flow of an electron pair __.
    • curved-arrow formalism
    • from the electron donor to the electron acceptor
  35. Electrons do not "flow" in resonance structures; they are __.
    simply delocalized