# Orgo txt 1.11

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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?
pH
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
-log10Ka
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 __.
acidity
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.
True
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
 Author: DesLee26 ID: 232189 Card Set: Orgo txt 1.11 Updated: 2013-09-01 00:57:00 Tags: Chapter One Folders: Description: CHM 201 Show Answers: