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MCAT - Chemistry > Class 5 > Flashcards

Class 5 Flashcards

1
Q

Is an acid more or less stable with the proton?

A

Without (think quarterback analogy–wants to give up the ball to reduce stress)

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2
Q

Is a base more or less stable with the proton?

A

With (think wide receiver analogy–unstable and stressed until receives the ball)

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3
Q

What is a better definition of acids/bases (Lewis or Bronsted)?

A

Lewis! Bases donate e-, are nucleophiles Acids accept e-, are electrophiles

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4
Q

Acids generally have ______ electronegative atoms bonded to H and bases generally have _____ electronegative atoms with lone pairs.

A

Acids = more EN atoms Bases = less EN atoms

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5
Q

Atoms without H can be acids if…

A

Electron deficient or with large positive charges

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6
Q

What is the KEY thing to have to be a base?

A

A lone pair!

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7
Q

What is it called when a compound has an acidic and basic functional group?

A

Amphoteric; can act as an acid or a base

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8
Q

Does size affect acid and base strength?

A

Yes. Acids are stronger if larger Bases are stronger if smaller

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9
Q

Rules for ranking acids/bases?

A
  1. Same structure, different charge: more charged acid/base will be stronger 2. Same row: more (acid)/less (base) EN will be stronger 3. Same column: larger (acids)/smaller (bases) size will be stronger
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10
Q

Do stronger acids favor the products or reactants?

A

Products. They dissociate more completely.

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11
Q

Do stronger bases favor the products or reactants?

A

Products. They “associate” more completely.

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12
Q

Do weak acids favor reactants or products?

A

Reactants

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13
Q

Do weak bases favor reactants or products?

A

Reactants

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14
Q

Ka > 1 means what?

A

Favors products (strong acid or strong base)

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15
Q

A strong acid will produce a _______ conjugate base

A

weak

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16
Q

Ka

A

Favors reactants (weak acid or weak base)

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17
Q

A weak base will produce a ______ conjugate base

A

strong

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18
Q

Name 7 strong acids

A

H2SO4

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19
Q

Name 7 strong bases

A

O2-

20
Q

Is ammonia a strong base?

A

Nope!

21
Q

Is water amphoteric?

A

Yes

22
Q

Do pure liquids and pure solids go into the equilibrium equations?

A

Nope

23
Q

Kw = ? = ? = ?

A

Ka x Kb = [H30+][OH-] = 1 x10^-14

24
Q

Ka and pKa are ______ proportional

A

Inversely

25
Q

pKa + pKb = ?

A

14

26
Q

pH + pOH = ?

A

14

27
Q

pH of a strong acid = ?

A

pH = -log[SA]

28
Q

When doing pH and “solving for logs” what is the only value to look for?

A

The exponent!! This is roughly equal to the pH! e.g. pH = -log(2.5 x10^-2) …so pH = - (-2)

29
Q

pH of a weak acid = ?

A

pH = -1/2log(Ka[WA])

30
Q

Can you ignore diprotic acids for weak acids?

A

Yes

31
Q

What is the Henderson-Hasselbach equation?

A

pH = pKa + log( [WB/WA] )

32
Q

What are buffers?

A

Mixtures of conjugate acid/base pairs.

33
Q

What is the log of 1?

A

0

34
Q

What do buffers do/how do they work?

A

Shift the reaction towards reactants or products to minimize changes in pH. CANNOT eliminate change however.

35
Q

What is the log of -1?

A

-1

36
Q

If your pH is less than your pKa, most of your substance will be ________.

A

protonated

37
Q

Neutralization reactions are always _____thermic.

A

Exothermic

38
Q

What are the 2 most typical products of a neutralization reaction?

A

Salt and water

39
Q

What is the clue that your titration curve is strong acid + strong base (or vice versa)?

A

The equivalence point is exactly 7.0 because the reaction yields pure water.

40
Q

A weak acid titration will yield an equivalence point of what?

A

Greater than 7 (a strong conjugate base)

41
Q

What is true at the half equivalence point?

A

pH = pKa

42
Q

A weak base titration will yield an equivalence point of what?

A

Less than 7 (a strong conjugate acid)

43
Q

In terms of anions, are Cl-, Br-, or I- ever basic?

A

No

44
Q

In terms of cations, are group I and II cations ever acidic?

A

No

45
Q

How do you choose an indicator?

A

You want to choose an indicator with a pKin within 1 unit of your pKa.

MCAT - Chemistry (7 decks)

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