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Kaplan General Chemistry > Ch. 10: Acids and Bases > Flashcards

Ch. 10: Acids and Bases Flashcards

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1
Q

how does an Arrhenius acid behave

A

Arrhenius acids dissociate to form an excess of H+ in solution

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2
Q

how does an Arrhenius base behave

A

Arrhenius base dissociate to form an excess of OH- in solution

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3
Q

how does a Bronsted-Lowry acid behave

A

Bronsted-Lowry acids are PROTON (H+) donors

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4
Q

how does a Bronsted-Lowry base behave

A

Bronsted-Lowry bases are PROTON (H+) acceptors

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5
Q

how does a Lewis acid behave

A

Lewis acids are ELECTRON pair acceptors

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6
Q

how does a Lewis base behave

A

Lewis bases are ELECTRON pair donors

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7
Q

what is an amphoteric species? how does it behave?

A

reacts like…

  • an acid in a basic environment (donating proton, accepting electron)
  • a base in an acidic environment (acceptation proton, donating electron)

WATER

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8
Q

how is water an amphoteric species

A

acts like an acid (donates proton) in a base
H2O + B- HB + OH-

acts like a base (accepts proton) in an acid
HA + H2O A- + H3O+

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9
Q

what is an amphiprotic species

A

species that can either gain or lose a proton

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10
Q

what occurs during autoionizations

A

amphoteric species react with themselves to yield basic AND acidic ions

H2O + H2O -OH + H3O+

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11
Q

what is the water dissociation constant, Kw

A

Kw = [H3O+][OH-] = 10^-14 at 25C (298K)

when autoionizied, the concentrations of H3O+ and OH- will always equal 10^-14 at 25C

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12
Q

what properties is Kw dependent on

A

like all equilibrium constants, Kw is dependent only on temperature. Changes to concentration, pressure, and volume will not effect Kw

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13
Q

what do pH and pOH scales measure

A

the concentrations of H+ and -OH ions in concentration on a negative logarithmic scale

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14
Q

what is the equation for the pH of a solution

A

pH = - log[H+] = log 1/[H+]

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15
Q

what is the equation for the pOH of a solution

A

pOH = -log[-OH] = log 1/[-OH]

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16
Q

what does pH + pOH =

A

pH + pOH = 14

as pH increases, pOH decreases by the same amount and vice versa

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17
Q

what is the approximate pvalue for n * 10^-m

A

p value ~ m - 0.n

ex: Ka = 1.8 * 10^-5 … pKa ~ 5 - 0.18 ~ 4.82

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18
Q

how are strong acids and bases different than weak acids and bases

A

strong acids/bases completely dissociate into their component ions in aqueous sol’ns

weak acid/bases partially dissociate into their component ions

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19
Q

what does log 1 =

A

log 1 = 0

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20
Q

what does log 10 =

A

log 10 = 1

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21
Q

what is the equation for an acid dissociation constant, Ka

A

HA + H2O H3O+ + A-

Ka = [H3O+][A-] / [HA]

WATER IS PURE LIQUID, NOT INCLUDED

22
Q

what is the equation for a base dissociation constant, Kb

A

BOH B+ + -OH

Kb = [B+][OH-]/[BOH]

WATER IS PURE LIQUID, NOT INCLUDED

23
Q

what do Kb and Ka values less than one indicate

A

weak bases and acids

24
Q

what kind of acid-base reaction occurs in conjugate pairs

A

bronsted-lowry acid-base reaction

base + conjugate acid
acid + conjugate base

25
Q

what is a conjugate acid

A

acid formed when a BL base accepts a proton

26
Q

what is a conjugate base

A

base formed when a BL acid donates a proton

27
Q

equation for dissociation constants of conjugate pairs

A

Ka, acid * Kb, conjugate base = Kw = 10^-14

Kb, base * Ka, conjugate acid = Kw = 10^-14

28
Q

how are Ka and Kb values related

A

inversely

when one value is high, the other value is low

29
Q

how do electronegative elements affect acid strength

A
  • increases acidity*
  • electronegative substituents positioned near an acidic proton pull electron density out of the acidic bond
  • facilitates dissociation of the acidic hydrogen
30
Q

what occurs during a neutralization reaction

A

an acid and a base are reacted together to form a salt and water

HA + BOH BA + H2O

31
Q

what occurs during a hydrolysis reaction

A

water and a salt are reacted together to form an acid and a base

32
Q

what is an acid equivalent equal to

A

one mole of H+ ions (H3O+)

33
Q

what is a base equivalent equal to

A

one mole of OH- ions

34
Q

what does it mean to be polyvalent/polyprotic

A

each mole of acid or base liberates more than one acid or base equivalent

35
Q

what is the purpose of titration

A

to determine the concentration of a known reaction in a solution

36
Q

how are titrations performed [big picture]

A

small volumes of a solution with known concentration [titrant] are added to a known volume of a solution with unknown concentration [titrand] until the complete of the reaction is achieved at an equivalence point

37
Q

when is the equivalence point reached in acid base titration

A

when the number of acidic equivalents present in the original solution equals the number of base equivalents added (or vice versa)

38
Q

what equation relates normalities with volumes for titrations

A

NaNb = VaVb

where N is normality (equivalents added) and V is volume of the solutions

39
Q

what are indicators

A

weak acids or bases that have different colors in their protonate and deprotonated states

binding/release of a proton –> change in absorption spectrum –> perceived change in color

40
Q

what occurs at the endpoint

A

the indicator changes to its final color

41
Q

what makes a particular indicator a good choice for a titration

A
  • weak acid/base

- Kb or Ka is lower than what is being titrated

42
Q

where is the equivalence point for a strong acid/strong base titration

A

pH = 7

43
Q

where is the equivalence point for a weak acid/strong base titration

A

pH > 7

reaction between weak acid a strong base produces weak conjugate base and VERY weak conjugate acid –> greater concentration of [-OH] at equilibrium

44
Q

where is the equivalence point for a strong acid/weak base titation

A

pH < 7

rxn between strong acid and weak base produces weak conjugate acid and VERY weak conjugate base –> greater concentration of [H+] at equilibrium

45
Q

where is the equivalence point of a weak acid/weak base titration

A

near neutral pH

both species will partially dissociate

46
Q

what is a half equivalence point

A

point on a titration curve where half of a given species has been protonated/deprotonated

47
Q

what is a buffer solution made of

A

a weak acid/base and its salt

ex: acetic acid (CH3COOH) and sodium acetate (Ch3COO-Na+)
ammonia (NH3) and ammonium chloride (NH4+Cl-)

48
Q

what is useful about a buffer

A

resist changes in pH when small amounts of acid/base are added to the solution and can neutralize additions of charged compounds

49
Q

equation for pH of a weak acid buffer solution

A

pH = pKa + log [A-] / [HA]

50
Q

equation for pOH of a weak base buffer solution

A

pOH = pKb + log [B+] / [BOH]

51
Q

what is the pH or pOH when [acid/base] = [conjugate]

A

log [1] = 0 so…

  • pH = pKa
  • pOH= pKb
52
Q

what is the buffering capacity and how does it change?

A

it is the ability to which the buffer system can resist changes in pH

increase with higher concentration ratios of acid/base to conjugate and decreased with lower concentrations

Kaplan General Chemistry (9 decks)

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