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Chemistry Lecture > Exam Three > Flashcards

Exam Three Flashcards

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1
Q

Acid (general):

A

substance that donates a proton

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2
Q

Base (general):

A

substance that accepts a proton

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3
Q

Arrhenius classifies an HA and B based on…

A

their behavior in water

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4
Q

Arrhenius HA:

A
  1. substance with H in its formula that dissociates in water to yield H3O+
  2. never contain discrete H+ ions; contain covalently bonded H atoms that ionize when molecules of the acid dissolve in water
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5
Q

When an HA and B react they undergo […].

A

neutralization

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6
Q

In Arrhenius sense, when does neutralization occur?

A

H+ (HA) + OH- (B) form H2O

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7
Q

No matter which strong HA and B react, no matter which salt results, the enthalpy is always…

A

-55.9 kJ per mole of water formed

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8
Q

What are some typical Arrhenius HA/B?

A

HA: HCl, HNO3, HCN

B: NaOH, KOH, Ba(OH)2

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9
Q

Bronsted-Lowry HA:

A
  1. HA is a proton donor, any species that donates an H+ ion
  2. An HA must contain H in its formula
  3. All Arrhenius HA are BL HA
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10
Q

Bronsted-Lowry B:

A
  1. B is a proton acceptor, any species that accepts an H+ ion
  2. B must contain a lone pair of electrons to bind H+
  3. All Arrhenius B are BL B, but not all BL B are Arrhenius B
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11
Q

How does a conjugate acid differ from its conjugate base?

A

conjugate HA has one more H than its conjugate B

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12
Q

Amphiprotic:

A

substance that can act as a base and an acid

**water

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13
Q

Conjugate Base:

A
  1. results when an HA donates H+

2. has one fewer H and one more negative charge than the acid

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14
Q

Conjugate Acid:

A
  1. results when a base gains H+

2. has one more H and one fewer negative charge than the base

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15
Q

T/F: Conjugate HA and B may be neutral, a cation, and an anion.

A

true; dependent on its initial charge and reaction

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16
Q

In a Bronsted-Lowry HA/B reaction, equilibrium will favor the […] if the reacting HA/B are strong. The reaction will always favor the formation of the […] acid and base.

A

products; weaker

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17
Q

Why does equilibrium favor the formation of weaker HA/B?

A

weaker means they are more stable

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18
Q

An acid donates a proton to form its conjugate […], which therefore has one less […] atom and one more […] charge than its acid.

A

base; H; negative

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19
Q

pH of a solution is a measure of its […] concentration.

A

H3O+ ion

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20
Q

What is the value of Kc in a dilute solution of a strong acid?

A

extremely large; way above 1

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21
Q

Strong HA are therefore strong […].

A

electrolytes

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22
Q

What are the two types of strong acids?

A
  1. hydrohalic acids (HCl, HBr, HI)
  2. Oxoacids (HNO3, H2SO4, HClO4)

**number of O atoms exceeds the number of ionizable protons by two or more

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23
Q

Strong Bases:

A
  1. Group 1A OH

2. Heavy Group 2A OH

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24
Q

Water-soluble compounds containing […] or […] ions are strong bases.

A

O2-; OH-

M2O or MOH
MO or M(OH)2

where M is G1 or heavy G2

25
Q

Can pH values be negative?

A

yes

26
Q

T/F: A strong HA always produces a concentrated aqueous solution.

A

false; “strong” refers to the degree of dissociation, not the concentration of HA in water

27
Q

T/F: Strong acid molecule not present in aqueous solutions.

A

true they completely dissociate

28
Q

T/F: Strong acid molecules hydrogen bond to water molecules in aqueous solution.

A

false; covalently bond

29
Q

General reaction for weak HA dissociation:

A

HA + H2O H3O+ + A-

30
Q

In a dilute solution of a weak acid…

A
  1. HA molecules are undissociated, so [HA]eq = [HA]init
  2. only a very small number of HA molecules dissociate, so [H3O+] = [A-] &laquo_space;[HA]init
  3. value of Kc is very small
31
Q

Equilibrium expression of a weak acid:

A

T: [H3O+][A-]

B: [HA]

Ka = T/B

32
Q

The stronger the HA, the higher the […] is at equilibrium. and the larger the value of […].

A

[H3O+]; Ka

33
Q

As the initial concentration of a weak acid decreases, the percent dissociation of the acid […].

A

increases

increase in volume shifts the equilibrium position to favor more moles of ion

34
Q

Polyprotic acids:

A

acids with more than one ionizable proton

35
Q

Polyprotic acids Ka value trend:

A

Ka1»Ka2»Ka3

it is more difficult for the positively charges H+ ion to leave a singly charged anion than to leave a neutral molecule

36
Q

HA strength: Going across a PT.

A

EN increases so acidity increases

37
Q

HA strength: Going down a PT.

A

bond strength decreases so acidity increases

38
Q

What are the two factors that determine how easily a proton is released from a nonmetal hydride:

A
  1. EN of the central nonmetal

2. strength of the EH bond

39
Q

If an oxoacids has more O within the substance, the HA strength…

A

increases

40
Q

If a group of oxoacids have the same number of O atoms What would differentiate them by strength?

A

central atom (E) EN

the higher the EN the higher the HA strength

41
Q

What type of metal ions are acidic in water?

A

small, highly charged metal ions

42
Q

Why is it that only a certain type of metal ions are acidic in water?

A

they withdraw electron density from the OH bonds of bound H2O molecules, releasing an H ion to the solution

43
Q

What are the factors that affect the ease with which a proton is released from a nonmetal hydride?

A
  1. strength of the EH bond

2. the EN of the central atom

44
Q

What is the strength and character (HA/B) of anions of weak polyprotic acids?

A

weak bases

** CH3COO and PO4

45
Q

How can a salt yield a neutral solution?

A

consists of an anion of a strong acid and the cation of a strong base; ions do not react with water

46
Q

Salt: Yielding of an acidic solution consists of…

A

anion of a strong acid and the cation of a weak base

47
Q

What causes a solution to become neutral?

A

neutralization occurs; complete dissociation (no weak HA/B)

48
Q

Lewis Acid:

A

low density electron density that accepts an electron pair

low density due to electron deficiency or polar bond

49
Q

Describe the solution containing a salt of the cation of a strong base and the anion of a polyprotic acid.

A
  1. anion will hydrolyze to produce either H3O+ and OH- ions depending on the relative values of Ka and Kb
  2. cation has no impact on the pH
50
Q

Adduct:

A

hydrated metal cation

51
Q

Metal cations act like a […] when dissolved in water.

A

Lewis HA

52
Q

What are the components of a buffer?

A

conjugate acid-base pair; weak acid and CB or weak base and CA

53
Q

How do buffers work?

A

common-ion effect; the shift in the position of an ionic equilibrium away from an ion involved in the process that is caused by the addition or presence of that ion

54
Q

T/F: The buffer capacity will be higher if more concentrated solutions are used.

A

true

55
Q

T/F: The pKa of the acid component of the buffer should be close to the desired pH.

A

true

56
Q

T/F: The pH of the buffer will depend on the absolute concentrations of the acid and base solutions used.

A

false; the relative concentrations of these solutions that will determine buffer pH

57
Q

What are the two factors that affect buffer capacity?

A
  1. the closer the ratio [HA]/[A-] is to 1, the higher the buffer capacity
  2. the more concentrated the buffer components, the greater the buffer capacity
58
Q

What are the steps for preparing a buffer solution?

A
  1. choose an appropriate CA/CB pair
  2. use pH and pKa to determine the desired ratio of buffer component concentrations
  3. convert the ratio to find the concentration of the two buffer components
  4. mix the components together

Chemistry Lecture (7 decks)

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