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Chemistry > Acids and Bases > Flashcards

Acids and Bases Flashcards

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1
Q

define a bronsted-lowry acid

A

it is a proton donator/H+ donor

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2
Q

define a bronsted-lowry base

A

it is a proton acceptor/H+ acceptor

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3
Q

define a amphiprotic species

A

it is a species that is able to both donate and accept a proton, and thus able to react both as an acid and a base

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4
Q

define a amphoteric species

A

a species that can act as both acid and base

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5
Q

what is a dative bond

A

where both the valence electrons from a molecule is donated to the bond

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6
Q

is H+ the same as H3O+

A

yes

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7
Q

HCl + NH3 ––> NH4+ + Cl-
what is the acid and the conjugate base?

A

HCl = acid
Cl- = conjugate base

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8
Q

acid + base ––>

A

salt + water (H20)

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9
Q

what are alkalis?

A
  • substances which form OH- ions in solution when they dissolve
  • soluble bases
  • all alkalis are bronsted-lowry bases
  • but not all bronsted-lowry bases are alkalis
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10
Q

what colour is litmus in acid

A

red

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11
Q

what colour is litmus in base

A

blue

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12
Q

what colour is methyl orange in acid

A

red

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13
Q

what colour is methyl orange in base

A

yellow

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14
Q

what colour is phenolphthalein in acid

A

colourless

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15
Q

what colour is phenolphthalein in base

A

pink

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16
Q

acid + metal ––>

A

salt + hydrogen

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17
Q

acid + carbonate ––>

A

salt + water + carbon dioxide (CO2)

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18
Q

acid + metal oxide (base) ––>

A

salt + water (H2O) (ionic, made up of ions)

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19
Q

equation for pH

A

pH = –log [H3O+]
or
pH = –log [H+]

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20
Q

what units does pH have

A

none

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21
Q

[H+] =

A

10^(–pH)

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22
Q

what does a one unit change in the pH mean

A

there has been a 10-fold change in [H+]

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23
Q

what does a change from pH 7 to pH 11 mean in terms of [H+]?

A

40x decrease in [H+]

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24
Q

[H3O+]*[OH–] =

A

Kw

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25
Q

what is [H+] best written as?

A

[H3O+]

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26
Q

what is the pH a measure of

A

the concentration of [H+]

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27
Q

what happens at pH 7 (in terms of the concentration of [H30+] and [OH–])

A

there is equal amounts of [H3O+] and [OH–], it is neutral

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28
Q

in acids, there are _____ [H+] ions than [OH-]

A

more

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29
Q

in bases, there are _____ [H+] ions than [OH-]

A

less

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30
Q

when neutral, [H3O+] ____ [OH–]

A

equals

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31
Q

Kw =

A

10^(–14) = [H3O+]*[OH–] at (25ºC)

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32
Q

what are the units for concentration

A

moldm^(-3)

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33
Q

what concentration is considered a concentrated acid?

A

anything above 1moldm^(-3)

> 1moldm^(-3)

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34
Q

what is the definition of a concentrated acid

A

an acid that doesn’t have acid like properties
ie. it doesn’t turn litmus paper red, do not release hydrogen gas from metals, do not release carbon dioxide from carbonates etc.

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35
Q

what does the size of Kw tell us about the ionisation of a compound/molecule?

A
  • a small value represents that the reaction has mostly reactants
  • a large value represents that the reaction is mostly products
  • therefore there is are ions when Kw is larger vice versa
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36
Q

what is Kw?

A

it is the ionic product of water

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37
Q

pH+pOH =

A

14

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38
Q

what is the definition of a dilute acid

A

an acid that is in water and has dissociated into H3O+ ions to give acid like properties

H3O+ is:
- what turns litmus red
- releases CO2 form carbonates
- makes excellent electrical conductors

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39
Q

definition of strong acids

A

strong acids ionise completely in solution

they transfer all of their protons to water
(H2O + H+ ––> H3O+)

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40
Q

what size is the equilibrium constant when acids are strong? and what does it tell you about the position of the equilibrium?

A

large and the equilibrium lies to the right

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41
Q

definition of weak acids

A
  • weak acids will transfer a few protons to water
  • only a small portion of acid will turn into ions, most will remain as molecules
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42
Q

what do weak acids have?

A

carbon

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43
Q

how do you identify a weak acid?

A

carbon is present in the acid

44
Q

what size is the equilibrium constant when acids are weak? and what does it tell you about the position of the equilibrium?

A

the equilibrium constant is small and it lies to the left because it is mostly reactants

45
Q

how do you write a Ka expression for
CH3COOH + H2O ––> CH3COO– + H3O+

A

Ka= products / reactants

= [CH3COO–] [H3O+] / [CH3COOH]

you do not include liquids in K expressions

46
Q

definition of weak base

A
  • it doesn’t ionise fully
  • it only ionises partially
  • equilibrium lies to the left
  • Kb value is low/small
47
Q

definition of strong base

A
  • it ionises fully
  • equilibrium lies to the right
  • Kb value is high/large
48
Q

strong acids and bases do what?

A

they completely dissociate/ionise in water

49
Q

weak acids and bases do what?

A

they only partially dissociate/ionise in water

50
Q

10molL^-1 HCl = a _________ of a __________ acid
fill in the gaps

A
  • concentrated solution
  • strong
51
Q

what is acid deposition

A

how to put acid in an environment

52
Q

what are some causes of acid deposition

A
  • wet acid deposition
    • rain
    • snow
    • sleet
    • hail
    • fog
    • mist
    • dew
      all fall to the ground as aqueous precipitates
  • dry acid deposition
    • acidifying particles
    • gases fall to ground as dust, smoke
      these later dissolve in water to form acids
53
Q

what is the pH of normal rain

A

5.6 (rain is naturally acidic)

54
Q

what counts as acid rain?

A

any rain that has pH below 5.6 (normal rain)

55
Q

what are the primary pollutants to acid rain

A

oxides of sulphur and nitrogen

56
Q

is acid rain a primary or secondary pollutant

A

secondary as it is produced when acidic gases (oxides of sulphur and nitrogen) are dissolved in water

57
Q

how is sulfur dioxide produced

A

burning fossil fuels

produces H2SO3 or H2SO4 when dissolved in water, which are strong acids

58
Q

how is nitrogen oxides produced

A

internal combustion engines

produces HNO3 and HNO2 when dissolved in water which are strong acids

59
Q

what are the effects on acid deposition

A
  • impact on materials
  • impact on plant life
  • impact on water
  • impact on human health
60
Q

how can we reduce SO2 emissions

A

pre-combustion methods:
- remove the sulfur present in coal or oil before combustion
- hydrodesulfuristion, catalytic process which removes sulphur from refined petroleum products by reacting it with hydrogen to for hydrogen sulphide: H2S
post-combustion methods:
- flue-gas desulfurisation, removes up to 90% of SO2 from flue gas before it is released into the atmosphere. uses wet slurry of CaO and CaCO3 which reacts with SO2 to form neutral product: CaSO4

61
Q

how can we reduce emissions that cause acid rain in general?

A

lower the demand for fossil fuels: use more efficient energy transfer systems, public transport, and switching to renewable energy sources are all ways of reducing emissions

62
Q

how can we reduce NOx emissions

A
  • catalytic convertor in vehicles, catalyst converts toxic emissions into relatively harmless products
  • lower temperature combustion, the formation of nitrogen monoxide is reduced at lower temperature
63
Q

what is a lewis acid

A

an electron pair acceptor (electrophile, electron-deficient)

64
Q

what is a lewis base

A

an electron pair donator (nucleophile, electron-rich)

65
Q

what is a dative covalent bond

A

where one atom donates both electrons to the bond

66
Q

what bonds are lewis acid-base reactions

A

covalent, which will always be dative

67
Q

are all bronsted-lowry acids lewis acids or are all lewis acids bronsted-lowry acids

A

all bronsted-lowry acids lewis acids but not all lewis acids are bronsted-lowry acids

68
Q

pH =

A

– log [H30+]

69
Q

[H3O+] =

A

10^-Ph

70
Q

pOH =

A

– log [OH–]

71
Q

[OH–] =

A

10^-pOH

72
Q

pH + pOH =

A

14

73
Q

pH + pOH =

A

pKw

74
Q

Kw = in terms of [H3O+] and [OH–]

A

[H3O+] [OH–] = 10^ (–14)

75
Q

Kw = in terms of Ka and Kb

A

Ka x Kb

76
Q

pKw = in terms of pH and pOH

A

pH + pOH = 14

77
Q

pKw = in terms of pKa and pKb

A

pKa + pKb

78
Q

do you include liquids in K expressions

A

nonononono

79
Q

the stronger the acid, the ________ the pKa value

A

lower

they are inversely propotional

80
Q

what assumptions are you making when calculating the pH of weak acids
eg. ants contain formic acid (HCOOH). At concentration of 0.01mol L^(-1), what is the pH of squashed ant? pKa = 3.75

A

[HCOO–] = [H3O+]
- ignore [H3O+] from water because this is negligible

[HCOOH] = 0.01 mol L^(–1)
- because hardly any of the HCOOH has reacted

81
Q

for weak acids, what does [H3O+] =

A

…___________
√ [acid/HA] x Ka

82
Q

what assumptions are you making when calculating the pH of weak acids
eg. the ammonia you wash windows with has a concentration of 0.1mol L^(–1). What is its pH? pKa(ammonium ion) = 9.24

A

[NH4+] = [OH–]
- ignore [OH–] from water because this is negligible

[NH3] = 0.1mol L^(–1)
- because hardly any of the NH3 has reacted

83
Q

what is the conjugate base of H2CO3

A

HCO3–

84
Q

what is the conjugate acid of HSO4–

A

H2SO4

85
Q

the stronger the acid (___ pKa), the weaker the conjugate base (____ pKb)

A

low pKa
high pKb

86
Q

the weaker the acid (____pKa), the stronger the conjugate base (___pKb)

A

high pKa
low pKb

87
Q

the stronger the base (____pKb ), the weaker the conjugate acid (___pKa)

A

high pKb
low pKa

88
Q

the weaker the base (____pKb), the stronger the conjugate acid (____pKa)

A

low pKb
high pKa

89
Q

what is the relationship between Ka and pKa

A

inverse, so high Ka means low pKa vice versa

90
Q

what is the relationship between Kb and pKb

A

inverse, so high Kb means low pKb vice versa

91
Q

what is the definition of a buffer

A

an aqueous solution consisting of a weak acid and its conjugate base (or a weak base and its conjugate acid) that resists changes to pH when small amounts of acid or base are added

92
Q

how do you make a buffer solution

A
  1. mixing roughly equal amounts of a weak acid and its conjugate base
    or
  2. partially neutralising a weak acid with a strong base, so that some of the weak acid remains and the rest has been converted to its conjugate base
93
Q

Strong acids produce n_______ a______

A

neutral anions
this refers to the ability of the species to react further
eg: HCl ––> Cl– + H+
=> will not react further

94
Q

strong bases produce n________ c_______

A

neutral cations
this refers to the ability of the species to react further
eg: NaOH ––> OH– + Na+
=> will not react further

95
Q

how do buffers keep the pH constant?

A

they react away any extra acid or base that is added to the solution by reacting them with a strong acid/base conjugate.

they are in an equilibrium reaction so it works according to Le Chatelier’s principle

96
Q

when does the equivalence point happen

A

when n(acid)=n(base)
on graph:
half-way up the point of inflection

97
Q

Why does the point of inflection happen

A

in most titrations, it is found that a big jump in pH occurs at the point of inflection

98
Q

Study the graphs in your booklet, pg 47

A
99
Q

what are indicators

A

they are very weak acids that have a different colour to their conjugate bases

100
Q

where is the buffer region in a graph

A

the flattish region of the titration curve (where the pH is hardly changing)

101
Q

at half way to the equivalence point, pH=

A

pH=pKa(weak acid)

102
Q

where does the equivalence point occur for a:
strong acid weak base

A

pH=7

103
Q

where does the equivalence point occur for a:
strong acid weak base

A

pH<7

104
Q

where does the equivalence point occur for a:
weak acid strong base

A

pH>7

105
Q

where does the equivalence point occur for a:
weak acid weak base

A

pH=7

106
Q

what is hydrolysis

A

it is a proton transfer

how to remember:
[H+] is also known as proton

107
Q

for every titration, there are at least two steps: Neutralisation and hydrolysis; explain these two steps

A
  1. neutralisation: eg.
    acid + base ––> salt + water
    - exist as ions in solution and will either do hydrolysis
  2. hydrolysis:
    proton transfer

Chemistry (5 decks)

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