ATAR Unit 3 (1) Flashcards

1
Q

open system

A

exchanges energy & matter w. surroundings

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2
Q

closed system

A

exchanges only energy w. surroundings

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3
Q

reversible reaction

A

reaction where the products once formed can react together to re-form the reactants

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4
Q

reversibility [chemical]

A

only some chemical changes are reversible

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5
Q

reversibility [physical]

A

physical changes are usually reversible

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6
Q

four common reversible systems

A

evaporation & condensation of water [physical]

saturated sugar / salt solution [physical]

oxygen transport in blood [physical]

synthesis of ammonia [chemical]

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7
Q

static equilibrium

A

position of balance is achieved but no processes are happening [e.g. seesaw]

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8
Q

dynamic equilibrium

A

equal rate of forward & reverse reactions is achieved in closed systems

macroscopic properties remain constant & microscopic processes continue

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9
Q

reversibility [considering activation energy]

A

reactants collide w. sufficient energy [Eₐ] to form products

products collide w. sufficient energy [reverse Eₐ] to form reactants

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10
Q

extent of reaction

A

indicates how much product is formed at equilibrium

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11
Q

rate of reaction

A

measures the change in reactants & products w. time

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12
Q

graphing rate vs time

A

shape of the graph [rate theory]

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13
Q

graphing concentration vs time

A

stoichiometry of the reaction [coefficient]

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14
Q

le chatalier’s principle

A

if stress is applied to a system at equilibrium, the system will act to oppose the stress & restore equilibrium

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15
Q

increase temperature [exothermic reaction]

A

endothermic reaction absorbs heat

reverse reaction is favoured

moves to left-hand-side

reactants are favoured

K𝒸 decreases

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16
Q

decrease temperature [exothermic reaction]

A

exothermic reaction releases heat

forward reaction is favoured

moves to right-hand-side

products are favoured

K𝒸 increases

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17
Q

increase temperature [endothermic reaction]

A

endothermic reaction absorbs heat

forward reaction is favoured

moves to right-hand-side

products are favoured

K𝒸 increases

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18
Q

decrease temperature [endothermic reaction]

A

exothermic reaction releases heat

reverse reaction is favoured

moves to left-hand-side

reactants are favoured

K𝒸 decreases

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19
Q

increasing temperature effect [collision theory]

A

more kinetic energy within reactants & products

molecules move faster

more successful collisions

greater rate of reaction

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20
Q

pressure’s effect on K𝒸

A

changing pressure has no effect on the K𝒸 value

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21
Q

what if the number of molecules is equal on both sides of the chemical equation [2 : 2 molecules equation] ? [pressure]

A

change in pressure will not shift the position of equilibrium [no effect]

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22
Q

volume’s effect on pressure

A

if volume is doubled, pressure is halved

if volume is halved, pressure is doubled

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23
Q

increase pressure [3 : 2 molecules equation]

A

moves to the side of fewest molecules

net forward reaction

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24
Q

decrease pressure [3 : 2 molecules equation]

A

moves to the side of more molecules

net reverse reaction

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25
Q

increasing pressure effect [collision theory]

A

reduced volume equals increased pressure

molecules are closer together

increased frequency of collisions

greater rate of reaction

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26
Q

increase reactant

A

formation of more products

position of equilibrium shifts right

net forward reaction

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27
Q

increase product

A

formation of more reactants

position of equilibrium shifts left

net reverse reaction

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28
Q

decrease reactant

A

formation of more reactants

position of equilibrium shifts left

net reverse reaction

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29
Q

decrease product

A

formation of more products

position of equilibrium shifts right

net forward reaction

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30
Q

inert gas’ effect on K𝒸

A

adding an inert gas has no effect on the K𝒸 value

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31
Q

concentration’s effect on K𝒸

A

changing concentration has no effect on the K𝒸 value

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32
Q

increase dilution

A

moves to the side of more molecules

equilibrium is restored

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33
Q

catalyst’s effect on K𝒸

A

a catalyst has no effect on the K𝒸 value

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34
Q

homogenous system

A

reactants & products are in the same phase

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35
Q

heterogeneous system

A

reactants & products are in different phases

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36
Q

K𝒸 expression

A

products to the power of their coefficient[s] divided by reactants to the power of their coefficient[s]

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37
Q

what species do & do not appear in a K𝒸 expression ?

A

solids & liquids do not appear

aqueous & gases do appear

liquids do appear [if all species in the reaction are liquid]

liquids do appear [if H₂O is a reactant / product]

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38
Q

Q𝒸 > K𝒸

A

moves to left-hand-side

more reactants

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39
Q

Q𝒸 < K𝒸

A

moves to right-hand-side

more products

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40
Q

10⁻⁴ < K𝒸 < 10⁴

A

extent of reaction is significant

reactants = products [at equilibrium]

41
Q

K𝒸 > 10⁴

A

extent of reaction is complete

products > reactants [at equilibrium]

equilibrium lies to the right-hand-side

42
Q

K𝒸 < 10⁻⁴

A

extent of reaction is negligible

reactants > products [at equilibrium]

equilibrium lies to the left-hand-side

43
Q

reversed equation’s effect on K𝒸

A

K𝒸 is inversed

44
Q

doubled equation’s effect on K𝒸

A

K𝒸 is squared

45
Q

halved equation’s effect on K𝒸

A

K𝒸 is square-rooted

46
Q

acid [arrhenius model]

A

substance that produces hydrogen ions [H⁺] in an aqueous solution [e.g. HCl]

47
Q

base [arrhenius model]

A

substance that produces hydroxide ions [OH⁻] in an aqueous solution [e.g. NaOH]

48
Q

neutralization reaction [arrhenius model]

A

reaction where hydrogen ions react w. hydroxide ions to form water [e.g. H₂O ⇌ H⁺ + OH⁻]

49
Q

acid + base →

A

salt + water [e.g. HCl + NaOH → NaCl + H₂O]

50
Q

acid + metal →

A

salt + hydrogen gas [e.g. 2HCl + Mg → MgCl₂ + H₂]

51
Q

acid + carbonate →

A

salt + water + carbon dioxide gas [e.g. HCl + CaCO₃ → CaCl₂ + H₂O + CO₂

52
Q

acid [brønsted–lowry model]

A

proton [H⁺] donor [e.g. HSO₄⁻]

53
Q

base [brønsted–lowry model]

A

proton [H⁺] acceptor [e.g. NH₃]

54
Q

neutralization reaction [brønsted–lowry model]

A

reaction where an acid reacts w. a base [e.g. NH₃ + H₂O ⇌ NH₄⁺ + OH⁻]

55
Q

conjugate acid-base pair

A

two species that differ by one proton [H⁺] [e.g. HNO₃ & NO₃⁻]

56
Q

conjugate acid

A

when a base accepts a proton [H⁺]

57
Q

conjugate base

A

when an acid donates a proton [H⁺]

58
Q

amphiprotic substances

A

can act as either acids or bases; can either donate or accept protons [e.g. H₂O]

59
Q

monoprotic acid

A

can donate one proton [e.g. HCl]

60
Q

diprotic acid

A

can donate two protons [e.g. H₂SO₄]

61
Q

triprotic acid

A

can donate three protons [e.g. H₃PO₄]

62
Q

polyprotic acid

A

can donate more than one proton to a base

63
Q

extent of dissociation [polyprotic acids]

A

first dissociation is greater than each subsequent dissociation; final dissociation occurs to the least extent; subsequent acids become progressively weaker

64
Q

strong acid

A

dissociates completely in aqueous solution; readily donates protons [e.g. HCl, H₂SO₄, HNO₃]

65
Q

weak acid

A

dissociates partially in aqueous solution; high proportion of undissociated acid particles [e.g. CH₃COOH, H₂CO₃, H₃PO₄]

66
Q

strong base

A

dissociates completely in solution; readily accepts protons [e.g. NaOH]

67
Q

weak base

A

dissociates partially in solution; high proportion of undissociated base particles [e.g. NH₃]

68
Q

relative strength relationship of conjugate acid-base pairs

A

stronger the acid, weaker the conjugate base [if an acid readily donates a proton, its conjugate base does not readily accept it back]

stronger the base, weaker the conjugate acid [if a base readily accepts a proton, its conjugate acid does not readily donate it forward]

69
Q

strength vs concentration

A

strength [strong / weak] refers to the degree of dissociation [tendency to donate / accept protons] of an acid / base

concentration [concentrated / dilute] refers to the relative amount of solute in a given volume of solution

70
Q

water

A

very weak electrolyte & undergoes self-ionization to a very small extent

71
Q

K𝒸 define

A

equilibrium constant / point of balance that exists in a reaction

72
Q

Kᴡ define

A

ionic product / ionization constant of water

73
Q

Kᴡ expression

A

[H₃O⁺][OH⁻] = 1 x 10⁻¹⁴

74
Q

temperature’s effect on Kᴡ

A

increase temperature, increase Kᴡ

decrease temperature, decrease Kᴡ

75
Q

pH expression

A

-log[H₃O⁺]

76
Q

dilution’s effect on pH [strong acids & bases]

A

no effect on the number of moles [c₁V₁ = c₂V₂]

77
Q

dilution’s effect on pH [acid at 25ºC]

A

pH increases until close to 7

78
Q

dilution’s effect on pH [base at 25ºC]

A

pH decreases until close to 7

79
Q

buffer

A

solution that is conjugate in nature & resists changes in pH when small amounts of acid / bases are added

80
Q

general equation [buffer]

A

HA ⇌ H⁺ + A⁻

BOH ⇌ B⁺ + OH⁻

81
Q

buffer composition

A

weak acid & conjugate base

weak base & conjugate acid

82
Q

increase H⁺ to buffer [small amount]

A

H⁺ reacts w. A⁻

moves to left-hand-side [le chatalier’s principle]

more HA

[H⁺] remains relatively constant

pH does not change significantly

83
Q

increase H⁺ to buffer [large amount]

A

H⁺ reacts w. A⁻

moves to left-hand-side [le chatalier’s principle]

more HA

exhaustion of A⁻

[H⁺] soars

pH plummets

84
Q

increase OH⁻ to buffer [small amount]

A

OH⁻ reacts w. H⁺ [neutralization]

moves to right-hand-side [le chatalier’s principle]

more weak acid HA dissociates

[H⁺] remains relatively constant

pH does not change significantly

85
Q

increase OH⁻ to buffer [large amount]

A

OH⁻ reacts w. H⁺ [neutralization]

moves to right-hand-side [le chatalier’s principle]

more weak acid HA dissociates

exhaustion of HA

[H⁺] plummets

pH soars

86
Q

two solutions [buffer]

A

CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺

NH₃ + H₂O ⇌ NH₄⁺ + OH⁻ [inverse response]

87
Q

Kₐ define

A

acid dissociation constant

88
Q

larger Kₐ

A

greater extent of dissociation

more products

more [H⁺]

stronger the acid

89
Q

smaller Kₐ

A

lesser extent of dissociation

more reactants

less [H⁺]

weaker the acid

90
Q

Kₐ of polyprotic acids

A

first dissociation has a greater Kₐ than each subsequent dissociation; each following step, Kₐ decreases; it becomes increasingly harder to lose a proton as the acid species becomes increasingly negative

91
Q

acid-base indicator

A

weak acid / weak base where the conjugate acid form is one colour & the conjugate base form is another colour

92
Q

pH range [indicator]

A

related to the indicator’s dissociation constant

position of equilibrium changes depending on the solution’s pH

colour change occurs when pKₐ = pH

93
Q

equivalence point [neutralization reaction]

A

when the amount [number of moles] of acid & base are in stoichiometric ratio [equal]

94
Q

end point

A

when the indicator changes colour

corresponds closely w. the equivalence point

95
Q

transition point [indicator]

A

when concentration of the acid form & base form are equal

pH = pKₐ = -log[H⁺]

96
Q

equivalence point

A

when the amount [number of moles] between reactants are in stoichiometric ratio [equal]

97
Q

half equivalence point

A

when the amount [number of moles] between conjugate acid-base pair are in stoichiometric ratio [equal]

pH = pKₐ = -log[H⁺]

98
Q

useful relationships [pKᴡ]

A

pKᴡ = pH + pOH = 14

pKᴡ = pKₐ + pKᵦ = 14

99
Q

useful relationships [Kᴡ]

A

Kᴡ = [H₃O⁺][OH⁻] = 1 x 10⁻¹⁴

Kᴡ = Kₐ x Kᵦ = 1 x 10⁻¹⁴