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Chemistry Unit 2 How To Pass Book > Chemical Equilibrium > Flashcards

Chemical Equilibrium Flashcards

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1
Q

When is a reaction equilibrium

A

When the concentrations of reactants and products are constant

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2
Q

What’s the equilibrium constant

A

Has the symbol K

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3
Q

What does the value of the equilibrium constant give

A

Indicates the position of equilibrium

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4
Q

What does the numerical value of equilibrium constant depend on

A

The reaction temperature and is independent of concentration and/or pressure

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5
Q

What happens to K in endothermic reactions

A

A rise in temperature causes in increase in K and yield is increased

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6
Q

What happens to K in Exothermic reactions

A

A rise in temperature causes a decrease in K and yield of product is decreased

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7
Q

What does a catalyst do to equilibrium constant

A

Does not affect the value of the equilibrium constant

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8
Q

What’s dynamic equilibrium

A

Is when the rates of two opposing processes become equal

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9
Q

What’s a closed system

A

Has no exchange of matter or energy with its surroundings, must be the case for equilibrium to take place

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10
Q

In equilibrium what is the rate of the forward reaction equal to

A

The rate of the reverse reaction

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11
Q

What is le chateliers principle

A

If a system is at equilibrium and a change is made in any of the conditions then the system responds to counteract the change as much as possible

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12
Q

What does a catalyst do to equilibrium

A

Speeds up the rate at which equilibrium is achieve but has no effect on the position

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13
Q

What does increasing the concentration of reactants do

A

Moves equilibrium to the right

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14
Q

What does increasing concentration of products do

A

Moves equilibrium to the left

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15
Q

What does increasing temperature do

A

Equilibrium shifts direction to the endothermic side

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16
Q

What does decreasing temperature do

A

Equilibrium shifts to direction of Exothermic reaction

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17
Q

What’s the equilibrium constant formula

A

aA +bB - cC +dD k=[C]c[D]d/ [A]a[B]b

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18
Q

What’s homogeneous equilibrium

A

All the species are in the same gaseous phase

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19
Q

What’s heterogeneous equilibrium

A

The species are in more than one phase

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20
Q

What’s the value given to pure solids or liquids acting as solvents in equilibrium reaction

A

1

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21
Q

What are equilibrium constants independent of

A

Concentrations or partial pressures of species in any given reaction

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22
Q

What’s the ratio of reactants and products when there is a low and high value of K

A

High K-more product
Low K-more reactant

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23
Q

Where does equilibrium lie when k is bigger, less and equal to one

A

Bigger lies more to the right
Less lies more to the left
Equal favours neither reactants or products

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24
Q

What does knowing the value of constant allow us to do

A

-Determine the direction in which a reaction will proceed to achieve equilibrium
-The ratio of the concentrations of reactants and products when equilibrium is reached

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25
Q

What happens to K at high and low temperatures

A

At high temps products are favoured so K increases
At low temps reactants are favoured so K decreases

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26
Q

What does a catalyst do to equilibrium

A

Speeds up the rates of the forward and reverse reactions by an alternative reaction pathway with lower activation energy

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27
Q

What’s the Brønsted-Lowry definition

A

States that an acid is a proton donor and a base is a proton acceptor

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28
Q

What is there for every acid and base

A

For every acid there is a conjugate base formed by the loss of a proton
For every base there is a conjugate acid formed by the gain of a proton

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29
Q

In water and aqueous solutions what is there an equilibrium between

A

Water molecules and hydronium and hydroxide ions

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30
Q

What is the equation for the equilibrium in water and aqueous solutions

A

H2O(l) + H2O(l) <=> H3O+(aq) + OH-(aq)

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31
Q

How can water be described

A

As amphoteric and can act as an acid or base

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32
Q

What is Kw

A

The dissociation constant for the ionisation of water and known as the ionic product

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33
Q

What is the value of Kw

A

Varies with temperature and at 25 degrees it is 1x10 to the -14

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34
Q

What is the relationship between ph and hydrogen ion concentration given by

A

pH= -log10[H3O+]
And [H3O+]= 10 the the -ph

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35
Q

In water and aqueous solutions with a ph of 7 the conc of H3O+ and OH- is what

A

10 to the -7 at 25 degrees

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36
Q

How to calculate the concentration of the other ion if either H3O+ or OH- is known

A

Calculate Kw using
pH+pOH=14

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37
Q

What are hydronium ions

A

H+ ions

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38
Q

Describe an acid

A

Proton donor and when it donates the species left is called a conjugate base

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39
Q

Describe a base

A

Proton acceptor and when it accepts a proton the species formed is a conjugate acid

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40
Q

What’s the ionic product

A

The dissociation constant for the ionisation of water, Kw

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41
Q

What is the Kw formula

A

Kw=[H3O+(aq)][OH-(aq)]

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42
Q

What is the ph scale

A

Gives a measure of the concentration of hydrogen ions in am aqueous solution

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43
Q

How can the ph of any aqueous solution be calculated

A

pH= -log10[H3O+] and [H3O+] = 10 to the -pH

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44
Q

What is the ph scale and what does it mean

A

A logarithmic scale meaning any change in pH unit requires a factor of 10 change in the hydrogen ion concentration

45
Q

What do strong acids and bases do

A

Fully dissociate in water to ions

46
Q

What do weak acids and bases do

A

Only dissociate partially in water to ions

47
Q

What are examples of strong acids and bases

A

Acids- nitric, sulfuric and hydrochloric acid
Base-sodium and potassium hydroxide

48
Q

What are examples of weak acid and bases

A

Acids- ethanoic, carbonic and sulfurous acid
Base- ammonia and amines

49
Q

What’s the formula for finding the pH of strong acids and bases

A

pH＝-log10[H＋]

50
Q

What’s a monoprotic or mono basic acid

A

Any weak or strong acid which is capable of donating only one hydrogen ion per molecule

51
Q

What’s a diprotic or dibasic acid

A

An acid hitch can donate two hydrogen ions per molecule

52
Q

What is the degree of ionisation definition

A

The ability of the non-ionised acid molecule to produce hydrogen ions

53
Q

When do acids tend to be stronger

A

The more the acid can produce hydrogen ions.
Tend to be lab acids
They fully dissociate in water meaning there is a one way arrow in the equation

54
Q

What happens when water is added to an acid

A

Strength is not related to the concentration of the acid. More water will produce a more dilute acid but will not alter the strength of the acid

55
Q

Where do you find weak acids

A

In equilibrium mixtures of non ionised acid molecules, hydrogen ions and the conjugate base of the acid

56
Q

What are examples of weak acids

A

Most carboxylic acids, ethanoic acid

57
Q

Describe ethanoic acid

A

The acidic hydrogen atom is the one bonding to the oxygen atom, only some of the ethanoic acid molecules dissociate into ions, it’s a weak monoprotic acid

58
Q

What is classified as a base

A

Any substance that reacts with an acid and accepts the proton from the acid

59
Q

What is a soluble base called

A

Alkali as it will produce hydroxide ions when in an aqueous solution

60
Q

What is the rule between alkali and bases

A

All alkalis are bases but not all bases are alkali

61
Q

What is a strong base and examples

A

A string base dissociates completely in aqueous solution. Strong bases are typically group 1 metal hydroxides e.g sodium hydroxide

62
Q

What are weak bases and examples

A

Weak bases only partially dissociate in aqueous solutions. Ammonia and amino alkanes are examples

63
Q

How do you tell the difference between weak and strong acid and bases by an equation

A

Weak have equilibrium arrow (two)
Strong only have one arrow in the equation

64
Q

For acids and bases that ionise fully what can be determined

A

The H+ or OH- can be determined from the initial concentration of the acid or base

65
Q

What’s the formula for strong acids

A

PH= -log10[H+]
[H+]=10 to the -ph

66
Q

What’s the formula for strong bases

A

Kw=[H+][OH-]

67
Q

What’s the acid dissociation constant formula

A

Ka= [products]/[reactants]=[H+][A-]/[HA] or by pKa=-log10Ka

68
Q

How is the approximate pH of a weak acid found

A

pH= 1/2pKa - 1/2log10c

69
Q

Describe equimolar solutions of weak and strong acids or bases

A

Have different pH values, conductivity and reaction rates, but the stoichiometry of reactions are the same

70
Q

How is a neutral solution formed from a soluble salt

A

A soluble salt of a strong parent acid or strong parent base dissolves in water

71
Q

How is an alkaline solution formed from a soluble salt

A

A soluble salt of a weak parent acid a strong parent base dissolves in water

72
Q

How is an acidic solution formed from a soluble salt

A

A soluble salt of a strong parent acid and a weak parent base dissolves in water to produce an acidic solution

73
Q

What is the equation formula for acid dissociation constant

A

HA(aq) equilibrium arrows H3O+ (aq) + A- (aq) use this to put into the formula Ka=[H+][A-]/ [HA]

74
Q

What is the symbol c in acid dissociation constant

A

The original acid concentration which is [HA]

75
Q

Describe ammonia

A

Weak base and is polar covalent gas molecule that dissolves readily in water a small amount of its molecules reacts with water to produce hydroxide ions

76
Q

What happens the weaker the base is

A

The weaker the base is the stronger the conjugate acid that will be formed with a higher Ka value in other words the conjugate acid of a weak base is a strong acid

77
Q

What do strong acids with greater dissociation have

A

Greater concentration of hydrogen ions and so have a lower ph and Greater conductivity

78
Q

Compare weak and strong bases

A

Weak bases produce fewer OH- ions and therefore less alkaline than strong bases of equal concentration. Weak bases have a lower ph and therefore conductivity

79
Q

What does the pH of a salt solution depend on

A

The strength of the parent acid and parent base from which it was formed

80
Q

What are all salts

A

All salts are strong electrolytes and dissociate completely in solution

81
Q

What is the ph of a solution of a salt of a weak acid and a strong base

A

Ph greater than 7

82
Q

What is the ph of a solution of a salt of a strong acid and weak base

A

Ph less than 7

83
Q

What is a buffer solution

A

A buffer solution is one in which the pH remains approximately constant when small amounts of acid or base are added

84
Q

What does an acid buffer consist of

A

Consists of a solution of a weak acid and one of its salts

85
Q

What does a basic buffer consist of

A

Consists of a solution of a weak base and one of it’s salts

86
Q

How can the required composition of an acid buffer solution be calculated

A

From the desired ph and the acid dissociation constant

87
Q

What’s the formula for calculating the approximate ph of an acid buffer solution

A

pH= pKa-log10 x [acid]/[salt]

88
Q

What are indicators

A

Weak acids and represented as Hln (aq) + H2O (l) ea H3O+ (aq) + ln- (aq)

89
Q

In an aqueous solution what is the colour of the acid

A

The colour of the acid is distinctly different from that of it’s conjugate base

90
Q

How is the colour of an indicator determined

A

The ratio of [Hln] to [ln-]

91
Q

What is the theoretical point at which colour change occurs

A

[H3O+]=Kln

92
Q

When is colour change distinguishable

A

When [Hln] and [ln-] differ by a factor of 10

93
Q

What’s the pH range over which colour change occurs

A

Estimated by pH=pKln + or - 1

94
Q

How are buffer solutions defined

A

As solutions that resist the change in pH, remain constant on adding small amounts of acid or base or by diluting the solution with water

95
Q

What are uses if bufffers

A

Skin creams

96
Q

What are the two types of buffers

A

Acid buffers and basic buffers

97
Q

What’s an acid buffer

A

The solution contains a mixture of weak acid and its conjugate base the ph is lower than 7

98
Q

Whats a basic buffer

A

A solution that contains a mixture of a weak base and its conjugate acid the ph id higher than 7

99
Q

What equation represents a buffer

A

The equilibrium equation, HA ea H+ = A-
HA is the acid
H+ is the conjugate acid
A- is the conjugate base

100
Q

What must a buffer do to stabilise the ph of a solution

A

Must be able to react with added OH and H ions

101
Q

Learn how to do all k calculations

A
102
Q

What are indicators

A

Are weak acids or bases that are able to give a measure of the pH of a solution by their colour represented as Hln (aq) + H2O+ ea H3O+ + Ln- (aq)

103
Q

What must be considered when deciding which indicator to use in a trait ration

A

The equivalence point

104
Q

What is the equivalence point

A

Is the point in a titration where the amount of titration added is enough to neutralise the analyse solution completely

105
Q

What indicates the type of titration

A

The shape of the curve, the vertical region of the curve shows where there is a rapid change in ph and shows the equivalent point

106
Q

How do you figure out a suitable indicator

A

For a strong acid strong base titration between ph 3 to 10
Weak acid strong base ph 7 to 10
Strong acid weak base ph 3 to 8
Weak acid weak base need a ph meter to produce a titration curve

107
Q

What does the equivalence point depend on

A

The strength of the acid and base used and the nature of the alt formed at the end point

108
Q

What does the indicator colour during a titration depend on

A

The concentration of non ionised indicator molecules [Hln] and the conjugate base molecules [ln-]

109
Q

What indicator is suitable for a weak acid weak base titration

A

No suitable indicator

Chemistry Unit 2 How To Pass Book (3 decks)

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