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Advanced Higher Chemistry > Unit 1 Inorganic Chemistry: Key Area 4 - Chemical Equilibrium > Flashcards

Unit 1 Inorganic Chemistry: Key Area 4 - Chemical Equilibrium Flashcards

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1
Q

what are the 3 factors that affect equilibrium?

A

1) Concentration
2) Temperature
3) Pressure (only applies to gaseous substances)

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2
Q

In the reaction A + B ⇌ C + D what happens to equilibrium if you add more A or B (reactant)?

A

Shifts to right

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3
Q

In the reaction A + B ⇌ C + D what happens to equilibrium if you remove more C or D (product)?

A

Shifts to right

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4
Q

In the reaction A + B ⇌ C + D what happens to equilibrium if you add C or D (product)?

A

Shifts to left

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5
Q

In the reaction A + B ⇌ C + D what happens to equilibrium if you remove A or B (reactant

A

Shifts to left

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6
Q

In the reaction A + B ⇌ C + D ΔH = -ve what happens to equilibrium if you increase temperature?

A

Favours the endothermic reaction.

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7
Q

In the reaction A + B ⇌ C + D ΔH = -ve what happens to equilibrium if you decrease temperature?

A

Favours the exothermic reaction.

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8
Q

In the reaction A(g) + B(g) ⇌ C(g) + D(g) what happens to equilibrium if you increase pressure?

A

Shift to side which has less gaseous moles.

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9
Q

In the reaction A(g) + B(g) ⇌ C(g) + D(g) what happens to equilibrium if you decrease pressure?

A

Shift to side with more gaseous moles.

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10
Q

What are the 2 types of equilibrium?

A

Homogeneous and Hetrogeneous.

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11
Q

What happens in Homogeneous equilibrium?

A

Reactants and products are in the same physical state.

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12
Q

What happens in Hetrogeneous equilibrium?

A

Reactants and products are in different physical states.

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13
Q

What does the value of an equilibrium constant indicate?

A

The position of equilibrium.

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14
Q

What are factors that affect equilibrium constant?

A

K is dependent on temperature and independent of concentration and pressure.

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15
Q

In the reaction A + B ⇌ C + D ΔH = -ve how does a rise in temperature affect K?

A

It will shift the equilibrium to the left, decreasing the quantity of products and increasing the quantity of reactants. Which will cause a decrease in K.

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16
Q

In the reaction A + B ⇌ C + D ΔH = +ve how does a rise in temperature affect K?

A

It will shift the equilibrium to the right, increasing the quantity of products and decreasing the quantity of reactants. Which will cause an increase in K.

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17
Q

How does concentration affect the equilibrium position and the value of K?

A

Equilibrium position - Changes

Value of K - No Change

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18
Q

How does temperature affect the equilibrium position and the value of K?

A

Equilibrium position - Changes

Value of K - Changes

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19
Q

How does pressure affect the equilibrium position and the value of K?

A

Equilibrium position - Changes

Value of K - No Change

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20
Q

How does catalyst affect the equilibrium position and the value of K?

A

Equilibrium position - No Change

Value of K - No Change

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21
Q

What are liquids that do not mix said to be?

A

Immiscible

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22
Q

What does dissolving a solute in 2 immiscible liquids allow the solute to do?

A

Distribute itself between the 2 liquids.

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23
Q

What is a H+ ion?

A

Proton

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24
Q

What happens to the H+ ion in water?

A

As it cannot exist on its own, it is attracted to the polar water molecules. It becomes a hydrated proton known as a hydronium ion (H3O+) and the H+ ion and water molecule form a dative covalent bond.

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25
Q

How can the ionisation of water be represented?

A

H2O(l) H2O(l) ⇌ H3O+(aq) + OH−(aq)

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26
Q

What is a hydronium atom?

A

A hydrated proton H3O+(aq).

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27
Q

What is a shortened version of H3O+(aq)?

A

H+

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28
Q

What is the K value of pure water?

A

1

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29
Q

As pure water has a value of K what is the equation of K for pure water?

A

K = [H3O+] [OH−] or K = [H+] [OH−]

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30
Q

What is the equilibrium constant Kw known as?

A

The ionic product of water.

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31
Q

What is water in terms of K and what does this mean?

A

Water is amphoteric meaning it can act as both an acid and a base.

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32
Q

At 25°C what is the approximate value of K?

A

1x10(14)

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33
Q

How do higher temperatures affect the pH of water?

A

They do not become more acidic.

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34
Q

In water and aqueous solutions with a pH value of 7 and temperature of 25°C what are the concentrations of H3O+(aq) and OH−(aq)?

A

Both x 10(-7) mol/l.

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35
Q

If the concentration of H3O+(aq) or the concentration of

OH−(aq) is known, how can the concentration of the other ion can be calculated?

A

Using Kw or by usH + pOH = 14.

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36
Q

When is a solution said to be acidic?

A

When there is an excess of hydrogen ions over hydroxide ions (i.e. pH < pOH).

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37
Q

In the case of water what is the concentration of always the same?

A

The concentration of hydrogen ions and hydroxide ions.

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38
Q

What still stays the same in water even if the pH of the water changes?

A

The water stays neutral (pH =pOH).

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39
Q

What type of scale is a pH scale?

A

A logarithmic scale

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40
Q

What does a change in pH by 1 unit change the concentration of H+ by?

A

10

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41
Q

What does a change in pH by 2 units change the concentration of H+ by?

A

100

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42
Q

What is the value of pH +pOH?

A

14

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43
Q

What does the Arrhenius definition of acids and bases only apply to?

A

Aqueous solutions

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44
Q

What is the Arrhenius definition of what happens to an acid when it is dissolved in water?

A

An acid dissociates to increase H+ ions when dissolved in water e.g. [H+] > [OH-]. (Acids produce H+ ions in aqueous solution).

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45
Q

What is the Arrhenius definition of what happens to a base when it is dissolved in water?

A

A base dissociates to increase OH- ions when dissolved in water e.g. [OH-] > [H+]. (Bases produce OH− ions in aqueous solution).

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46
Q

What are problems with the Arrhenius definition of how acids and bases dissolve in water?

A
  • Why substances, such as NH3 and Na2CO3, dissolve in water to form basic solutions, even though they do not contain OH– ions.
  • Why substances, such as CO2, dissolve in water to form acidic solutions, even though they do not contain H+ ions.
  • That acid–base reactions take place outside aqueous solution.
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47
Q

What is the Brønsted Lowry definition of acids and bases?

A

The Brønsted-Lowry definitions of acids and bases state that an acid is a proton donor and a base is a proton acceptor. (does not need to have OH-) Base structure must contain an atom with an unshared pair of electrons.

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48
Q

For the equation HCL(aq) + H2O(l) ⇌ H3O+(aq) +Cl-(aq) what happens according to the Brønsted Lowry theory?

A
  • HCL donates a proton to water therefore HCL is an acid.

- H2O accepts a proton from HCL therefore H2O is a base.

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49
Q

What happens in a Brønsted Lowry acid-base reaction?

A
  • The original base becomes an acid in the reverse reaction.

- The original acid becomes a base in the reverse process.

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50
Q

For every acid what is there?

A

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

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51
Q

What is the general equation for a conjugate acid reaction?

A

HA (acid) ⇌ H+ + A-(conjugate base)

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52
Q

What is the general equation for a conjugate acid reaction H2O(l) + H2O(l) ⇌ H3O+(aq) + OH-(aq)?

A

H2O(l)(acid) + H2O(l) ⇌ H3O+(aq) + OH-(aq)(conjugate base)

53
Q

What is the general equation for a conjugate acid reaction of HCL(aq) + H20(l) ⇌ H30+(aq) + Cl-(aq)?

A

HCL(aq)(acid) + H20(l) ⇌ H30+(aq) + Cl-(aq)(conjugate base)

54
Q

For every base what is there?

A

A conjugate acid which is formed by the gain of a proton.

55
Q

What is the general equation for a conjugate base reaction of NH3 + H2O ⇌ NH4+ + OH-?

A

NH3(base) + H2O ⇌ NH4+(conjugate acid) + OH-

56
Q

What is the general equation for a conjugate acid reaction of CO3^2-(aq) + H3O+(aq) ⇌ HCO3^-(aq) +H2O(l)?

A

CO3^2-(aq)(base) + H3O+(aq) ⇌ HCO3^-(aq) +H2O(l)(conjugate acid)

57
Q

What is the general equation for a conjugate acid and base reaction of OH+(aq) + H3O+ (aq) ⇌ H2O(l) + H2O(l)?

A

OH+(aq)(base) + H3O+(aq)(acid) ⇌ H2O(l)(conjugate acid) + H2O(l)(conjugate base)

58
Q

What do conjugate acid-base pairs differ by?

A

Only one proton

59
Q

What can amphoteric substances act as?

A

Either an acid or a base because they have both a transferable H and an atom with lone pair electrons. As water can act as a base, accepting H+ from HCL and as an acid by donating H+ to NH3.

60
Q

What are acids either?

A

Acids are either strong or weak depending on wether or how they (dissociate) dissolve in water.

61
Q

How do strong acids dissociate into ions in solution?

A

Strong acids are completely dissociated into ions in aqueous solution.

62
Q

What is an example of a strong acid reaction and what would be the [H+] concentration if the HCL concentration is 0.1 mol/l?

A

HCL(aq) + H20(l) ⇌ H30+(aq) + Cl-(aq)

[H+] concentration is 0.1 mol/l

63
Q

What are examples of strong acids?

A
  • Hydrochloric acid (HCL)
  • Nitric acid (HNO3)
  • Sulphuric acid (H2SO4)
64
Q

How do weak acids dissociate into ions in solution?

A

Weak acids do not completely dissociate into ions in solution.

65
Q

What is an example of a weak acid reaction and why is this?

A

CH3COOH(aq) ⇌ CH3COO-(aq) + H20+(aq)

- Ethanoic acid solutions contain molecules of CH3COOH as well as H3O+ and CH3COO- ions.

66
Q

What are examples of weak acids and where can more examples be found?

A
  • Ethanoic acid (CH3COOH)
  • Methanoic acid (HCOOH)
  • Sulphurous acid (H2SO3)
  • Carbonic acid (H2CO3)
  • Pg 13 in the databook
67
Q

What does the type of solvent effect?

A

The acid properties

68
Q

What is an example of a solvent that affects acidic properties?

A

HCL in non - polar solvents - no dissociation therefore only HCL molecules no ions, so it is not an acid.

69
Q

How do strong bases/alkalis dissolve?

A

By completely dissociating into ions.

70
Q

How do weak bases/alkalis?

A

Do not completely dissociate into ions in solution.

71
Q

Strong acid vs weak acid?

A

Higher conductivity, lower pH, faster reaction due to higher H+ ion concentration.

72
Q

Strong base/alkali vs weak base/alkali?

A

Higher conductivity, higher pH due to higher OH- ion concentration.

73
Q

What do equimolar solutions of strong and weak acdis and alaklis differ in?

A

Concentration, pH and speed of reaction. This is due to the different concentration of H+ and OH- ions in solution.

74
Q

How do strong bases/alkalis dissolve?

A

By completely dissociating into ions.

75
Q

What is an example of a strong base/alkali reaction?

A

NaOH(s) + (aq) ⇌ Na+(aq) + OH-(aq)

76
Q

What are examples of strong base/alkalis?

A
  • Sodium hydroxide (NaOH)
  • Potassium hydroxide (KOH)
  • Lithium hydroxide (LiOH)
77
Q

How do weak bases/alaklis dissolve?

A

They do not completely dissociate into ions in solution.

78
Q

What is an example of a weak base/alkali reaction and why?

A

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

Ammonia solutions contain molecules of NH3 as well as NH4+ and OH- ions.

79
Q

What are examples of weak bases /alkalis

A
  • Aminomethane (CH3NH2)
  • Ammonia (NH3)
  • Aminoethane (C2H5NH2)
80
Q

what does the pH of a salt solution depend on?

A

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

81
Q

What is the pH of a salt of a strong acid and weak base?

A

Acidic

82
Q

What is the pH of a salt of a strong acid and strong base?

A

Neutral

83
Q

What is the pH of a salt of a strong acid and weak base?

A

Alkaline

84
Q

What are all salts?

A

All salts are strong electrolytes and completely ionise in solution.

85
Q

What will happen to the ions of a weak acid or base when dissolved?

A

They will set up an equilibrium with the ions in water.

86
Q

What happens in terms of equilibrium in the acidic salt reaction of Ammonium chloride with water?

A

Ammonium chloride completely dissociates. The ammonium ions form an equilibrium with the OH- ions moving the water equilibrium to the right. Excess H+ are formed so pH is less than 7.

87
Q

What happens in terms of equilibrium in the alkaline salt reaction of Sodium Ethanoate with water?

A

Sodium ethanoate completely dissociates. The ethanoate ions form an equilibrium with the H+ ions moving the water equilibrium to the right. Excess OH- ions are formed so the pH is greater than 7.

88
Q

What is a soap?

A

Soap is a salt formed between a fatty acid (weak acid) and sodium or potassium hydroxide. Therefore soaps are alkaline.

89
Q

When a weak acid is dissolved in water what is the general dissociation?

A

HA ⇌ H+ + A-

90
Q

What is Ka known as?

A

The acid dissociation constant.

91
Q

What is the equation for the acid dissociation?

A

Ka = ([H3O+] [A-]) / [HA] or pKa = -log10 Ka

92
Q

What does a smaller value of Ka represent?

A

A weaker acid

93
Q

When is the equation for amending Ka to find out [H+] of the dissociation of a weak acid?

A

H+ = √Ka x C where C is the concentration of the acid.

94
Q

What does pKa represent?

A

The dissociation constant of an acid.

95
Q

How can the value of pKa be found?

A

pKa = -log10 Ka

96
Q

Where are the Ka values found?

A

Pg 13 on the data book

97
Q

What does an increase in Ka represent and how does this affect the value of pKa?

A

As Ka increases (acid strength increases) and pKa decreases (due to the pKa equation above).

98
Q

What is the equation for the pH value of a weak acid?

A

pH = 1/2 pKa - 1/2 log10c

99
Q

What is the equation for diluting an acid?

A

pH = -log10 [H+]

100
Q

What is the pH of 0.1 mol l-1 of a strong acid?

A

pH = -log10(0.1) = 1

101
Q

What is the pH of 0.01 mol l-1 of a strong acid?

A

pH = -log10(0.01) = 2

102
Q

How will a dilution of a strong acid by a factor of 10 affect the pH of the acid?

A

Change the pH of the acid by 1 unit.

103
Q

What is the pH of 0.1 mol l-1 of a weak acid?

A

pH = 1/2 pKa - 1/2 log(0.1) = 0.5

104
Q

What is the pH of 0.01 mol l-1 of a weak acid?

A

pH = 1/2 pKa - 1/2 log(0.01) = 0.

105
Q

How will a dilution of a strong acid by a factor of 10 affect the pH of the acid?

A

Change the pH of the acid by 0.5 units.

106
Q

What is a buffer solution?

A

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

107
Q

What are the 2 types of buffers?

A

Basic and acidic

108
Q

What are common examples of buffers?

A

Blood, Swimming pool, Contact lens solution.

109
Q

What does an acid buffer consist of?

A

An acid buffer consists of a solution of a WEAK acid and one of its SALTS.

110
Q

What can a weak acid supply to an acid buffer?

A

The weak acid can supply additional hydrogen ions when these are removed by the addition of a small amount of base.

111
Q

What can the salt of a weak acid provide to an acid buffer?

A

The salt of the weak acid provides the conjugate base, which can absorb excess hydrogen ions produced by the addition of small amounts of acid.

112
Q

What does a basic buffer consist of?

A

A solution of a weak base and one of its salts.

113
Q

What does a weak base provide in a basic buffer?

A

Remove excess added hydrogen ions.

114
Q

What does the salt of the base provide in a basic buffer?

A

The conjugate acid to replace hydrogen ions removed.

115
Q

What is the equation for the pH of a buffer solution?

A

pH = pKa - log10[acid/salt]

116
Q

What are indicators?

A

Indicators are weak acids that change colour when they are converted into their conjugate base.

117
Q

How can the dissociation of indicators be represented and what is the calculation for the dissociation constant for the indicator?

A

Hln(aq) + H2O(l) ⇌ H3O+(aq) + ln-(aq)

Kln = ([H3O+] [ln-]) / [Hln]

Where :
In- = indicator

Hln = conjugate base

And In- and HIn have different colours

118
Q

In an aqueous solution what is distinctively different between the acid indicator and that of its conjugate base?

A

Colour

119
Q

What is the colour of an indicator determined by?

A

The colour of the indicator is determined by the ratio of [HIn] to [In-].

120
Q

What is the theoretical point at which a colour change occurs in an indicator?

A

The theoretical point at which colour change occurs is when [H3O+] = KIn.

121
Q

When is the colour change said to be distinguishable in an indicator?

A

when [HIn] and [In-] differ by a factor of 10.

122
Q

How can the pH range over which a colour change occurs be estimated by the expression:
pHpKIn 1

A

pH = pKIn (+/-) 1

123
Q

What is the equivalence point?

A

When the reaction is just completed.

124
Q

For a titration between a strong acid and a strong base what will the equivalence point be?

A

pH 7

125
Q

If titrating with a base, what should you ideally choose the indicator to be?

A

An indicator that has a pKIn 1 less than the pH at the equivalence point.

126
Q

If titrating with an acid, what should you ideally choose the indicator to be?

A

An indicator that has a pKIn 1 more than the pH at the equivalence point.

127
Q

What will the equivalence point be for a weaker acid?

A

Higher as the change in pH becomes less dramatic.

128
Q

What does the pH have to be at least for the indicator to work?

A

2

Advanced Higher Chemistry (6 decks)

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