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A Level Chemistry > Module 5: Chapter 20 - Acids, Bases, and pH > Flashcards

Module 5: Chapter 20 - Acids, Bases, and pH Flashcards

1
Q

What is the solubility of group 1 salts?

A

They are all soluble

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2
Q

What is the solubility of nitrates (NO₃⁻)?

A

They are all soluble

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3
Q

What is the solubility of Halides?

A

All soluble except silver halides

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4
Q

What is the solubility of group 2 sulfates?

A

Solubility decreases down the group

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5
Q

What is the solubility of group 2 hydroxides?

A

Solubility increases down the group

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6
Q

What is a Brønsted-Lowry acid?

A

A proton donor

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7
Q

What is a Brønsted-Lowry base?

A

A proton acceptor

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8
Q

What is a monobasic acid?

A

An acid containing 1 hydrogen ion that can be replaced per molecule, i.e hydrochloric acid

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9
Q

What is a dibasic acid?

A

An acid containing 2 hydrogen ions that can be replaced per molecule, i.e sulfuric acid

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10
Q

What is a tribasic acid?

A

An acid containing 3 hydrogen ions that can be replaced per molecule, i.e phosphoric acid

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11
Q

Which metals will react with hydrochloric acid in a redox reaction?

A

Any metals more reactive than hydrogen (i.e not platinum gold silver or copper)

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12
Q

What is a cojugate acid-base pair?

A

A set of 2 species that transform into each other by the gain or loss of a proton

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13
Q

Which species will have more basic properties, the conjugate base of a strong acid or the conjugate base of a weak acid?

A

As a strong acid completely dissociates, the reaction is not reversible so the conjugate base does not have any basic properties. However, a weak acid only partially dissociates so the reaction can be reversed and the conjugate base does have basic properties. Therefore, the conjugate base of a weak acid has stronger basic properties

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14
Q

Identify the conjugate pairs

A
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15
Q

Identify the conjugate pairs

A
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16
Q

Identify the conjugate pairs

A
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17
Q

What is the definition of pH?

A

pH = -log₁₀[H⁺]

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18
Q

What is the equation for pH?

A

pH = -log₁₀[H⁺]

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19
Q

How many decimal places do you give pH to?

A

Always to 2dp

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20
Q

What is the equation for the concentration of hydrogen ion?

A

[H⁺] = 10⁻ᵖᴴ

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21
Q

What is the concentration of H₂SO₄ with a pH of 1.30?

A

0.0251 mol dm⁻³

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22
Q

What is the pH of the solution formed when 250cm³ of 0.300 mol dm⁻³ H₂SO₄ is made up to 2000cm³ with water?

A

1.12

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23
Q

What is the concentration of water?

A

55.6 mol dm⁻³

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24
Q

What is the ionic product of water, Kw?

A

The product of the ions formed in the partial dissociation of water, given by Kw = [H⁺(aq)] [OH⁻(aq)]

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25
What is the ionic product of water at 298K?
Kw = 10⁻¹⁴ mol² dm⁻⁶ | Look at the units!
26
What is the Kc equation for the partial dissociation of water?
Kc = [H⁺][OH⁻] / [H₂O][H₂O]
26
What is the equation for the partial dissociation of water?
H₂O + H₂O ⇌ H₃O⁺ + OH⁻
27
What is the equation for Kw?
* Kw = [H⁺][OH⁻] * Kw = Kc [H₂O]²
28
When a solution is neutral what can be said about [H⁺] and [OH⁻]?
When neutral: [H⁺] = [OH⁻]
29
Work out the pH of water at 298K
30
In the equation "H₂O ⇌ H⁺ + OH⁻", what happens to Kw, pH and neutrality as temperature increases?
As temperature increases: * Equilibrium moves in the endothermic direction (forward direction) oppose the increase in temperature * Therefore Kw increases * [H⁺] increases so pH decreases * However it is still neutral as [OH⁻] also increases and [H⁺] = [OH⁻]
31
Calculate the pH of pure water at 40 degrees celcius when Kw = 2.09 x 10⁻¹⁴ mol² dm⁻⁶
6.84
32
What is the equation for [H⁺] in terms of Kw?
[H⁺] = √Kw
33
Calculate the pH of 0.200 mol dm⁻³ NaOH(aq) at 298K
13.30
34
Calculate the pH of 0.0500 mol dm⁻³ Ba(OH)₂(aq) at 298K
13.00
35
Calculate the pH of the solution formed when 50cm³ of 0.250 mol dm⁻³ KOH is made up to 250cm³ of solution with water at 298K
12.70
36
What is an example of a weak base?
Ammonia solution
37
What is Ka?
Acid dissociation constant, it is simply Kc applied to the dissociation of an acid (multiplied by the concentration of water)
38
What is the formula for Ka?
* Ka = [H⁺][A⁻]/[HA] * Ka = Kc x [H₂O] * Ka = [H⁺]²/[HA] (in aqueous solutions ONLY)
39
What are pKa values?
Values used to compare acid strength
40
What is the equation for pKa?
pKa = - log₁₀(Ka)
41
What is the equation for Ka in terms of pKa?
Ka = 10⁻ᵖᴷᵃ
42
What is the Ka value of a stronger acid?
higher
43
What is the pKa value of a stronger acid?
lower
44
What is the Ka value of a weaker acid?
Lower
45
What is the pKa value of a weaker acid?
Higher
46
What can be said in an aqueous solution of a weak acid?
[H⁺]eqm = [A⁻]eqm and therefore, Ka = [H⁺]²/[HA]
47
What are the assumptions in the formula "Ka = [H⁺]²/[HA]"
1. The [H⁺] from dissociation of water is insignificant 2. The amount of dissociation is so small that we can ssume that the initial concentration of the undissociated acid has remained constant
48
When can "Kw = [H⁺][OH⁻]" be used?
In all aqueous solutions
49
When can "Kw = [H⁺][H⁺]" be used?
For Pure water ONLY
50
When can "Ka = [H⁺][A⁻]/[HA]" be used?
All solutions containing a weak acid
51
When can "Ka = [H⁺]²/[HA]" be used?
For weak acids in water ONLY
52
What is the only factor which can affect Kw and Ka?
Temperature
53
Calculate the pH of 0.1 mol dm⁻³ propanoic acid (pKa = 4.87)
2.94
54
Calculate the concentration of a solution of methanoic acid with pH of 4.02 (Ka = 1.35 x 10⁻⁵ mol dm⁻³)
6.76x10⁻⁴ mol dm⁻³
55
What is an alkali?
A base that dissolves in water, forming OH⁻(aq)
56
if "HA + (aq) -> H₃O⁺(aq) + A⁻(aq)", why is the hydronium ion treated as H⁺(aq)?
A free hydrogen ion does not exist in solution, it forms a hydronium ion with water. In an aqueous solution (such as an acid) we can use hydronium ion and hydrogen ion interchangeably
57
What is H₃O⁺?
The hydronium ion
58
What is the dot and cross diagram for the hydronium ion?
59
What are 2 examples of weak acids?
* Carboxylic acids * Citric acid
60
How does an acid form its conjugate base?
By releasing a proton
61
How does a base form its conjugate acid?
By gaining a proton
62
What does H⁺(aq) actually represent?
H₃O⁺(aq)
63
Whats the equation for [H⁺(aq)] of a weak acid?
[H⁺(aq)] = √Ka[HA(aq)]
64
When does the assumption that the dissociation of water is negligible in the equation for Ka break down?
If the pH > 6, then the [H⁺(aq)] from the dissociation of water will be significant compared to the dissociation of the weak acid. **Therefore, this assumption breaks down for very weak acids or very dilute solutions**
65
When does the assumption that the concentration of an acid is much greater than the H⁺ concentration at equilibrium (and therefore [HA]start = [HA]end) break down?
This approximation only holds true for weak acids with a small Ka value, it breaks down when [H⁺(aq)] becomes significant and therefore there is a large difference between [HA]start and [HA]end. **Therefore it is not justified for stronger weak acids with Ka > 10⁻² mol dm⁻³ and for very dilute solutions**
66
When is a solution acidic?
When [H⁺] > [OH⁻]
67
When is a solution neutral?
When [H⁺] = [OH⁻]
68
When is a soluton alkaline?
When [H⁺] < [OH⁻]
69
What is pOH?
A similar scale to pH, but rather than considering the concentrations of hydrogen, it uses the concentrations of hydroxide
70
What is the relationship between pH and pOH?
pH + pOH = 14 **at 298K**
71

A Level Chemistry (31 decks)

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