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Chemistry (Physical) > Acids and Bases > Flashcards

Acids and Bases Flashcards

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1
Q

What is a Bronsted lowry acid

A

Proton donor

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2
Q

What is a Bronsted lowry base

A

Proton acceptor

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3
Q

How do H+ ions exist in water

A

As H3O+ ions

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4
Q

What is the general equation for the reaction of an acid with water

A

HA(aq) + H2O(l) —> H3O+(aq) + A-(aq)

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5
Q

What is the general equation for the reaction of a base with water

A

B(aq) + H2O(l) —-> BH+(aq) + OH-(aq)

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6
Q

What is a strong base

A

A base which fully dissociates into its ions in solution

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7
Q

What is a weak base

A

A base which partially dissociates into its ions in solution

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8
Q

What is a strong acid

A

An acid which fully dissociates into its ions in solution

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9
Q

What is a weak acid

A

An acid which partially dissociates into its ions in solution

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10
Q

Is CH3COOH a strong or weak acid

A

Weak acid

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11
Q

What is the equation for the dissociation of ethanoic acid

A

CH3COOH ⇌ CH3COO- + H+

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12
Q

In general, are carboxylic acids weak or strong

A

Weak acids

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13
Q

Give 3 examples of strong acids

A

HCl
H2SO4
HNO3

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14
Q

Why are carboxylic acids weak

A

Backwards reaction favoured and so only partial dissociation occurs, meaning not many H+ produced (equilibrium lies to the left)

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15
Q

What is the equation for the dissociation of HCl

A

HCl ⇌ H+ + Cl-

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16
Q

Why are HCl, H2SO4, HNO3 strong acids

A

Forwards reaction strongly favoured and full dissociation occurs, meaning many H+ produced
(equilibrium lies to the right)

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17
Q

Give 2 examples of strong bases

A

NaOH
KOH

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18
Q

What is the equation for the dissociation of NaOH

A

NaOH ⇌ Na+ + OH-

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19
Q

Why are NaOH and KOH strong bases

A

Forwards reaction strongly favoured and full dissociation occurs, meaning many OH- produced
(equilibrium lies to the right)

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20
Q

Give an example of a weak base

A

NH3

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21
Q

What is the equation for the dissociation of ammonia

A

NH3 + H2O ⇌ NH4+ OH-

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22
Q

Why is NH3 a weak base

A

Backwards reaction favoured and so only partial dissociation occurs, meaning not many OH- produced
(equilibrium lies to the left)

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23
Q

What does ammonia require to produce OH-

A

The presence of water

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24
Q

What ion does NH3 form

A

NH4+

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25
What is the general equation for when acids and bases react
HA(aq) + B(aq) ⇌ BH+(aq) + A-(aq)
26
What is the role of water when it reacts with an acid
Water acts as a base
27
What is the equation for pH
pH = -log[H+]
28
What is the equation for [H+]
[H+] = 10⁻ᵖᴴ
29
What is the equation for the dissociation of H2O
H2O ⇌ H+ + OH-
30
What is the equation for Kᵥᵥ
Kᵥᵥ = [H⁺]² This is due to Kᵥᵥ = [H⁺][OH⁻] and [H⁺] = [OH⁻] in the equation: H2O ⇌ H+ + OH- So we can write Kᵥᵥ = [H⁺]²
31
What is the value of Kᵥᵥ at 25 degrees celcius
1x10⁻¹⁴
32
What is a monoprotic acid
Monoprotic acids dissociate to produce one H+ ion for every acid molecule
33
Give 2 examples of monoprotic acids
HCl HNO3
34
What is a diprotic acid
Diprotic acids dissociate to produce two H+ ion for every acid molecule
35
When we have the concentration of a diprotic acid, how do we get pH
Multiply concentration of acid by 2, then put into log equation
36
Give an example of a diprotic acid
H2SO4
37
Which equations do we use to calculate the pH of strong bases
Kw equation to get H+ conc pH equation to get pH
38
What equation do we use to calculate the pH of strong acids
Kw equation to get H+ conc pH equation to get pH
39
What do we use Kₐ for
Calculating H+ conc for weak acids
40
Why do we use Kₐ and now Kw for weak acids
Weak acids only partially dissociate and so the [H+] we would get from the Kw equation is not equal to the concentration of the acid
41
What is the equation for Kₐ
42
What is the units for Kₐ
moldm-3
43
What is the dissociation equation for weak acids
HA ⇌ H⁺ + A⁻
44
What is the weak acid approximation equation for Kₐ
45
What is the equation for pKₐ
-logKₐ
46
What is the equation for Ka if we know pKa
10⁻ᵖᴷᵃ
47
If the value of Ka is smaller, what does this mean about the strength of a weak acid
It is a weaker, weak acid
48
If the value of pKa is smaller, what does this mean about the strength of a weak acid
It is a stronger, weak acid
49
If the value of Ka is larger, what does this mean about the strength of a weak acid
It is a stronger, weak acid
50
If the value of pKa is larger, what does this mean about the strength of a weak acid
It is a weaker, weak acid
51
Draw the pH curve for a strong base being added to a strong acid
52
Draw the pH curve for a weak base being added to a strong acid
53
Draw the pH curve for a strong base being added to a weak acid
54
Draw the pH curve for a weak base being added to a weak acid
55
What is the equivalence point on a pH curve
The point at which an acid/base has been neutralised by a base/acid respectively
56
Where is the equivalence point on a pH curve
At the start of when the curve becomes completely vertical
57
What is the half neutralisation point on a pH curve and what do we use it for
It is the half way point between the equivalence point and 0 We can find the pH at this point to calculate pKa of a WEAK ACID
58
Explain the relationship between pKa and pH for weak acids at the half neutralisation point on a pH curve
59
How do we correctly determine which indicator to use from a pH curve
The indicator must change colour entirely within the vertical part of a pH curve
60
What are the colour changes of methyl orange and what reactions would this indicator be suitable for
Red at low pH Yellow at high pH Suitable for: Strong acid/strong base Strong acid/weak base
61
What are the colour changes of phenolphthalein and what reactions would this indicator be suitable for
Colourless at low pH Pink at high pH Suitable for: Weak acid/strong base
62
What is Methyl orange's colour change range
Methyl orange's colour change range is from red to yellow over a pH range of 3 to 4.4
63
What is phenolphthalein's colour change range
Phenolphthalein's colour change range is from red to yellow over a pH range of 8.3 to 10
64
Why is there no indicator suitable for a weak acid - weak base titration
Weak acid - weak base titrations have no sharp pH change, therefore we have to use a pH meter
65
Why do diprotic acids have two equivalence points in their pH curves
The 2 protons are released from the molecule separately (they don't leave at the same time) All the molecules release the same proton on the same part of the molecule first, once all are done, then second proton comes off
66
What is a buffer solution
A solution that resists changes in pH on addition of small amount of acid, base or on dilution with water
67
What is the dissociation equation for method 1 (acidic buffer) of making a buffer
68
What is the equation for calculating the H+ concentration of a buffer
Then -log(H+)
69
What is the dissociation equation for a buffer made by method 2 (basic buffer)
70
What are the 5 steps in calculating the pH of a buffer made from method 2 (basic buffer) (assuming we know the concentration and moles of HA & A-)
1 - Calculate the moles of HA(start) (C =n/V) 2 - Calculate the moles of OH- (C=n/V of base, but check ratio of base to OH) 3 - Calculate moles of HA(end) (nHA(start) - nOH-) 4 - Write down nA- (nA- = nOH-) 5- Use buffer equation to find concentration of H+, then put into log equation
71
What are the steps in calculating the pH of a buffer made by method 1 (acidic buffer)
Then -log(H+)
72
What is the equation to calculate H+ concentration of a buffer solution after adding an acid
73
What is the equation to calculate H+ concentration of a buffer solution after adding a base
74
Which way does equilibrium shift when we add an acid to a buffer solution, what effect does this have on the concentration of HA
Upon addition of an acid, equilibrium shifts left, and HA concentration increases
75
Which way does equilibrium shift when we add a base to a buffer solution, what effect does this have on the concentration of HA
Upon addition of a base, equilibrium shifts to the right and HA concentration decreases
76
Give 2 uses for buffers
Shampoo Washing powder
77

Chemistry (Physical) (13 decks)

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