Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A-Level Chemistry > Topic 12 Acid-Base Equilibria > Flashcards

Topic 12 Acid-Base Equilibria Flashcards

(57 cards)

Start Studying
1
Q

Define an acid

A

a substance that can donate a proton i.e. a proton donor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define an alkali

A

a substance that can accept a proton i.e. a proton acceptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a requirement of an alkali/proton acceptor?

A

needs to have a lone pair of electrons to accept a proton and form a dative covalent bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a conjugate acid-base pair?

A

consists of either a base and its conjugate acid or an acid and its conjugate base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a conjugate acid?

A

when a base accepts a proton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a conjugate base?

A

when an acid donates a proton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define an amphoteric substance

A

a substance that can act as a base and an acid e.g. water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What ion causes a solution to be acidic?

A

H+ ion, hydrogen ion or H3O+ ion, oxonium ion (protons react with H2O to form it)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What ion causes a solution to be alkaline?

A

OH- ion, hydroxide ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Write an equation for the ionisation of water

A 
2 H2O(l) ---> H3O+(aq) + -OH(aq) OR
H2O(l) ---> H+ (aq)+ -OH(aq)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Define a monoprotic acid

A

an acid that releases one H+ ion per molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define a diprotic acid

A

an acid that releases two H+ ions per molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do you work out pKa?

A

pKa= -lgKa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do you work out pH using H+ ions?

A

pH= -lg[H+] or pH=lg 1/H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is Kw/ how do you work it out?

A

Kw is the ionic product of water Kw=[H+(aq)][OH-(aq)]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the equation to work out pH using acid and salt concentrations?

A

pH=pKa-lg[acid]/[salt]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a buffer solution?

A

a solution that minimises the change in pH when a small amount of either acid or base is added

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do acid-base reactions involve the transfer of?

A

protons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 2 equations for the ionisation of water?

A

1) H2O(l) –> H+(aq) + OH-(aq)

2) 2H2O(l) –> H3O-(aq) + OH-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is Kw value for water?

A

Kw= [H+][OH-]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the value of Kw at 298K?

A

1.00 x 10-14 (to the power of -14)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What physical factor effects the value of Kw and how?

A

temperature, an increased temperature moves the equilibrium to the right so Kw increases and the pH of pure water decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How do you calculate pKw?

Study These Flashcards
A 
pKw= -logKw
Kw= 10-pKw (to the power of -pKw)
24
Q

If 2 solutions have a pH difference of 1, what is the difference in [H+]?

Study These Flashcards
A

a factor of 10

25
What is different when finding [H+] from the concentration of diprotic and triprotic acids?
need to multiply the concentration of the acid by the number of protons to find [H+]
26
Define a strong acid
one which fully dissociates in water
27
Define the term strong base
one which fully dissociates in water
28
What is the difference between strong and concentrated?
concentrated means many mols per dm3. strong refers to the amount of dissociation
29
What is a weak acid and weak base?
one which partially dissociates
30
Give some examples of strong acids
- HCL - H2SO4 - H3PO4
31
Give some examples of strong bases
- NaOH - CaCO3 - NaCO3
32
Give some examples of weak acids
- CH3COOH | - any organic acids
33
Give some examples of weak bases
-NH3
34
What is Ka
acid dissociation constant: | Ka=[H+][A-]/[HA]
35
Define equivalence point
the point at which the exact volume of base is added to the acid to neutralise it, or acid added to base
36
What generally happens to the pH of the solution around the equivalence point?
there is a large and rapid change in pH, except in a weak base and weak acid titration
37
What is the end point?
the volume of acid or alkali added when the indicator just changes colour, with the right indicator equivalence point= end point
38
State the properties of a good indicator
- sharp colour change- no more than a drop of acid or alkali needed to change colour - end point must be the same as the equivalence point - distinct colour change
39
What indicator would be used for a strong-acid strong-base titration?
phenolphthalein or methyl orange- phenolphthalein is the clearest colour change
40
What indicator would be used for a strong-acid and weak-base titration?
methyl orange
41
What indicator would be used for a strong base and weak-acid titration?
phenolphthalein
42
What indicator would be used for a weak base and weak acid titration?
neither would be suitable as there is no steep change
43
What is the half-neutralisation point?
when volume= half the volume that has been added at the equivalence point
44
Define a buffer solution
a solution that resists changes to pH when small amounts of acid or alkali are added
45
What do acidic buffer solutions contain?
- weak acid | - soluble salt that an acid fully dissociates
46
Write an equation for an acidic buffer with added alkali
HA + OH- --> H2O + A-
47
What do basic (base) buffer solution contain?
- weak base | - soluble salt of that weak base
48
How can you calculate the pH of buffer solutions?
use the Ka of the weak acid, sub in [A-] and [HA], calculate [H+] --> pH
49
How can you calculate the new pH of a buffer solution when acid or base is added?
calculate the number of moles of H+ and A- and HA before acid or base is added (initial moles). use equations to work out the new moles of A- and HA, work out [H+] --> pH
50
Why is there a difference in enthalpy changes of neutralisation values for strong and weak acids?
- enthalpy changes of neutralisation are always exothermic, value is similar for weak and strong acids because same reaction is occurring: H+ + OH- --> H2O - weak acids have a less exothermic value because energy is absorbed to ionise the acid and break the bond to the hydrogen in the un-dissociated acid
51
What does a lower pKa value tell you?
that the acid is strong
52
Give the equation for the ionisation of HCl
HCl(aq) --> H+(aq) + Cl- (aq)
53
What does a large Ka value tell you?
that the acid is strong (small pKa value also tells you the acid is strong)
54
What is a neutral solution?
where the concentration of hydrogen ions and hydroxide ions are equal
55
How do you determine pKw?
pKw= -lgKw
56
What does diluting a strong acid by a factor of 10 do?
increase the pH by 1
57
What does diluting a weak acid by a factor of 10 do?
increase the pH by 0.5

A-Level Chemistry (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions