Acids and Bases Flashcards
1
Q
Properties of acids (acidic solutions)?
A
- sour/bitter
- corrosive
- neutralise bases
- pH < 7
2
Q
Properties of bases (alkaline solutions)?
A
- slippery
- corrosive
- neutralise acids
- pH > 7
3
Q
properties of Neutral solutions?
A
- pH = 7
- Indicators can be used to determine if a solution is acid, basic or neutral.
4
Q
what are Lab acids?
A
HCl, HNO3, H2SO4
5
Q
Bronsted-Lowry theory of acids?
A
“An acid is a substance that is able to donate a proton/hydrogen ion (H+) to another substance.”
6
Q
conjugate base of HCl ?
A
Cl-
7
Q
conjugate base of HNO3 ?
A
NO3-
8
Q
conjugate base of H2SO4?
A
HSO4-
9
Q
Lab bases?
A
NaOH, KOH, NH3
10
Q
Bronsted-Lowry theory of base?
A
“A base is a substance that is able to accept a proton/hydrogen ion (H+) from another substance.”
11
Q
conjugate acid of NH3?
A
NH4+
12
Q
conjugate acid of HCO3- ?
A
H2CO3
13
Q
conjugate acid of OH-?
A
H2O
14
Q
what are Acid-base reactions often called?
A
Often called “neutralisation” reactions
15
Q
what pattern do Acid-base reactions follow?
A
Follow the pattern: acid + base → salt + water
eg. HCl + NaOH → NaCl + H2O
16
Q
what is another version of the acid-base reactions?
A
Bronsted-Lowry acids and bases
17
Q
is water an acid or a base?
A
Water is amphiprotic. How it behaves will depend on what its mixed with.
18
Q
define Amphiprotic
A
species that can act as both an acid and a base
19
Q
what is H3O+?
A
hydronium ion
20
Q
what is OH- ?
A
hydroxide ion
21
Q
what do Strong acids do?
A
donate all available protons
22
Q
Strong Lab acids?
A
HCl, HNO3, H2SO4
23
Q
what are the two types of strong lab acids?
A
- Monoprotic
- diprotic
24
Q
what is Monoprotic?
A
1 x H+ to donate
25
what is diprotic?
2 x H+ to donate
26
strong acids features?
- Reactions go to completion
- There is no acid (eg HCl) in hydrochloric acid solution
- H3O+ (hydronium ion) is what identifies an acidic solution
27
what are Weak acids?
donate only a few of the available protons
28
what are some weak acids?
Most other acids that are not strong acids, carboxylic acids, CH3COOH
29
weak acids features?
- Reactions are not complete
- All species present
- H3O+ still identifies acidic solution
30
what are Strong bases?
accept all available protons
31
strong lab bases?
NaOH, KOH, Cu(OH)2
32
strong bases features?
- Reactions go to completion
- Water over the arrow
- OH- (hydroxide ion) is what identifies an basic solution
33
what are Weak bases?
accept only a few of the available protons
34
lab weak bases?
Most other bases are weak eg. NH3, carbonates
35
weak bases features?
- Reactions are not complete
- All species present
- OH- still identifies basic solution
36
how does water react with itself?
- Water is amphiprotic (can act as an acid or a base).
H2O + H2O ⇄ OH- + H3O+
- Water reacts with itself, you will find H2O, OH- and H3O+ species in pure water.
37
what is water reacting with itself called?
This is called the self ionisation (or autodissociation) of water.
38
what type of acid/base is water and what does this mean?
Water is a weak acid and a weak base.
- Water donates only a few available protons/H+ ions
- Water accepts only a few available protons/H+ ions
This actually only occurs very very rarely!
39
what makes water neutral in water reaction?
[H3O+] = [OH-] This makes water neutral.
40
what is the concentration of H3O+ and OH- of water at 25 degrees?
[H3O+] = 1 x 10-7 molL-1
[OH-] = 1 x 10-7 molL-1
Kw = [H3O+] x [OH-] = 1 x 10-14 molL-1
41
what makes a solution acidic?
Since [H3O+] > [OH-] solution is acidic.
42
when does water react with itself in equations?
almost always as a second step when no more acid/base can be reacted with (in solutions)
43
strong vs weak acids Electrical conductivity?
Strong acid - Higher
Weak acid - Lower
44
strong vs weak acids Rate of reaction with metals, carbonates?
Strong acid - Higher
Weak acid - Lower
45
strong vs weak acids pH?
Strong acid - Lower (0 - 3)
Weak acid - Higher (4 - 6.9)
46
relationship between acids and their conjugate bases?
a strong acid will always have a weak conjugate base and vice versa
47
Relationships in water based solutions of acids and bases?
Pure water at 250C:
[H3O+] = [OH-]
An acidic solution at 250C:
[H3O+] > [OH-]
An basic/alkaline solution at 250C:
[H3O+] < [OH-]
48
what does Kw equal?
Kw = [H3O+] x [OH-] = 1 x 10-14 molL-1
49
what is pH?
pH is actually a measure of the [H3O+] in a solution
50
relationships of pH?
↑ [H3O+] ∴ ↓ pH ↓ [H3O+] ∴ ↑ pH
51
how is pH calculated?
pH = - log[H3O+]
52
For any strong acid solution equation?
HA + H2O → A- + H3O+
53
what happens to pH in strong acid solutions?
Notice that HA : H3O+ is 1 : 1
This means that [HA] = [H3O+] given that strong acids donate their H+/proton very very effectively
NB: there is a tiny bit extra H3O+ due to self ionisation of water but we will ignore it as it is so small. There is also traces of OH-.
54
how do calculate [H3O+] from pH?
[H3O+] = 10-pH
55
pattern of Acid + Oxide/Hydroxide (base) reaction?
acid + oxide/hydroxide → salt + water
56
what are Oxides and hydroxides?
Oxides and hydroxides are bases
57
Observations of Acid + Oxide/Hydroxide (base) reaction?
Observations will vary depending on the concentration of the solutions or state of chemicals.
58
pattern of Acid + Carbonate (base) reaction?
acid + carbonate → salt + carbon dioxide + water
59
what are Carbonates and bicarbonates?
bases
60
Observations of Acid + Carbonate (base) reaction?
Bubbles (due to CO2(g))
61
what do full equations show?
Full equations show all species present in a reaction (both ionic and covalent species), irrespective of their state.
62
what do ionic equations show?
Ionic equations are simplified versions of an equation.
Ionic equations do not include spectator ions.
63
what are spectator ions?
Spectator ions are ions that stay in the same state (often (aq)) throughout the reaction, hence do not form part of a new product.
64
what are Acid + base reactions often called?
Acid + base reactions are often called neutralisation reactions.
65
Do acids and bases cancel?
Acids and bases “cancel” each other out.
So given: acid + base → salt + water
The products of an acid + base reaction must be neutral, right?
Meaning pH = 7
Well sometimes!
66
Do all acids and bases cancel?
- Acid + base reactions involving either a weak acid and/or a weak base do not result in neutral products with a pH = 7
- Even if you use the correct ratio of acid to base (eg. concentrations, volumes and moles).
67
why do weak acid/base reactions never neutralise?
This occurs because the salt product (eg. NH4Cl) has either acidic or basic characteristics itself.
