Chapter 8: Acids and Bases Flashcards
1
Q
What are hydrochloric acid HCl and sulfuric acid H2SO4 an example of?
A
Acids
2
Q
What are sodium hydroxide NaOH and ammonia NH3 an example of?
A
Bases
3
Q
What atom leads to the characteristic properties of an acid?
A
At least one hydrogen atom
* All acids contain at least one
3
Q
What atom leads to the characteristic properties of an acid?
A
At least one hydrogen atom
* All acids contain at least one
4
Q
What is the simplest definition of acids and bases?
A
Acid: a substance that produces hydrogen ions in solution
Base: a substance that produces hydroxide ions in solution
5
Q
What is the Bronsted-Lowry definition of acids and bases?
A
- An acid is a proton (H+) donor
- A base/alkali is a proton (H+) acceptor
5
Q
What is the Bronsted-Lowry definition of acids and bases?
A
- An acid is a proton (H+) donor
- A base/alkali is a proton (H+) acceptor
6
Q
What is the formula of hydrochloric acid?
A
HCl
7
Q
What is the formula of sulfuric acid?
A
H2SO4
8
Q
What is the formula of nitric acid?
A
HNO3
8
Q
What is the formula of carbonic acid?
A
H2CO3
9
Q
What is the formula of ethanoic acid?
A
CH3COOH
10
Q
What is the formula of benzoic acid?
A
C6H5COOH
11
Q
If H2O accepts a proton when CH3COOH donates a proton, which one acts as a base and which for acid?
A
H2O for acid
CH3COOH for base
12
Q
What do conjugate acid-base pairs always differ by?
A
One proton H+
13
Q
What is a conjugate acid-base pair?
A
When the acid of a compound donates a proton and it forms a base
The original acid and the base it is now are conjugate acid-base pairs
14
Q
What is the term amphiprotic and amphoteric used to describe?
A
A substance that can act as both an acid and a base
15
Q
What does amphiprotic refer to?
A
The Bronsted-Lowry definition of acids and bases and indicates a species that can donate (acting as an acid) or accept (acting as a base) a proton.
16
Q
What does amphiprotic refer to?
A
The Bronsted-Lowry definition of acids and bases and indicates a species that can donate (acting as an acid) or accept (acting as a base) a proton.
17
Q
What is a amphiprotic substance?
A
Water
because it can act as a proton donor (to form OH-) with NH3 but as a proton acceptor (to form H3O+) in its reaction with CH3COOH
18
Q
What does amphoteric refer to?
A
It is a more general term and refers to a substance that can act as an acid and a base
19
Q
What does amphoteric refer to?
A
It is a more general term and refers to a substance that can act as an acid and a base
20
Q
What is the relationship between amphoteric and amphiteric
A
All amphiprotic substances are also amphoteric but not all amphoteric substances are amphiteric
20
Q
What is the relationship between amphoteric and amphiteric
A
All amphiprotic substances are also amphoteric but not all amphoteric substances are amphiteric
21
Where does the difference arise between the term amphiteric and amphoteric?
Because there is another, more general, definition of acids and bases (the Lewis definition), which does not require the transfer of a proton
21
Where does the difference arise between the term amphiteric and amphoteric?
Because there is another, more general, definition of acids and bases (the Lewis definition), which does not require the transfer of a proton
22
What is replaced in an acid to form salt?
The hydrogen ion (H+) in an acid can be replaced by a metal ion (or ammonium ion) to for salt
22
What is replaced in an acid to form salt?
The hydrogen ion (H+) in an acid can be replaced by a metal ion (or ammonium ion) to for salt
23
What is the name of salt when hydrochloric acid loses a hydrogen ion?
Chloride
**H**Cl -> NaCl (sodium chloride)
24
What is the name of salt when sulfuric acid loses a hydrogen ion?
Sulfate
**H**2SO4 -> Na2SO4 (sodium sulfate)
25
What is the name of salt when nitric acid loses a hydrogen ion?
nitrate
**H**NO3 -> NH4NO3 (ammonium nitrate)
26
What is the name of salt when carbonic acid loses a hydrogen ion?
carbonate
**H**2CO3 -> K2CO3 (potassium carbonate)
27
What is the name of salt when ethanoic acid loses a hydrogen ion?
Ethanoate
CH3COO**H** -> Ca(CH3COO)2 (calcium ethanoate)
27
What is the name of salt when ethanoic acid loses a hydrogen ion?
Ethanoate
CH3COO**H** -> Ca(CH3COO)2 (calcium ethanoate)
28
What does a metal + acid reaction produce?
metal + acid -> salt + hydrogen
29
What does acid + carbonate/hydrogencarbonate reaction produce?
acid + carbonate/hydrogencarbonate -> salt + carbon dioxide + water
30
What does a base + water reaction form?
Base + acid -> Salt + water
31
What are metal oxides or metal hydroxides?
Bases
32
What are alkalis?
Solutions obtained when a metal hydroxide (such as sodium hydroxide) dissolves in water or when certain bases react with water
33
What are alkalis?
Solutions obtained when a metal hydroxide (such as sodium hydroxide) dissolves in water or when certain bases react with water
34
What does the fact that there are very few soluble metal hydroxides mean for alkalis?
There are very few alkalis
35
What does the fact that there are very few soluble metal hydroxides mean for alkalis?
There are very few alkalis
36
Base vs alkali which is the most general term?
Base
37
What is the reaction between an acid and an alkali?
It is similar to that between an acid and a base
Alkali + acid -> salt + water
37
What is the reaction between an acid and an alkali?
It is similar to that between an acid and a base
Alkali + acid -> salt + water
38
What are the reactions between acids and bases or acids and alkalis called?
Neutralisation reactions
38
What are the reactions between acids and bases or acids and alkalis called?
Neutralisation reactions
39
What are neutralisation reactions?
When the H+ ions from the acid reacts with the OH- ions from the alkali to form a neutral substance water
40
What are neutralisation reactions?
When the H+ ions from the acid reacts with the OH- ions from the alkali to form a neutral substance water
41
Is neutralisation reactions exo or endo?
Exothermic and typically give out about 57kJ per mole of water formed
41
Is neutralisation reactions exo or endo?
Exothermic and typically give out about 57kJ per mole of water formed
42
What do neutralisation reactions produce?
a salt and water only
43
What do neutralisation reactions produce?
a salt and water only
44
What is ammonia solution equivalent to? (NH3 aq)
to ammonium hydroxide (NH4OH)
in some labs it is labelled as ammonia solution and ammonium hydroxide in others
44
What is ammonia solution equivalent to? (NH3 aq)
to ammonium hydroxide (NH4OH)
in some labs it is labelled as ammonia solution and ammonium hydroxide in others
45
What is ammonia in equilibrium with?
the ammonium ion and the hydroxide ion
45
What is ammonia in equilibrium with?
the ammonium ion and the hydroxide ion
46
Generally where does the metal part of the salt come from and the non-metal part?
Metal part comes from a metal oxide or hydroxide and th enon-metal part from the acid
e.g.
cooper sulfate can be made from the reaction between the base copper oxide and the sulfuric acid
47
WHat is one common way of making a soluble salt?
By tritrating an acid against an alkali
* a known amount of acid is measured out using a pipette and then an indicator is added
* the alkali is then added from a burette until the indicator just changes colour
48
What are indicators?
essentially substances that have different colours in acidic and alkaline solutions
* used commonly in titrations
48
What are indicators?
essentially substances that have different colours in acidic and alkaline solutions
* used commonly in titrations
49
How are different indicators chosen for a titration?
Based on whether the acid or the alkali is weak or strong
50
What does a universal indicator contain?
a mixture of indicators and cannot be used to monitor titrations because it changes gradually from one colour to the next
50
What does a universal indicator contain?
a mixture of indicators and cannot be used to monitor titrations because it changes gradually from one colour to the next
51
What can the pH scale be used for?
to indicate whether a solution is acidic, alkaline or neutral
51
What can the pH scale be used for?
to indicate whether a solution is acidic, alkaline or neutral
52
What can the pH of a solution be determined by?
A pH meter or by using universal indicator solution or paper
53
What can the pH of a solution be determined by?
A pH meter or by using universal indicator solution or paper
54
What is pH a measure of?
the concentratino of H+ ions in a solution
54
What is pH a measure of?
the concentratino of H+ ions in a solution
55
What is the unit of pH?
there is no units
56
What is the unit of pH?
there is no units
57
What does it mean when water dissociates ( or ionsises)?
58
What is the relatinship of H+ to OH- in a neutral solution?
59
What is the relatinship of H+ to OH- in a acidic solution?
60
What is the relatinship of H+ to OH- in a alkaline solution?
61
What can be assumed for strong acids to do in aqueous solutions?
Strong acids can be assiumed to dissociate fully in aqueous solution
62
What can be assumed for strong acids to do in aqueous solutions?
Strong acids can be assiumed to dissociate fully in aqueous solution
63
Because strong acids can be assumed to dissociate fully in aqueous solution, what is the concentration of H+ ions and the concentration of the acid?
the conc. of H+ ions is the same as the concentration of the acid
64
What happens when an acid reacts with water?
It dissociates, or ionises
65
Why does an acid dissociate when reacting with water?
Using the Bronsted-Lowry theory
* the acid donates a proton to water
* acid dissociates into H+ and A- ions
65
Why does an acid dissociate when reacting with water?
Using the Bronsted-Lowry theory
* the acid donates a proton to water
* acid dissociates into H+ and A- ions
* and the H+ from the acid is donates to H2O
66
How can we classify how strong or weak an acid is?
By how much they dissociate in aqueous solution
67
What are 3 strong acids that dissociate completely in aqueous solution?
* hydrochloric acid (HCl)
* sulfuric acid (H2SO4)
* nitric acid (HNO3)
68
What is a monoprotic acid and what is an example of it?
HCl is a monoprotic acid
* it dissociates to form one proton per molecule
68
What is a monoprotic acid and what is an example of it?
HCl is a monoprotic acid
* it dissociates to form one proton per molecule
69
What is a diprotic acid and what is an example of it?
H2SO4 is a diprotic acid
* it can dissociate to form two protons per molecule
70
What is the difference between a monoprotic acid and a diprotic acid?
when it dissociates to either forms one proton per molecule (monoprotic) or two proton per molecule (diprotic)
71
How do weak acids dissociate in aqueous solutions?
Only partially
72
How do weak acids dissociate in aqueous solutions?
Only partially
73
What is sulfuric acid a strong acid for?
for the first dissociation only
74
What are examples of weak acids?
* carbonic acid (H2CO3)
* carboxylic acids such as ethanoic acid (CH3COOH)
75
How can we spot a weak or strong acid dissociating from an equation?
by the arrow
* the non-reversible arrow (->) is used to indicate that the dissociation is essentially complete
* the equilibrium arrow indicates that the reaction is reversible and does not go to completion
76
Is HCO3- amphiprotic?
the hyrogen carbonate ion is amphiprotic. it accepts a proton in the reverse reaction in the first equation (acts as a base) and donates a proton (acts as an acid) in the second
76
Is HCO3- amphiprotic?
the hyrogen carbonate ion is amphiprotic. it accepts a proton in the reverse reaction in the first equation (acts as a base) and donates a proton (acts as an acid) in the second
76
Is HCO3- amphiprotic?
the hyrogen carbonate ion is amphiprotic. it accepts a proton in the reverse reaction in the first equation (acts as a base) and donates a proton (acts as an acid) in the second
76
Is HCO3- amphiprotic?
the hyrogen carbonate ion is amphiprotic. it accepts a proton in the reverse reaction in the first equation (acts as a base) and donates a proton (acts as an acid) in the second
77
What happens when a base reacts with water?
It accepts a proton from the water and ionises
78
How are bases defined as strong or weak?
depending on how much they ionic in aqueous solution
79
What do strong bases do in aqueous solution?
They ionise completely
80
What do strong bases do in aqueous solution?
They ionise completely
81
What do weak bases do in aqueous solution?
Ionise only partially
82
Is ammonia a base or acid?
It is a typical weak base
83
Is ammonia a base or acid?
It is a typical weak base
84
What are examples of weak bases?
* ammonia
* amines such as ehylamine (ethanamine) CH3CH2NH2
85
WHat is the relationship between the strength of an acid and the strength of its conjugate base?
The stronger an acid, the weaker its conjugate base
86
What is the relationship between the strength of an acid and the strength of its conjugate base?
The stronger an acid, the weaker its conjugate base
87
What is the relationship between the strength of a base and the strength of its conjugate acid?
The stronger a base, the weaker its conjugate acid
88
What does the methods for distinguishing between acids rely on?
on the fact that strong acids dissociate more than weak acids
89
How is a strong acid a better conductgor of electricity than a weak acid?
* strong acids dissociates fully
* so the concentration of ions is high
* making it a good conductor of electricity
* A weak acid only dissociates partially and so the conc. of ions is lower and does not conduct electricity as ell
90
Because strong acids are good conductors of electricity, what may they be described as?
strong electrolytes
weak electrolytes for weak acids
91
If the pH is lower, what does it mean for the concentration of H+?
the lower the pH, the higher the concentration of H+ ions
91
If the pH is lower, what does it mean for the concentration of H+?
the lower the pH, the higher the concentration of H+ ions
92
Why do strong acids react more rapidly with metals such as magnesium to form hydrogen?
Because strong acids have a higher concentration of free H+ ions and therefore react more rapidly
93
What is effervescence?
rapid bubbling
93
What is effervescence?
rapid bubbling
94
What are rapid reactions shown by?
effervescence
95
What does the concentration of an acid refer to?
the number of moles of acid in a certain volumr
96
What does the strength of an acid refer to?
How much it dissociayes in squeous solution
97
Can a more concentrated solution become a stronger acid?
No matter how concentrated the solution of ethanoic acid is, it will never become a storng acid because it always dissociayes partially
simlarily, diluting a strong acid does not make it anything other than a strong acid because it always dissociates fully
97
Can a more concentrated solution become a stronger acid?
No matter how concentrated the solution of ethanoic acid is, it will never become a storng acid because it always dissociayes partially
simlarily, diluting a strong acid does not make it anything other than a strong acid because it always dissociates fully
98
Does a lower pH mean a stronger acid?
No pH is simple a measure of the concentration of H+ ions. It is possible for a dilute solution of a strong acid to have a higher pH than a concentration nsolution of a weak acid.
98
Does a lower pH mean a stronger acid?
No pH is simple a measure of the concentration of H+ ions. It is possible for a dilute solution of a strong acid to have a higher pH than a concentration nsolution of a weak acid.
99
How is a more concentrated soltuion of a weak acid able to have a lower pH?
Because the partial dissociation of the weak acid produces a high concentration of H+ than the complete dissociation of the strong acid HCl
100
How can pH be used to compare acid strength?
Only if equal concentrations of acids are being compared
101
How can pH be used to compare acid strength?
Only if equal concentrations of acids are being compared
102
What do oxides of non-metals, if soluble in water produce?
Acidic solutions
* oxides of non-metals are acidic
103
How is rain naturally acidic?
Because of dissolved carbon dioxide
104
How is rain naturally acidic?
Because of dissolved carbon dioxide
105
What is acidic deposition?
* any process in which acidic substances (particles, gases and preipitation) leave the atmosphere to be deposited on the surface of the earth
* divided into wet depoition (acid rain, fog and snow) and dry deposition (acidic gases and particles)
106
What do acidic pollutants include?
Oxides of sulfur and nitrogen
107
What can sulfur dioxide be formed by?
various natrual and anthropogenic processes - such as burning of sulfuer-containing fuels
108
What are the main anthropogenic sources of nitrogen oxides?
internal combustion engine, coal, gas, oil-fuelled power stations and heavy industry power generation
109
How can sulfuric acid be formed?
110
How is nitric acid formed?
When NO2 react with a hydroxyl free radical
111
What are the problems associated with acid deposition?
Effect on vegetation
* the acid can displace metal ions from the soil that are consequently washed away
* Mg2+ is need to produce chlorophyll but its washed away by acid displacing it and so plants could be prevented from phootsynthesising properly
* Aluminium ions are dissolved from rocks which damages plant roots and limits water uptake. Cause stunted growth and thinning or yellowing of leaves on trees
Lakes and rivers
* aquatic life is sensitive to the pH falling below 6
* insect larvae, fish and invertebrates and others cannot survive below pH 5.2
* below pH 4, virtually no life will survive
* dissolve haardous minerals from rocks and acculate in lakes and damage aqautic life (Al3+ ions damage fish gills)
buildings
* Limestone and marble are eroded and sisolve away expsoing a fresh surface to react with more acid
human health
* irritates mucous membranes
* cause respiratory illnesses such as asthma and bronchitis
* can dissolve heavy metal compounds releasing poisonous ions which ay be linked to Alzheimer's disease
111
What are the problems associated with acid deposition?
Effect on vegetation
* the acid can displace metal ions from the soil that are consequently washed away
* Mg2+ is need to produce chlorophyll but its washed away by acid displacing it and so plants could be prevented from phootsynthesising properly
* Aluminium ions are dissolved from rocks which damages plant roots and limits water uptake. Cause stunted growth and thinning or yellowing of leaves on trees
Lakes and rivers
* aquatic life is sensitive to the pH falling below 6
* insect larvae, fish and invertebrates and others cannot survive below pH 5.2
* below pH 4, virtually no life will survive
* dissolve haardous minerals from rocks and acculate in lakes and damage aqautic life (Al3+ ions damage fish gills)
buildings
* Limestone and marble are eroded and sisolve away expsoing a fresh surface to react with more acid
human health
* irritates mucous membranes
* cause respiratory illnesses such as asthma and bronchitis
* can dissolve heavy metal compounds releasing poisonous ions which ay be linked to Alzheimer's disease
112
What are the methods of dealing with acid deposition?
* improving the design. ofbehicle engines
* using catalytic converters
* removing sulfur before burning fuels
* using renewable power supplies
* making greater use of public transport
* designing more efficient power stations
* 'liming' of lakes - calcium oxide or hydroxide neutralises acidity
113
What is pre-combustion desulfurisation?
removing sulfur before the fuel is burnt to produce a more environmentally-friendly fuel
113
What is pre-combustion desulfurisation?
removing sulfur before the fuel is burnt to produce a more environmentally-friendly fuel
114
What is post-combustion desulfurisation?
removing SO2 after the fuel is burnt
