Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistry HL > Acids and Bases > Flashcards

Acids and Bases Flashcards

1
Q

Bronstead Lowry Acid Def.

A

acids are proton donors

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

Bronstead Lowry Base Def.

A

bases are proton acceptors

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

Amphoteric Def.

A

act as both an acid and a base

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

Amphiprotic Def.

A

acts as both a proton donor and a proton acceptor

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

Conjugate acid and base

A

when an acid donates a proton, what remains is the conjugate base
when a base accepts a proton, what remains is the conjugate acid
(i.e. they differ by one proton - H+)

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

Condition for a species to act as a base

A

because a proton does not have any electrons of its own, it is always dependent upon some other species to provide the necessary bonding pair. For a species to be able to act as a base, it must have an unshared pair of electrons that it can supply to a proton

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

Alkalis

A

these are soluble bases, when they dissolve in water they all form hydroxide ions

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

Indicator colours

A

litmus - acid = red, alkali = blue
methyl orange - acid = red, alkali = orange
phenolphthalein - acid = colourless, alkali = pink

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

salt

A

refers to the compound formed when the hydrogen of an acid is replaced by a metal or another positive ion

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

Acid + base reaction

A

Acid + base –> salt + water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Enthalpy of neutralisation

A

the enthalpy change that occurs when an acid and base react together to form one mole of water
for reactions between strong acids and strong bases, the enthalpy is very similar = -57kJ mol
as net reaction is the same

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

Acid + metal reaction

A

acid + metal –> salt + hydrogen

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

Acid + carbonate reaction

A

acid + carbonate –> salt + water + carbon dioxide

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

pH scale

A

it is a logarithmic expression of the concentration of hydrogen ions
so pH = -log (concentration of H+)
usually positive and have no units
a change in one unit of pH represents a 10-fold change in hydrogen ion concentration

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

Kw

A

ionic product constant of water
Kw= (conc. H+) (conc. OH-)
this is because in water conc H+ = conc OH-
at 298K Kw=1X10-14

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

Dilute acids

A

show the typical properties of acids
e.g.
turn blue litmus red
react with metal to produce H2 gas
react with carbonates to release CO2 gas
they are good conductors of electricity

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

Concentrated acids

A

DO NOT show the typical properties of acids

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

Changing concentrated acids to dilute acids

A

when added to water the concentrated acid molecules donate a H+ to a water molecule. This forms hydronium ions
it is this hydronium ion that gives the acid its properties
c1V1= c2V2

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

Strong acids

A

strong acids ionize almost completely
i.e. they transfer all their protons to water
Ka is large (lies to right)
good conductors of electricity
fast rate of reaction
strong acids have low pH
e.g. HCl, HNO3, H2SO4

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

Weak acids

A

weak acids will transfer a few protons to water
i.e. they only partially dissociate in water
Ka is small (lies to left)
poor conductors of electricity
slow rate of reaction
larger pH
e.g. CH3COOH, H2CO3, H3PO4

21
Q

Strong base

A

completely dissociate in water
good conductors of electricity
very high pH
e.g. LiOH, NaOH, KOH, Ba(OH)2

22
Q

Weak base

A

only partially dissociate in water
poor conductor of electricity
lower pH
e.g. NH3, CH3CH2NH2

23
Q

Acid rain

A

refers to solutions with a pH below 5.6, which therefore contains additional acids (oxides of sulfur and nitrogen)

24
Q

Acid deposition

A

includes all processes by which acidic components as precipitates or gases leave the atmosphere
wet acid deposition: rain, snow, sleet etc.
dry acid deposition: acidifying particles, gases

25
Sulfur oxides
SO2 produced from the burning of fossil fuels S+O2 --> SO2 It dissolves in water to form sulfurous acid H2O + SO2 --> H2SO3 It can then oxidise to sulfur trioxide 2SO2 + O2 --> 2SO3 H2O + SO3 --> H2SO4
26
Nitrogen oxides
NO is mainly produced from internal combustion engines N2 + O2 --> 2NO 2NO + O2 --> 2NO2 or N2 + 2O2 --> 2NO2 it then dissolves in water to form nitrous acid and nitric acid H2O + 2NO2 --> HNO2 + HNO3 alternatively it can be oxidised to nitric acid 2H2O + 4NO2 + O2 --> 4HNO3
27
Impacts of acid deposition
1. impact on materials - both sulfur dioxide and sulfuric acid react with marble and limestone forming calcium salt, these reactions lead to the erosion of structures 2. impact on plant life - direct cause of slower growth, injury or death of plants, leaching (where important minerals in soil wash away before absorbed by plants). Dry deposition can also block plant pores needed for gas exchange 3. Impact on water - causes 'dead' lakes 4. Impact on human health - particulates in air
28
Methods to reduce SO2 emissions
hydrodesulfurization (precombustion) - catalytic process that removes sulfur from refined petroleum by reacting it with hydrogen to form hydrogen sulfide flue-gas desulfurization (postcombustion) - removes up to 90% of SO2 from flue gas in the smoke stacks of power stations before it is released
29
Methods to reduce NOx emissions
catalytic converters in cars - converts toxic emissions to relatively harmless products lower temperature combustion - NO formation is reduced at lower temperatures
30
Lews Acid Def.
is an electron pair acceptor (electrophile - electron-deficient species that accepts lone pair from another species to form a new covalent bond) *dative
31
Lewis Base def.
is an electron pair donor (nucleophile - electron rich species that donates a lone pair to form a new covalent bond) *dative
32
Lewis and Bronstead Lowry Acids
all Bronstead Lowry acids are Lewis acids, but not all Lewis acids are Bronstead Lowry acids
33
Kw and temperature
Kw is temperature dependent the dissociation of water is endothermic therefore, an increase in temperature will shift the equilibrium to the right (increase Kw) a decrease in temperature will shift the equilibrium to the left (decrease Kw)
34
Kw relationships with Ka and Kb
Kw = Ka x Kb pKw = pKa + pKb pKw = pH + pOH
35
Acidity constants
measure the extent of reactions of acids in water (therefore measure acid strength) the larger the Ka the stronger the acid the stronger the acid the smaller the pKa
36
Steps in calculating pH of weak acids
1. write hydrolysis equation 2. write the Ka expression 3. make assumptions (concentration of products are equal as 1:1 mole ratio, and concentration of reactant is the same as initial concentration as very few molecules are ionised) 4. rearrange the Ka expression and solve for concentration of H+ 5. calculate pH
37
Steps in calculating pH of weak bases
1. write hydrolysis equation 2. write the Kb expression 3. make assumptions (concentration of products are equal as 1:1 mole ratio, and concentration of reactant is the same as initial concentration as very few molecules are ionised) 4. rearrange the Kb expression and solve for concentration of OH- 5. calculate pH
38
Conjugate acid-base pairs
two species that differ by just one proton (acid is the species with the additional proton) the stronger the acid the weaker the conjugate base (and vice versa) stronger the base the weaker conjugate acid (and vice versa) strong acids produce neutral anions strong bases produce neutral cations
39
buffer solution
an aqueous solution consisting of a weak acid and its conjugate base (or a weak base and its conjugate acid) that resists changes to pH when small amounts of acid or base are added
40
Preparation of buffer solutions
a) mixing a weak acid and its conjugate base (or vice versa) there will be more of the weaker component (whichever has a larger volume, the pH of buffer will favour) b) partially neutralising a weak acid with a strong base so that some weak acid remains and the rest has been converted into its conjugate base
41
Equivalence point
is where the acid and base have neutralised each other (n(acid)=n(base))
42
Indicators
are very weak acids and have a different colour to their conjugate base
43
Buffering
is the flattish part of the titration curve where the pH hardly changes due to the presence of a weak acid and its conjugate base (can be estimated as pH = pKa +/- 1) where pKa=pH at half equivalence point
44
Strong acid - strong base pH curve
start at low pH end at high pH equivalence point at 7
45
strong acid - weak base pH curve
equivalence point < 7 has buffer region
46
weak acid - strong base pH curve
equivalence point > 7 has buffer region
47
weak acid - weak base pH curve
equivalence point = 7 no buffer region curve is squished line indicator does not work for this reaction and equivalence point must be determined with a conductivity test
48
Choosing an indicator
must: - change colour at pH value close to equivalence point (+/- pKa at equivalence) - not itself interfere with the acid - base reaction being studied

Chemistry HL (18 decks)

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