hl chemistry > unit 8 > Flashcards

unit 8 Flashcards

(55 cards)

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1
Q

arrhenius definition of acids and bases

A
  • acids produce H+ and bases produce OH-
  • only focused on aqueous solutions
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2
Q

bronsted-lowry theory of acids and bases

A
  • acids are proton donors and bases are proton acceptors
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3
Q

conjugate acid-base pair

A

two chemical species that differ by a single proton

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4
Q

amphiprotic vs amphoteric

A

species that can accept and donate a proton (acting as acid and base) vs. species that can act as both acids and bases in general

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5
Q

features that make a species amphiprotic

A
  • must have lone pair of electrons to accept H+ and be able to release a H+ (must be able to dissociate)
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6
Q

examples of bases

A
  • metal oxides, hydroxides
  • ammonia
  • g1 carbonates, g1 hydrogen carbonates
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7
Q

what is a salt

A

ionic compound formed when hydrogen of an acid is replaced by metal or another positive ion

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8
Q

what is Kw

A

the ion product constant for water –> represents equilibrium constant for self-ionization of water

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9
Q

what does self-ionization of water mean for the presence of hydronium and hydroxide ions

A

they are both always present in all aqueous systems, however concentrations depend on acidic/basic nature of solution

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10
Q

ionization of strong vs weak acids+bases

A

strong: completely ionize/dissociate to form ions
weak: hold onto proton strongly, weak proton transfer

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11
Q

what are the 7 strong acids

A

HCl, HI, HBr, H2SO4, HClO4, HClO3, HNO3

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12
Q

what are the strong bases

A

all group 1 + last 4 of group 2 metal hydroxides

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13
Q

electrical conductivity of strong/weak acids+bases

A

strong: produces more ions, bright light
weak< produces less ions, dim light

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14
Q

what do Ka and Kb represent

A

the acid/base dissociation constant –> the extent to which an acid/base fully ionizes

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15
Q

how does Kw change as temp changes

A
  • dissociation of water is endothermic
  • as temp increases, position of eq’m shifts towards product –> larger Kw
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16
Q

how does pH of water change with temperature

A

as temperature increases, pH decreases (more acidic)
- produced more H+

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17
Q

what doe pKa and pKa represent

A
  • the negative logarithms of Ka and Kb as those values are often small
  • a measure of acid/base strength <– inverse to Ka/Kb
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18
Q

a strong acid has a ____ Ka value and a ____pKa value

A

high, low

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19
Q

the _____ an acid, the ____ the conjugate base

A

weaker, stronger

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20
Q

where do the cation and anion from a salt come from

A

cation: from the base
anion: from the acid

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21
Q

what is needed to create neutral/acidic/basic salts

A

neutral: strong acid + strong base
acidic: strong acid + weak base
basic: weak acid + strong base

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22
Q

what do buffer solutions do

A
  • resist changes to pH when small amounts of acid or base are added
  • needed in many biological systems
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23
Q

how does an acidic buffer work

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A
  • contains weak acid (HA) and salt of conjugate base (A-)(often from a soluble salt) in solution <– they don’t undergo any reactions to significantly alter concs.
  • considered as “reservoirs” ready to react with any added OH- or H+
24
Q

what happens when you add a strong acid to an acidic buffer

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A
  • conjugate base will react with H+ from strong acid to form weak acid HA
  • because H+ get absorbed by A- to form HA (weak acid only partially dissociates) not a lot of H+ is produced, pH remains constant
25
what happens when you add a strong base to an acidic buffer
- weak acid will give up H+ to transform base into water (H2O) and conjugate base (A-) - OH- is all consumed, pH doesn't really change
26
how does a basic buffer work
- contains aqueous solution of weak base with salt of a conjugate acid (ex. NH3 and NH4+) - these species act as reservoirs ready to react with H+ and OH-
27
what happens when you add a strong acid to a basic buffer (NH3, NH4+)
- H+ gets with NH3 forming weak acid NH4+ (weak base mops up excess H+)
28
what happens when you add a strong base to a basic buffer (NH3, NH4+)
- OH- gets with NH4+ forming NH3 and water, removing OH-
28
how to make a buffer
- depends on pKa and pKb and ratio of acid+salt or base+salt 1. start with acid/base with pKa/pKa close to needed pH 2. mix it with a solution of its salt or partially neutralize with strong acid/base
29
how does dilution affect pH, acid/base to salt concentration of buffering
- doesn't change pH - doesn't change acid/base to salt concentration - does change buffering capacity (amount of acid/base that can be absorbed while maintaining pH)
30
does temperature affect pH of a buffer
- affects pH of buffer (Ka and Kb values are changed)
31
what is a buffer
solutions that are resistant to changes in pH upon the addition of small amount of acid or alkali --> theres a limit to their capacity
32
what is the lewis definition of an acid and a base
- acid: electron pair acceptor - base: electron pair donor
33
bronsted lowry vs lewis acids and bases
b: more useful for acid-base reactions particularly in aq solutions l: includes a wider range of organic and inorganic species
34
what allows something to be a lewis acid but not a bronsted lowry acid
- can accept a pair of nonbonding electrons --> so typically e- decificient - compound of elements in group 13 and 15 - transition metal ions when combined with ligands (lewis bases)
35
what allows something to be a lewis base but not a bronsted lowry base
- ions or neutral compounds and must possess at least one pair of nonbonding e- - all ligands are lewis bases
36
nucleophile
- electron rich species(anion or neutral) that donate a lone pair to form a new covalent bond in a reaction
37
electrophiles
- electron deficient species(cation or neutral) that accepts a lone pair from another reactant to form new covalent bond
38
what is a coordination bond, how is it shown
- when one atom shares both its e- to form a covalent bond - curly arrow
39
hydrolysis
ionization of water that results from reaction with an ionic salt - affects pH of solution
40
hydrolysis of a strong acid and strong base + pH at equivalence point
- doesn't hydrolyse - pH at eqpt is always 7
41
hydrolysis of a weak acid and strong base + pH at equivalence point
HA+H2O ⇌ A- + H3O+ - hydrolysis of A- (when it reacts with water) determines pH at equivalence point - pH>7 as the hydrolysis produces basic salt
42
hydrolysis of a strong acid and weak base + pH at equivalence point
B + H2O ⇌ HB+ +OH- - hydrolysis of HB+ (when it reacts with water) determines pH at equivalence point - pH<7 as the hydrolysis produces acidic salt
43
end point vs equivalence point
visual point of neutralization vs when number of moles of A and B are equal
44
where is the equivalence point on a pH curve
point of inflection or middle of straight up section (SB +SA) middle of straight up section (WB+SA/WA+SB)
45
when is buffer formed in the titration WA+SB/SA+WB
- from the start point to the end of the buffer plateau
46
what is the half equivalence point
- stage of titration when half the amount of acid/base has been neutralized (when pKa = pH)
47
what is an indicator
- weak acid/base where the non-ionized acid has one colour and its conjugate base has another - changes colour reversibly according to pH of solution
48
titrant vs analyte
solution of the precisely known concentration vs. the solution of unknown concentration
49
rain is acidic/basic, why? how can you tell normal rain from acidic rain?
- acidic because as it falls, it dissolves CO2 from the atmosphere which is acidic - carbonic acid is weak, can only reach pH of 5.6 so acid rain is when pH<5.6 <-acidity is cause from more than CO2
50
what is acid deposition
process by which acidic particles/gases/precipitation leave the atmosphere and fall onto land (acid rain)
51
what is acidic rain caused by
- sulfur (dioxide and trioxide) dissolving in water <- from volcanoes + combustion of sulfur containing fuels - nitrogen (monoxide and dioxide) dissolving in water <- from action of some bacteria+internal combustion engines
52
how does acid rain affect marble and limestone statues
- marble/limestone are calcium carbonates so reaction is acid (from rain) + carbonate - in ionic equation, carbon dioxide and water is produced, salt gets washed away
53
methods to reduce emissions of sulfur oxides pre-combustion
- carpooling, using public transit - can be removed from coal and oil before they're combusted
54
methods to reduce emissions of sulfur oxides post-combustion
- flue gas desulfurization - flue gas is sprayed w/ wet slurry of lime --> sulfur oxide react with lime to form CaSO3 which can be removed as a solid
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