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chemistry > 21 - further aspects of equilibria > Flashcards

21 - further aspects of equilibria Flashcards

(51 cards)

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1
Q

Bronsted Lowry acids

A

proton donors

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2
Q

Bronsted Lowry bases

A

proton acceptors

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3
Q

equilibrium

A

product to reactants at same rate as reactants to products

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4
Q

conjugate pair

A

an acid base pair on each side of an acid base equilibrium equation that are related to each other by the difference of a hydrogen ion

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5
Q

HCl + H2O <=> H3O+ + Cl-

A

. H2O and H3O+
. base and acid
. thus conjugate pair

. HCl and Cl-
. acid and base
. thus conjugate pair

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6
Q

NH3 + H2O<=> NH4+ + OH-

A

. NH3 and NH4+
. base and acid
. thus conjugate pair

. H2O and OH-
. acid and base
. thus conjugate pair

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7
Q

Kw

A

ionic product of water

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8
Q

ionic product of water

A

the equilibrium constant for the ionisation of water

Kw = [H+] [OH-] = [H+]²

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9
Q

Kw value at 298K

A

1* 10^-14
mol² dm^-6

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10
Q

water equilibrium reaction

A

H2O + H2O <=> H3O+ + OH-
simplified
H20 <=> H+ + OH-

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11
Q

Kc of H20 <=> H+ + OH-

A

Kc = [H+] [OH-] / [H2O]

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12
Q

pH formula

A

pH = -log10 [H+]

. negative sign to make pH values positive
. logarithms to the base 10
. equation used to convert between pH and H+ concentration

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13
Q

monobasic acids

A

an acid that can only donate one hydrogen ion per molecule in an acid-base reaction or when dissolved in water

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14
Q

strong monobasic acids

A

completely ionised in solution, eg. HCl

[H+ in solution] = [of acid]

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15
Q

strong bases

A

ionise completely in solution

for pH calculation use Kw = [H+] [OH-]

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16
Q

Ka

A

acid dissociation constant

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17
Q

acid dissociation constant

A

an equilibrium constant for the dissociation of a weak acid

Ka = [H+] [A-] / [HA]
At 298K, Ka = 1.74*10^-5

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18
Q

At 298K, Ka

A

= 1.74*10^-5
mol dm-3

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19
Q

high Ka value

A

. eq pos to right
. acid almost completely ionised

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20
Q

low Ka value

A

. eq pos to left
. acid only slightly ionised

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21
Q

pKa values

Study These Flashcards
A

values of Ka expresded as a logarithm to the base 10

pKa = - log10Ka

22
Q

more positive value of pKa

Study These Flashcards
A

less strongly acidic acid

23
Q

p infront of symbol

Study These Flashcards
A

-log10 multiplied by symbol

24
Q

Ka of weak acid

Study These Flashcards
A

. [H+] = [A-]
. Ka = [H+]² / [HA]

assumptions
. ignore concentration of H+ions produced by ionisation of water molecules
. small ionisation of weak acid
. concentrations of undissociated HA molecules ≈ original acid

25
pH of weak acid
. acid concentration . Ka value of acid
26
buffer solution
a solution that minimises changes pH when moderate amounts of acid or base are added
27
buffer solution is
. weak acid and conjugate base . weak base and conjugate acid
28
weak acid + salt
eg: CH3COOH + CH3COONa . different proportions = different different pH buffers . CH3COOH mostly unionised . CH3COONa fully ionised thus high CH3COOH and CH3COO- concentrations THESE ARE RESERVE SUPPLIES OF ACID AND CONJUNGATE BASE
29
pH of buffer solution depends on
ration of concentration of acid to concentratation of conjugate base less ratio change = less pH change
30
weak acid + salt (changing H+ ion numbers)
CH3COOH <=> H+ + CH3COO- MORE H+ . eq pos to left, . reserve ensures no change in CH3COO- . reserve ensures no change in CH3COOH . no pH change MORE OH- . form water, less H+ . eq pos to right . CH3COOH ionise . reserve ensures no change in CH3COO- . reserve ensures no change in CH3COOH . no pH change
31
rainwater
.pH = 5.7 .CO2 dissolves in water to form weak carbonic acid H2CO3 . H2CO3 and HCO3- acid as buffer solution . in polluted areas with acidic oxides, pH is not constant
32
weak base + salt
eg: NH3 + H2O <=> NH4+ + OH- NH4Cl <=> NH4+ + Cl-
33
pH of buffer solution
[H+] = Ka * [acid] / [salt] pH = Ka + log10 [acid] / [salt]
34
human blood
. pH = 7.35 to 7.45 buffers: . HCO3- . haemoglobin . plasma proteins . H2PO4- dihydrogenphosphate . HPO4- hydrogen phosphate CO2 + H2O <=> H+ + HCO3- catalyst = carbonic anhydrase
35
if [H+] concentration in human blood increases
CO2 + H2O <=> H+ + HCO3- . eq pos to left . H+ and HCO3- combines . reducing H+ concentration
36
if [H+] concentration in human blood decreases
CO2 + H2O <=> H+ + HCO3- . eq pos to right . H+ and HCO3- formed . increasing H+ concentration
37
solubility
the number of grams/moles of compound needed to saturate 100g/1kg of water at a given temperature
38
saturated solution
solution with cannot dissolve any more solute
39
undissolved ionic compound + saturated solution of its ions
equilibrium established
40
Ksp
solubility product
41
solubility product
Ksp = the product of the concentrations of each ion in a saturated solution of a sparingly soluble salt 298K, raised to the power of their relative concentration ONLY APPLIES TO SLIGHTLY SOLUBLE IONIC COMPOUNDS eg: Fe2S3 <=> 2Fe3+ + 3S2- Ksp)= [Fe3+]² [S2-]³
42
bigger Ksp value
bigger solublilty of salt
43
precipitation from Ksp
. find Ksp if product if ion concentrations is: . > Ksp, ppt . < Ksp, no ppt ONLY FOR SLIGHTLY SOLUBLE
44
soluble salts
. group one elements . nitrates . ammonium salts . many sulfates . halides (except lead and silver)
45
common ion effect
the reduction if the solubility of a dissolved salt by adding a compound that has an ion in common with the dissolved salt OFTEN RESULTS IN PPT eg. NaCl + PbCl2
46
immiscible solvents
solvents that do not dissolve in each other
47
Kpc
partition coefficient
48
partition coefficient
Kpc = the ratio of the concentrations of a solute in two immiscible solvents in contact with each other when equilibrium has been established Kpc = [org. solvent] / [aq]
49
ammonia Kpc
. more polar (stronger H bondss in water) . more soluble in water . less soluble in organic solvents . Kpc < 1
50
iodine dissolving in water
I2 + H2O <=> IO- + I- + 2H+ .eq pos to left
51
chromatography
. more soluble . faster rate of movement

chemistry (22 decks)

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