acids + bases Flashcards
Ka =
[H+] [A-] / [HA]
Kc =
[products] / [reactants]
Gibbs free energy (Δ G) =
= Δ H − T Δ S
pH =
-log[H+]
[H+] =
10 -pH
ionic product of water (KW) at 298K
1x10-14 mol2dm-6
why is [H+] larger at higher temps (for water)
because temp increase favours endothermic reaction, shifting equilibrium to right ∴ KW increases ∴ [H+] increases
how can you tell if something is a catalyst
it is expressed in the rate equation but not in the stoichiometric equation
assumptions made about weak acids (2)
1) [HA] at equ. ≈ [HA] initial
2) [A-] ≈ [H+] because [H+] from water is negligable
eq. ionic product of water (Kw)
[H+][OH-]
eq. pH of water
[H+] = √Kw
eq. pH of diluted strong acid
[H+] x (old vol / new vol) —> -log(ans)
effect of temperature on pH of water
temp increase = equilibrium shift to the right
[H+] and [OH-] INCREASE
Kw increase, pH decrease
effect of temp on neutrality of water
no effect, as [H+] = {OH-] still
eq. for calculating pH of a strong base
[H+] = Kw/ [OH-]
eq. Ka of weak acids in aqueous solution with nothing else added
Ka = [H+]² / [HA]
bronsted-lowrey acid
a proton donor
bronsted-lowrey base
a proton acceptor
monobasic acid
and eg.
an acid that releases 1 H+ ion per molecule
eg. = HCl
dibasic acid
and eg.
an acid which releases 2 H+ ions per molecules
eg. H2SO4
acid + metal =
salt and hydrogen
acid + carbonate =
salt + water + CO2
acid + base =
salt + water
conjugate acid-base pair
2 species which can be converted Ito each other by the transfer of a proton
2 ways of making an acidic buffer
1) weak acid and one of its salts
2) mix of excess weak acid and strong base
2 ways of making an basic buffer
1) weak base and one of its salts
2) mixture of an excess of weak base and strong
pH blood plasma has to be
7.35-7.45
buffer system in the body
carbonic acid-hydrogen carbonate
equilibrium for body buffer system
H2CO3 ⇌ H+ + HCO3
what happens to body equilibrium when H+ added
[H+] increases
[H+] reacts with conjugate base HCO3-
eq. moves left, making more H2CO3, removing H+
what happens to body equilibrium when OH- added
[OH-] increases
small conc go H+ react w OH-
H2CO3 dissociates to restore H+ ions
eq. shifts right, making more HCO3- and H+
how does body prevent build up of H2CO3
converts it to CO2 which is exhaled by lungs
weak acid
do not fully dissociate
derivatives of carboxylic acid (4)
- ester
- acyl chloride
- acid anhydride
- amide
methyl orange can always be used with….
strong acid
phenolphalien can always be used with…
strong base
pH weak acid
[H+] = √ KA x [HA]
d. indicator
weak acids which have a different colour to their conjugate base
relationship between PKa and Ka
PKa = -log(Ka)
equation for: pH of mixture when H+ is in excess
weak acid
= H+ = Ka x [HA]/[A-]
equation for: pH of mixture when OH- is in excess
H+ = KW/[OH-]
equation for: pH of mixture when H+ is in excess
strong acid
pH = -log(H+)
acid + metal ->
salt + hydrogen
acid + carbonate ->
salt + CO2 + H2O
acid + base ->
salt + water
acid + alkali ->
salt + water
the bigger the value of Ka the further the eq is to the….
RIGHT
stronger acids have …
larger Ka , smaller pKA
what is pKa used for?
comparing
equivalence point
the point in a titration where a volume of one solution has reacted exactly with a volume of the other
end point of titration
indicator contains equal vols of HA and A-
