3.1.12 - acids and bases Flashcards
bronsted - lowry acid
proton donor
bronsted - lowry base
proton accepter
definition of pH
-log [H+]
reverse of the pH equation
H+ = 10 ^ -pH
what does amphoteric mean
a molecule that acts as an acid or base
what is a monoprotic acid
an acid with one hydrogen
what is a diprotic acid
an acid with two hydrogens
definition of a strong acid
acids which dissociate completely
definition of a weak acid
acids which only partially dissociate
how do you work out [H+] of a monoprotic or diprotic acid
monoprotic concentration = [H+]
diprotic concentration X 2 = [H+]
equation for Kw
[H+] [OH-]
effect on temp on the pH of water
pH decreases, Kw increases as equilibrium moves right to oppose the change
what is an indicator
a weak acid
methyl orange
works at pH 3.2- 4.4
red in acid
orange at midpoint
yellow in alkali
phenolphthalein
works at pH 8.2-10
colourless in acid
pink in alkali
equilibrium of pH
low pH - equilibrium shifts to the left, more acid than base
high pH - equilibrium shifts to the right, more base than acid
rules when choosing an indicator
sharp colour change
end point = equivalence point
distinct colour change
which indicator is used for which pH curve
strong acid + strong base = phenolphthalein
strong acid + weak base = methyl orange
weak acid + strong base = phenolphthalein
weak acid + weak base = no indicator
equivalence + steep pH values of SA + SB
E = 7
pH 3-9
equivalence + steep pH values of SA + WB
E = < 7
pH 4-7
equivalence + steep pH values of WA + SB
E = > 7
pH 7-9
what is a buffer solution
solution that resists change in pH when small amounts of acid/alkali are added
what are acidic buffers made from
a weak acid and a soluble salt of the acid.
excess of a weak acid and a strong alkali
what are basic buffers made from
weak base and a soluble salt of the weak base.
excess of a weak alkali and a strong acid
how do you find Ka
Ka= [H+] [A-] \ [HA]
