Chapter 2 Flashcards
properties of acids
dissolve in water to form solutions of pH<7
turn blue litmus indicator red
neutralise bases to salt + water
acids + carbonates form CO2 gas
monoprotic acids
donate 1 mole protons for every mole acid
e.g. hydrochloric acid, nitric acid
diprotic acid
donate 2 moles protons for every mole of acid
e.g. sulphuric
properties of bases
associated with hydroxide ion (OH-)
when soluble base dissolves in water the solution is pH>7
turn red litmus indicator blue
denature proteins
alkali
soluble base
Bronsted-Lowry theory of acids and bases
acid-base neutralisation
H3O+ acts as Bronsted acid and donates proton to OH- (Bronsted base)
Bronsted acid
proton donor
Bronsted base
proton acceptor
indicators
water-soluble dyes show colour change in diff pH solutions
pH
negative logarithm to base 10 of aqueous H+ conc. (H3O+)
mol dm-3
H conc. of monoprotic acid
conc. of acid itself
strong acids
fully ionised in aqueous solution
1 mole of hydrogen chloride and water = 1 mole of aqueous H+ (weak means less than 1mole aq H)
pH of strong acid only depends on its conc.
weak acids
partially ionised in aqueous solution
H3O+ conc. smaller than conc. of acid
equilibrium established between acid and ions
forms acid-base pair
forward reaction: acid donates proton to water (acts as base)
backward: acid donates proton to A- (base)
pH depends on conc. of acid and pKa
pKa
-log10Ka
strong bases
fully ionised so pH depends only on conc.
conc. OH = conc. base
weak bases
partially ionised
OH conc. < base conc.
e.g. aqueous ammonia
equilibrium shifted left
acid-base titrations
measure volumes of acid and base for neutralisation
plot volume against pH
neutralisation
acid + base —> salt
when point of equivalence for titration reached (H3O+ = OH-)
titration of strong acid with strong base
titration of strong acid and weak base
titration of weak acid with strong base
titration of weak acid with weak base
large pH change, small volumes, equivalence at pH7
base in excess, 1 acid drop before equivalence pH slightly >7, 1 acid drop after pH3
base in excess, end with acid in excess, large pH change near equivalence (11-7)
too gradual, conductivity low at start, improves as acid added, fully ionised salt
acidic buffer
weak acid with corresponding salt
pH<7
alkaline buffer
weak base with corresponding salt
pH>7
