5.1.3 - acids, bases and buffers

what is a brønsted-lowry acid

a species that donates a proton

what is a brønsted-lowry base

a species that accepts a proton

what is a conjugate acid-base pair

two species which differ by H+

what is a monobasic acid

release 1 H+ ion per molecule

what is a dibasic acid

releases 2 H+ ions per molecule

what is a tribasic acid

releases 3 H+ ions per molecule

what did lavoisier discover

that oxygen was responsible for combustion

what was lavoisier’s theory about acids

all acids contain oxygen

what was arrhenius’ theory

-acids donate protons and bases release hydroxide ions

-when an acid and base reacts they form salt and water

brønsted and lowry suggested that when we mix acids and water ____ ions are released

H+

brønsted and lowry suggested that when we mix bases and water ____ ions are released

OH-

what is the expression for Kw

Kw = [H+][OH-]

what can we simplify Kw to when referring to pure water and why

Kw = [H+]²

-pure water has an equal concentration of H+ and OH- ions

what is the value of Kw at 250

1\times10^{-14}

what is the equation for working out pH

pH = -log[H+]

what is the equation for working out [H+] if we are given pH

10^{-pH}

for strong acids what do we assume

we assume that the concentration of the acid is equal to the concentration of H+ ions because it fully dissociates

for strong bases what do we assume

we assume that the concentration of the base is equal to the concentration of H+ ions because it fully dissociates

how do we work out [H+] when we have Kw and [OH-]

\left\lbrack H^{+}\right\rbrack=\frac{K_{w}}{\left\lbrack OH^{-}\right\rbrack}

when do we use Ka

weak acids

what does Ka tell us

the extent of dicssociation

what do we assume when working with weak acids

-[HA(aq)]equilibrium = [HA(aq)]start

-[H+(aq)]=[A-(aq)]

what is the formula for Ka

Ka = [H+][A-] / [HA] or Ka = [H+]²

how do we calculate pka

-logKa

how do we calculate Ka from pka

10^{-pKa}