3.1.12 Acids and bases Flashcards
what is a Brønsted-Lowry acid?
a proton donor. e.g; Ammonium ions.
what is a Brønsted-Lowry base?
a proton acceptor. e.g; hydroxide ions
definition of a strong acid
an acid the completely dissociated to ions when in solution with pH 3-5
definition of a weak acid
an acid that only slightly dissociated when in solution with pH 0-1
what is a monoprotic acid?
an acid that donates one H+ from each molecule
what is a diprotic acid?
an acid that donates two H+ from each molecule
how do you find the pH of a strong acid?
pH = -log[H+]
how do you find the concentration of a strong acid?
[H+] = 10^-pH
how do you convert pKa into Ka?
Ka = 10^-pKa
what is the value of Kw?
10^-14
how do you find the concentration of a weak acid?
[HA] = [H+]^2
how do you find the concentration of a weak acid?
[HA] = [H+]^2/ Ka
what is the general equation for a weak acid before rearranging it?
Ka = [H+]^2/ [HA]
how do you work out the concentration of a weak base?
[H+] = Kw/ [OH-]
how do you work out the concentration of a strong base?
[OH-] = Kw/ [H+]
what is the equation for the ionic product of water?
Kw = [H+][OH-]
what affects the value of Kw?
the temperature
what is the reaction equation between a weak acid and a weak base?
HA H+ + A-
what is the equation for the reaction between a weak acid and a weak base?
Ka = [H+][A-]/ [HA]
what is the equation when there is excess HA (H+) in a mixture of a weak acid and weak base?
[H+] = Ka [HA]/ [A-]
what does [HA] refer to in the equation: Ka = [H+][A-]/ [HA]
if you are given the pH of a diprotic substance, what do you do?
half it
if you are given the conc of a diprotic substance, what do you do?
double it
what equation can be used for all aqueous solutions?
kW = [H+][OH-]
what equation can be used for all solutions containing a weak acid?
Ka = [H+][A-]/ [HA]
what equation can be used for a weak acid in water?
Ka = [H+]^2/ [HA]
how do you convert pKa into Ka?
Ka = 10^-pKa
what is the equation for excess [OH-] in a solution of a strong base and strong acid?
[H+] = Kw/ [OH-]
what is the equation for excess [H+] in a solution of a strong acid and strong base?
[H+] = n/ v
what does [H+] mean in Kw = [H+][OH-]
give simple steps about how to find the pH when HA is in excess in a solution of a weak acid and weak base
use [HA] and [A-] along with the Ka (normally given) to find [H+], then pH
[H+] = Ka [HA]/ [A-]
pH = -log[H+]
give simple steps about how to find the pH when A- is in excess in a solution of a weak acid and weak base
use Kw to find [H+], then pH
Kw = [H+]^2
pH = -log[H+]
give simple steps about how to find the pH when HA = A- in a solution of a weak acid and weak base
pKa = pH
find pKa
equation for the dissociation of water
H20 H+ + OH- (in eqm)
