O - Equilibria (acid–base) *01 *02
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (24 张)
what are acids?
proton donors they release H+ ions when they are mixed with water
Why would you never get H+ ions by themselves in water?
because they are always combined with water HA (aq) + H2O (l) —> H3O+ (aq) + A- (aq)
What is a base?
proton acceptors when in solution they grab H+ ions from water molecules B (aq) + H2O (l) —> BH+ (aq) + OH- (aq)
What is a strong acid?
completely dissociate in water HCl (g) + water —> H+ (aq) + Cl- (aq) (reversible but equilibrium lies very far to the right)
What is a strong base?
completely dissociate in water NaOH (s) + water —> Na+ (aq) + OH- (aq) (reversible but equilibrium lies very far to the right)
What is a weak acid?
only dissociate slightly in water CH3COOH (aq) + water < —> CH3COO- (aq) + H+ (aq) an equilibrium is set up which lies well over to the left
What is a weak base?
only dissociates slightly in water
What happens when acids and bases react?
protons are transferred base accepts protons, acid gets rid of them HA (aq) + B (aq) < —-> BH+ (aq) + A- (aq)
base + acid reaction [HA (aq) + B (aq) < —> BH+ (aq) + A- (aq)] - what would shift equilibrium right?
adding more HA or B
base + acid reaction [HA (aq) + B (aq) < —-> BH+ (aq) + A- (aq)] - what would shift equilibrium left?
adding more BH+ or A-
What happens when an acid is added to water?
water acts as a base HA (aq) + H2O (l) < —> H3O+ (aq) + A- (aq) for weak acids equilibrium left for stong acids equilibrium right
Identify the acid and base in this reaction HCl (aq) + NH3 (aq) —> Cl- (aq) + NH4+ (aq)
HCl = acid - it donates a proton to NH3 so it becomes NH4+ NH3 = base - it accepts a proton from HCl to become NH4+
What do acids and bases form?
Conjugate pairs
What are conjugate pairs?
eg. HA + H2O < —> H3O+ + A- acid 1 base 2 acid 2 base 1 HA and A- are conjugate pairs • in the forward reaction HA donates a proton to form A- • in the reverse reaction A- acts as a base and accepts a proton from the H3O+ to form HA H2O and H3O+ is also a conjugate pair HA < —> H+ + A- and H+ + H2O < –> H3O+
Identify the conjugate pairs HCl (aq) + H2O (l) < —-> H3O+ (aq) + Cl- (aq)
HCl (aq) + H2O (l) < —-> H3O+ (aq) + Cl- (aq) acid 1 base 2 acid 2 base 1 HCl and Cl- H2O and H3O+
a neutral solution is one in which…..
[H+] = [OH-]
what does the pH scale measure?
the hydrogen ion concentration
How can you work out pH
pH = -log10 [H+]
what are monoprotic acids?
strong acids (ionise fully) each mole of acid produces one mole of hydrogen ions [H+] = [acid] eg. 0.1 mol dm^-3 HCl [H+] = 0.1 mol dm^-3 so pH = -log10 [H+]
How do you work out [H+] from pH?
[H+] = 10^-pH
Ionic product of water =
Kw = [H+] [OH-] Kw is always 1.00 x 10^-14 at 298K
Where does equilibrium lies - when water dissociates H2O < —-> H+ + OH-
far to the left
in pure water relationship between [H+] and [OH-]
[H+] = [OH-] so Kw = [H+]^2
How do you find pH of a strong base
Kw = [H+] [OH-] if conc. of base = 0.02mol dm^-3, [OH-] = 0.02mol dm^-3 [H+] = Kw / [OH-] pH = -log10[H+]