O - Equilibria (acid–base) *01 *02 Flashcards
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+