Gen Chem II: Exam 2 Flashcards
pressure is proportional to —
molarity
for gases use K__
p
for aq use K__
c
both gases and aq use K__
c
when does Kp equal Kc?
if the amount of gas does not change in the reaction
what are the components present in an expression for K?
gaseous and aqueous
restores balance; if a system at equilibrium is disturbed, the disturbance causes the equilibrium position to shift
Le Chatelier’s Principle
which side will the reaction shift to?
the direction that minimizes the disturbance to achieve equilibrium again
what factors change the equilibrium position?
concentration
pressure/volume
temperature
If a chemical is removed, the system will act to produce more of it, making the reaction go to the —
left
If a chemical is present in excess, the system will act to consume it, making the reaction go to the —
right
only — and — will cause a shift
g and aq
decreased pressure means increased — (and vice versa)
volume
equilibrium shifts to the side with (more or less?) moles of gas when there is decreased pressure
more
equilibrium shifts to the side with (more or less?) moles of gas when there is increased pressure
less
adding an — has no effect on the equilibrium position, as long as the volume dos not change
inert gas
changes in — and — have no effect on K
pressure and volume
give the Arrhenius definition of acids and bases
acids produce H+ ions in water
bases produce OH- ions in water
give the Bronsted-Lowry definition of acids and bases
acids are proton donors and bases are proton acceptors
water is —
amphoteric
can be an acid or a base
amphoteric
any species that donates an electron pair to form a bond
a Lewis base
any species that accepts an electron pair to form a bond
a Lewis acid
molecules with incomplete octets of electrons
Lewis acids
a — acts as a Lewis acid when solvated by water
metal cation
water dissociates very slightly into ions in an equilibrium process known as —
autoioniaztion or self-ionization
same number of base and acid molecules
neutral
dissociates completely into ions in water
strong acid
dissociates slightly to form ions in water
a weak acid
a dilute solution of a strong acid contains no — molecules
HA
anions of carboxylic acids are – stabilized
resonance
the acid dissociation constant
Ka
stronger acids have a (smaller or larger) Ka?
larger
weaker acids have a (smaller or larger) Ka?
smaller
as the [HA] decreases, the % dissociation of the acid —
increases
an acid is an acid with more than one ionizable proton
polyprotic acid
— and — form a conjugate acid-base pair
Ka and Kb
a solution that minimizes changes in pH when acids or bases are added to it
acid-base buffer
what do acid-base buffers consist of?
appreciable quantities of conjugate acid-base pairs
more specifically, an acid-base buffer is composed of:
- acid and its conjugate base: HA & A-
2. base and its conjugate acid: B & BH+
a buffer woks through the —
common-ion effect
an application of Le Chatelier’s principle (for buffers)
common-ion effect
how does a buffer work?
the buffer components (HA & A-) are able to consume small amounts of added OH- or H3O+ by a shift in equilibrium position. This shift absorbs the change in [H3O+] or [OH-] and the pH changes only slightly
since Ka is a constant, the [H3O+] of the solution depends on —
the ration of buffer component concentrations
if the ratio [HA]/[A-] increases, [H3O+] —
increases
if the ratio [HA]/[A-] decreases, [H3O+] —
decreases
the pH range over which the buffer is effective
the buffer range
when are buffers most effective?
when the pH=pKa of the acid
buffers have a usable range within — of the pKa
+/- 1 pH unit
the ability of the buffer solution to resist changes in pH
buffer capacity
buffers with the greatest absolute concentration have the — buffer capacity
largest
when the strong base is added, the pH increases least for the —
most concentrated buffer
how do you prepare a buffer?
- choose a conjugate acid with a pKa near the pH range
- Mix the appropriate amounts of CA and CB to reach the desired pH (pH=pKa + log([CB]/[CA])
or - partially neutralize a weak acid or base with a strong acid or base, respectively.
