chem 2 exam 3 - titrations + buffers

K_ x K_ = K_w

K_a x K_b

K_w = ____ (numerical value)

1 × 10^-14

pK_w = ____

14

pK_ + pK_ = pK_w

pKa + pKb

how many H⁺ ions can a polyprotic acid donate?

2 or more

does polyprotic-ness have anything to do with an acid’s strength?

no

_______ acids ionize in subsequent steps

polyprotic

as a polyprotic acid ionizes more, what happens to its K_a?

decreases

does each ionization of a polyprotic acid contribute to total [H⁺]?

yes

what 2 elements make up a buffer?

weak acid, conjugate base

what is the purpose of buffers?

resist pH changes

products between weak acid (HA) and strong base (OH^-)

water, conjugate base

products between conjugate base (A^-) and strong acid (H₃O⁺)

water, weak acid

__ = pK_a + log ([conj. base] / [weak acid])

pH

if [weak acid] and [conj. base] are equal, ___ and ___ will also be equal

pH, pKa

2 ways to make buffers

weak acid/base and conjugate salt, weak acid/base and strong opposite

when there is a volume change in titration problem, what unit should be used in ICE tables?

moles

what can buffer effectiveness and buffer capacity tell you?

how much strong acid/base can be added before breaking buffer

how does a buffer change when it is broken? (reagent-wise)

no more weak acid or base present

how does a buffer change when it is broken? (pH change-wise)

large pH changes

most effective ratio of base to acid in a buffer

1:1

what ratio of base to acid / acid to base will completely break a buffer?

1:10

a _____ concentration buffer will be more effective

higher

how to find buffer range?

pKa +/- 1

buffer _____ and _____ are affected by the same factors (acid/base concentration + ratio) in the same way

capacity, effectiveness

when choosing a buffer, what should you be looking for (pH-pKa “relationship”)?

pKa is closest to desired buffer pH

at the _____ point, moles of weak reagent and strong titrant are equal

equivalence

how to find pH when there are reactants (H⁺ or OH^-) left at end of ICE table?

calculate pH/pOH from concentration present

in a strong acid-strong base titration, what is the equivalence point pH?

7

in a weak acid-strong base titration, is the equivalence point pH higher or lower than 7?

higher

in a weak base-strong acid titration, is the equivalence point pH higher or lower than 7?

lower

at the half-equivalence point, ___ = ___

pH = pKa

at the half-equivalence point, [___] = [___]

weak acid, weak base

the half-equivalence point is when half of the _____ is used up

weak acid/base