Chapter 14 - Acid and Base titration

what is a buffer

a solution containing considerable parts of a weak acid and it’s conjugate base

how does adding a strong acid or strong base affect the pH of a buffer

it is strongly resistent to changes

what is the pH of a buffer close to

the pKa of the weak acid

do buffers go to equilibrium or completion

completion

the equilibrium constant of a buffer should be _________

very large

what affect to H+ and OH- ions have on the pH of a buffer

very little

with a buffer, what kind of diagram do you use

BCA (before change after)

[HB]/[B-] = what?

mols hb/mols b-

how to calculate pH of a buffer system

H.H equation

what are the two factors that the pH of a buffer depend on?

acid equailibrium constant of the weak acid and the ratio of concentrations/amounts of HB and B- (think H.H equation)

what changes when a buffer system has a strong acid or strong base added to it?

pH changes very slightly, the ratio of mols HB/mols B- changes

what is buffer capacity

the amount of OH- or H+ ions that can be absorbed without a big change in pH

How do you pick an indicator for an acid-base rxn?

pick an indicator with an end point that aligns with the pH of the acids/bases equivilance point

what is the equivilance point?

the point at which reaction is complete, equal amounts of acid and base have reacted

what does it mean if [HIn]/[In-] is >= 10? (in means indicator)

the acid color comes through

what does it mean if [HIn]/[In-] is <= 0.1? (in means indicator)

the base color comes through

what does it mean if [HIn]/[In-] is ~~ 1? (in means indicator)

the color is an intermediate between the two species (I.E. green)

what equation to use to get concentration of indicators?

Ka = [H+][In-]/[HIn]

what happens if [in]~~ [HIn]

the solution will be an intermediate green color

for a methyl red indicator, what color indicates low pH

red

for a methyl red indicator, what color indicates high pH

yellow

for a bromythymol blue indicator, what color indicates low pH

yellow

for a bromythymol blue indicator, what color indicates high pH

blue

for a phenolphthalein indicator, what color indicates low pH

colorless

for a phenolphthalein indicator, what color indicates high pH

bright pink

what does a high Kc indicate about the reaction?

that it goes to completion

on a graph, where is the equivilance point?

the steepest part of the graph

how to tell on a acid-base titration graph if the acid/base is strong or weak

very low initial pH = strong acid

what does it mean if the pH = 7 at the equivilance point

strong acid and strong base are reacting

how to find k for the reverse of a reaction

1/(kb)

what does it mean if on a acid-base titration graph the initial pH is between 2-4

weak acid

what is true on a acid-base titration graph halfway to the equivilance point

pH = pKa

what does it mean if the starting pH in an acid-base titration is 10-12

weak base

what is the net ionic equation for a weak acid in water

HB + H2O >< B- + H3O+

what is the net ionic equation for a weak base in water

B- + H2O <> HB + OH-

what is the net ionic equation for a weak acid and a strong base

HB + OH- => B- + H2O

what is the net ionic equation for a strong acid and a weak base

H+ + B- => HB

what is the net ionic equation for a strong acid and a strong base?

H+ + OH- => H2O

the k value of a weak acid and strong base will be ______

high

the k value of a strong acid and a strong base will be _____

high

what kind of chart do you use if a weak acid is in water

ICE

in an ICE diagram, what should you use?

molarity, -x and +x

in a BCA chart, what should you use?

LF, mols

for a weak base in water, what chart should you use?

ICE

in a weak acid + strong base, what chart should you use?

BCA

for a strong acid + weak base, what chart should you use

BCA

for a strong acid and strong base, what chart should you use?

BCA