Chapter 16: Reactions Between Acids and Bases Flashcards
titration: a procedure for the determination of the … of one substance by the addition of a measured amount of a second substance
quantity
analyte: substance whose concentration is
being determined
titrant is the substance added to
react with the analyte
(basic procedure for acid-base titrations) 1) a known volume of an acid of … is placed in a flask
unknown []
(basic procedure for acid-base titrations) 2) an indicator solution that changes color in a particular … is added to the acid
pH range
(basic procedure for acid-base titrations) 3) a standard solution of base is added until a … occurs, called the …
color change; endpoint
a titration curve is a graph of the pH of a solution as a function of the
amount of titrant that is added
equivalence point: point in the titration when exactly one mole of base has been added for
each mole of acid present in the sample
inflection point: point at which pH
changes most rapidly
the titration of a strong acid with a strong base shows a … in pH at the equivalence point
sharp change
the titration .., …, and … all influence the equivalence point volume
stoichiometry, concentrations, volumes
buffers are solutions that … when either OH- or H+ ions are added
resist changes in pH
strong acids and bases cannot be used as
buffers
buffered solutions contain either: a weak … and its … or a weak … and its …
acid; salt; base; salt
(buffers) keq for neutralization is … meaning that Keq is … and the reaction goes essentially to ..
1/Ka; large; completion
pH of buffer solutions is generally limited to the vicinity of the
pKa for the acid
buffers are most effective in the range of
pKa +- 1
to make an effective buffer, the concentrations of the weak acid and its conjugate base must be at least
100 times the Ka or Kb
most pH buffers are made from solutions with concentrations that range from
.1 to 1.0 M
concentrated buffers are generally more … than dilute buffers
effective
the effectiveness of a buffer is measured by
buffer capacity
buffer capacity= the amount of strong acid or base needed to change the pH of
one liter of buffer by one unit
acid/salt buffering pairs: salt will contain the …., and the cation of a
anion of the acid; strong base
base/salt buffering pairs: the salt will contain the cation of the …, and the anion of a …
base; strong acid
the amount of base needed to neutralize an acid depends only on the amount of
acid present, not whether it is strong or weak
the titration curves for all the acids are indistinguishable beyond the equivalence point since
excess OH- determines the pH of solution
the pH halfway to the equivalence point in the titration of a weak acid is equal to the
pKa
the pH at the equivalence point is not 7.0 unless
both the acid and the base are strong
indicator: substance that changes … to signal the end of a titration
color
an indicator should be chosen such that the … and … are the same
end point; equivalence point
indicators should have the following attributes:
change color … as a function of pH
color change should be …
should not … the system (should not consume a large amount of titrant/reactant)
abruptly; visible; perturb
indicators are … in which the acid is a different color from the conjugate base
weak acid-base conjugate pairs
HIn + H2O H3O+ + In-
Kin=
[H3O+][In-]/[HIn]
if pH < pKin, most of the indicator is in the .. form
if pH > pKin, most of the indicator is in the … form
acid; base
an indicator should be chosen to change color at or just beyond the
equivalence point
polyprotic acids provide more than one … when they ionize
proton
successive ionization constants for polyprotic acids get smaller often by a factor of
more than 1000
to estimate the pH of a polyprotic acid, treat as if you had a
mixture of weak acids
amphoteric species have the properties of both
acids and bases
to estimate the pH of a solution of an amphoteric substance, compare … and …. if Ka > Kb, the solution is …. if Kb > Ka, the solution is …
Ka; Kb; acidic; basic
the solubility of a salt of a weak acid increases with the addition of
acid
solubility of a precipitate increases in the presence of a
complexing agent
additive reactions –> … Ks to find overall equilibrium constants
multiply
