Study Set Content:
pH =
pKa + log [salt]/
[acid]
dissociation exponent
pKa
The buffer equation is important in
the preparation of buffered
pharmaceutical solutions, it is
satisfactory for calculations within
the pH of
4 to 10
The buffer capacity on the value of
the ratio ([salt[/[acid]), increasing as
the ratio approaches unity, and the
magnitude of the individual
concentrations, the buffer becoming
more efficient as the salt and acid
concentrations are
increased
The smaller the pH change with the addition of a given amount of acid or base, the greater the (blank) of the system
buffer capacity
[OH] =
Kb [base]/[salt]
addition of neutral salts such as
sodium chloride affect pH of a buffer
solution by altering
ionic strength
ionic strength affects
ionization
constants,
activity of ionized species
(salt form) of the buffer, and activity
of hydronium ion which alters pH of
solution
ionization
constants,
affects Ka
, Kb
, and Kw
Temperature
Buffer shows it greatest efficiency when
pH=pKa
An indicator exhibits its middle tint when
base/acid=1
The most efficient indicator range, corresponding to the effective bufffer interval, about 2 pH units, that is,
pKin +-1
Some medicinal solutions and
pharmaceutical vehicles, however, to
which no buffers have been added
are buffered by the presence of the
drug itself and can withstand the
addition of an indicator without a
significant change in
pH
buffer efficiency, buffer index, buffer
value
Buffer capacity
Buffer Capacity equation
Van Slyke Equation
define as the ratio of the increment
of strong base (or acid) to the small change in pH brought about by this
addition
Buffer capacity
∆ (delta)
finite change
small increment in gram
equivalents of strong base added to
the buffer solution to produce a pH
change in ∆pH
∆B
The buffer capacity of a solution has
a value of 1 when addition of 1 g Eq
of strong base (or acid) to 1 liter of
the buffer solution results in a
change of
1 pH unit
