Buffers and Buffer Capacity (CH 8) Flashcards
define buffers
compounds/mixtures of compounds that, by their presence in solution, resist changes in pH upon the addition of small quantities of acid or base
give a specific example of a buffer solution
acetic acid and sodium acetate
define buffer capacity
the magnitude of resistance of a buffer to pH changes
when preparing a pharmaceutical buffer solution, what should the relationship be between the pka and pH of the weak acid?
they should be around the same value
state the buffer equation for a weak base and its salt
pH = pkw-pkb + log [base]/[salt]
what does buffer capacity mean?
the magnitude of the resistance of a buffer to pH changes
in an equimolar solution of acetic acid and sodium acetate, the more moles of NaOH added, the ___ the pH and the _____ the buffer capacity
the higher the pH and the less the buffer capacity
give the buffer equation for a weak acid and its salt
pH = pKa + log [salt]/[acid]
in the preparation of pharmaceutical buffer solutions, you should select what kind of weak acid?
where the pKa is ~ the pH
MAXIMUM BUFFER CAPACITY OCCURS WHERE
_____=_____
pH = pKa
give the maximum buffer capacity formula
Bmax=0.576C
name the “in vivo” biological buffer systems
blood
lacrimal fluid (tears)
urine
name 2 pharmaceutical buffers
parenteral solutions and ophthalmic solutions
what is the physiological pH
7.4
in a hypertonic solution, what happens to RBC?
they crenate
an a hypotonic solution, what happens to RBC?
hemolysis
2% NaCl is a ___ solution
hypertonic
0.2%NaCl is a ______ solution
hypotonic
0.9% NaCl is a ___ solution
isotonic
what are the class I methods of adjusting tonicity
cyroscopic method
sodium chloride equivalent method
what are the class II methods of adjusting tonicity
White-vincent method
Sprowls method
the white vincent method uses what values?
isotonic solution values
what can be used to adjust tonicity?
NaCl and dextrose
buffer capcity depends on what 2 things?
the values of the [salt]/[acid] ration
the magnitude of the individual concentrations of the buffer components
