L10 - electrolytes & buffers Flashcards
what can drugs be?
- weak electrolytes
- weak organic acids or bases
- strong electrolytes
- or their salts
what are buffers?
weak acidic or basic drugs + their salts
(they tie up any extra H+ released not allowing for change in pH)
use of buffers
- stop sudden changes in pH even when small concentrations of acid or base is added
- adjust pH of aq solutions for drugs that need stability
- control pH to lower drug degradation
what is the conjugate acid of a strong base?
weak acid
what is the conjugate base of a strong acid?
weak base
what is the conjugate base of a weak acid?
strong base
what is the conjugate acid of a weak base?
strong acid
where does the eqm lie when a weak acid reacts with water?
- left hand side
- conjugate base of a weak acid is a strong base
- so accepts H+ readily
- shifts eqm
- so A1 (weak acid) remains unionised
where does the eqm for a weak base + water lie?
- left hand side
- conjugate acid of a weak base is a strong acid
- so donates H+ readily
- shifts eqm
- so B1 (weak base) remains unionised
what is an electrolyte?
compound that is ionised in solution
what do electrolytes do?
yield ions (ionises to produce electrically charged atoms/ molecules) when dissolved in water so can conduct electric current through solution
strong electrolytes
strong acids or bases and their salts
weak electrolytes
weak acids or bases
what are non-electrolyte?
do not yield ions when dissolved in water so do not conduct an electric current through sol (e.g urea, sugars)
buffer capacity
- used to find better buffer
- size of resistance of a buffer to pH changes = buffer capacity
- ratio of strong acid/base to small change in pH when small amount added
