L10 - electrolytes & buffers
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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