L8-electrolytes and bufffers

how to know if a drug is non-ionisable or not

for non ionisable drugs their pka’s are typically very low or very high i.e far outside the physiological range

what is a buffer

• a solution that can resist PH change upon the addition of an acidic or basic component

• its able to neutralise small amounts of added base or acid

• they have a working ph range and capacity which dictates how much base/acid can be neutralised before the ph begin to change

in order to do its role what must a buffer contain

it must contain a weak conjugate acid-base pair

so a a weak acid and its conjugate base ( strong base ) or a weak base and its conjugate acid ( a strong acid )

the conjugate base and acid are supplied by a salt

what is an electrolyte 

• an electrolyte is a substance that is ionised in a solution 

• electrolytes yield ions when dissolved in water and therefore can conduct an electric current through the solution 

differentiate between a strong electrolyte and a weak electrolyte

• a strong electrolyte is a substance that is completely ionised in solution i.e. strong acid/bases and their salts

• a weak electrolyte is a substance that is partially ionised in a solution i.e. weak acids/bases and their salts.

what is a nonelectrolyte

a substance that is not ionised in a solution and doesn’t conduct electricity

explain how -OH is removed when added 

the -OH reacts/ is removed by the weak acid in the buffer and it forms undissociated water

explain how the +H3O/acid is removed by a buffer system when its added

the +H3O/acid reacts with the ions from the negative ions/ strong base contained in the salt.

explain the common ion effect

• when a buffer contains a weak acid and a salt containing its conjugate base and they both dissociate to give the same conjugate/strong base

• this means that in the system containing the weak acid the equilibrium will shit to the reactants/away from the conjugate base and towards the reactants

• so the ionisation of the weak acid is repressed

what is the Henderson-Hasselbalch equation for buffers

the only difference is to remember that depending on if its a weak base or acid the conjugate base or acid will be represented by a salt

what is buffer capacity

the effectiveness of a buffer in reducing changes in PH