Acid Base Equilibrium Flashcards
define ‘acid’
proton donator
define ‘base’
proton acceptor
define pH
-log(H+)
define ‘strong acids’
acids that completely dissociate
how to calculate [H+]
10^(-pH)
define ‘ionic product of water (Kw)’
Kw= [H+][OH-}
what type of reaction is phenolphthalein best for?
weak acid and strong base reactions
how to calculate the pH of buffers when given values of HA and A- and NaOH is added
rearrange the Ka equation so its equal to [H+]
calculate the concs of HA and A- by dividing equilibrium moles by total volume
plug them into this new equation
and plug new H+ into pH equation
What makes an indicator suitable for a reaction
If the PH range so the colour change occurs at the during the vertical region
how to calculate pH of buffers when its just the values of HA and A-
rearrange the Ka equation so its equal to [H+]
calculate moles of HA and A-
you can plug these values straight into the equations as they will have the same total volume
plug this value into pH equation
why are the enthalpy changes of neutralisation for strong and weak acids different?
Weak acids have a less exothermic enthalpy change of neutralisation because energy is absorbed to ionise the acid and break the bond to the hydrogen in the un-dissociated acid.
why is the equivalence point of weak acid-strong base reaction greater than 7?
the A- are present
A- react with water
these creates an excess of OH- ions
why does the pH not increase as much when a weak acid is diluted
because degree of dissociation increases and equilibrium shifts to the right so the pH is kept lower as there is a higher amount of H+ present
how to work out Ka from a titration curve
pH=pKa at half equivalence point
and at half equivalence point A- is equal to H+ so Ka is equal to H+
