Simple memorisation is NOT the way to go!

Success in scholarship requires exhibiting deep understanding
Memorizing formulae that actually apply only to specific cases is not the way to succeed!

  • Solubility constant exampleMore
    Students may relate the solubility of A2B or AB2 ionic compounds to Ks by 
    Ks = 4 × s3

    NOT REALLY APPRECIATING
    how this is only true if the solid is dissolved in water with no other source of ions A and B AND
    how solubility is related to the concentrations of ions appearing in the Ks expression.
     
  • Acid-base equilibrium example More
    Ka = [H 3O+][A–]
    [HA]
    The equilibrium constant expression at the right pertains to ANY solution containing the acid, the conjugate base or a mixture of the two. 

    Ka = [H3O+]2
    c(HA)
    It is useless to memorise the formula at the right for calculating pH

    WITHOUT understanding that this applies only when
    [H3O+] = [A–] (never the case in a solution where the conjugate base is a major species)
    [HA] = c(HA) (not true for solutions where only the conjugate base as the major species)
     
Dr Sheila Woodgate
© The University of Auckland 2002