Lecture 6 Flashcards
What does the arrow tend to favour?
Weak acid and weak base
How does Ka differ between types of acids?
strong acids: large Ka value, will produce more acid molecules that completely dissociate
Weak acids: small Ka value, will produce less acid molecules that only partially dissociate
How does Pka differ between types of acids?
Strong acids: smaller value of Pka
Weak acids: larger value of Pka
What influences acidity?
- electronegativity increasing
- increasing bond energy
- inductive effects
- hybridisation effect
- delocalisation effects
How does pKa and Ka relate in terms of types of bases?
strong base: larger pKa values and smaller Ka values
weaker base: Smaller pKa values and larger Ka values
What influences basicity?
- decreasing electronegativity
- decreasing bond energy
- inductive effects
- hybridisation effect
- delocalisation effects
In terms of Henderson equation what does pKa mean for acids?
the pH at which it is exactly half dissociated
in terms of Henderson equation what does pKa mean for bases?
pKa of a base is the pH at which it is exactly half ionised.
What happens when we increase pH of strong acid (HE)?
increasing pH (more basic) pH>pKa = dissociated
What happens when we decrease pH of strong acid (HE)?
decreasing pH (more acidic) pH< pKa = undissociated
What happens when we increase pH of a weak base?
increasing pH, the base becomes less ionised as ph> pKa undissociated
What happens when we decrease pH of a weak base?
decreasing pH, the base becomes more ionised as pKa > pH so dissociates
What is a hydrolysis reaction?
reverse of neutralisation. Salt dissociates completely in
water to reform the acid and base (anion + cation)
What is the half equivalence point?
half of the total amount of base needed to neutralise
the acid has been added. pH = pKa of the weak acid
What is a dibasic acid?
has 2 ionisable groups
