equilibria

Question 1

define conjugate acid-base pairs

Answer 1

species differ by one proton

Question 2

what is buffer solution

Answer 2

resists changes in pH when a small amount of acid or alkali is added to it

Question 3

define partition coefficient Kpc

Answer 3

the ratio of the concentration of solute in 2 immiscible solvents at equilibrium

Question 4

explain how is buffer solution prepared

Answer 4

establish equilibrium by weak acid/base, for conjugate acid-base pairs

Question 5

what is 1/2 equivalent point

Answer 5

when weak acid and its conjugate base has ratio 1:1

Question 6

what are feature of 1/2 equivalent point

Answer 6

1. pKa = pH
2. exactly half of [acid]
3. when the buffer is most effective

Question 7

how does polarity of solute affect the partition coefficient

Answer 7

1. if the solute is polar then more will dissolve in the water => [x] in water increase
2. if the solute is non-polar, then more dissolve in organic solvent

Question 8

explain how buffer control pH

Answer 8

1. establish equilibrium with conjugate acid-base pairs
2. if too much H+ then react with base to form conjugate acid
3. vice versa
   note: [HA] increase don’t change the pH as long as it doesn’t dissociate into [H+]