Oceans 3: Buffer Solutions

Question 1

Definition of buffer solution is

Answer 1

Solution that RESISTS changes in pH when SMALL amounts of acid or alkali are added

( pH does change, but not by much )

Question 2

How are acidic buffer solutions made ( 2 methods )

Answer 2

1. Weak acid + one of its salts
   ( HA and A- )
   Eg. Ethanoic acid + sodium ethanoate
2. Xs weak acid + strong alkali
   ( = mixture of HA and A- )

Question 3

How are basic buffer solutions made ( 2 methods )

Answer 3

1. Weak alkali + one of its salts
   ( Eg. Ammonia + ammonium chloride )
2. Xs weak alkali + strong acid

Question 4

What is the pH of acidic buffer solutions

Answer 4

pH < 7

Question 5

What is the pH of basic buffer solutions

Answer 5

pH > 7

Question 6

What can be noted about concentrations in acidic buffer solutions

Answer 6

[ acid ] & [ salt ]&raquo_space; [ H+]

Question 7

What can be noted about concentrations in basic buffer solutions

Answer 7

[ base ] & [ salt ]&raquo_space; [ OH- ]

Question 8

What 3 expressions are used to find the pH of an acidic buffer solution

Answer 8

1. Ka
   = [ salt = A ] [ H+] / [ acid = HA ]
2. [ H+] = Ka ( [ acid = HA ] / [ salt = A ] )
3. pH = -log [ H+ ]

Question 9

What is the effect of adding a LITTLE H+ or OH- to an acidic buffer

Answer 9

Ratio of acid / salt remains roughly constant as [ H+ ] is directly proportional to [ acid ] / [ salt ]