O - Buffers

Question 1

what is a buffer?

Answer 1

solutiuon that minimises pH change when small amounts of acid or alkali are added to a solution

Question 2

hoe does a buffer work?

Answer 2

by mopping up H+(aq) or OH-(aq) ions

Question 3

what are buffer solutions usually made from?

Answer 3

weak acid and one salt or a weak base and one of its salts

e.g ethanoic acid and sodium ethanoate

Question 4

what is the first assumption we can make from the action of buffer solutions?

Answer 4

all A- ions come from the salt
[A-(aq)] = [salt]

Question 5

what is the second assumption we can make from buffer solutions?

Answer 5

almost all the HA molecules put into the buffer are unchanged
[HA(aq)] = [acid]

Question 6

using the assumptions how do you can calculate Ka?

Answer 6

Ka = H+ x( [salt] / [acid] )

Question 7

what does Ka supply?

Answer 7

a rough value for the pH of the buffer solution

usually between 1x10-4 to 1x10-9