Buffer

Question 1

Definition of buffer

Answer 1

Solution that can resist changes in ph when a small, amount of acid or base is added

Question 2

Acidic buffer

Answer 2

Made of weak acid and a soluble salt of that acid
Maintains ph below 7

Question 3

Acidic buffer example

Answer 3

HA is weak acid and NaA is salt of that acid
HA<->H+ + A-
NaA<->Na+ + A-
If extra h+ is added it will react with a- to form ha so [h+] remains constant
If extra oh- is added they will combine with h+ to make h2o
Then more ha will dissociate to replace h+ ions and [h+] will stay constant

Question 4

basic buffer

Answer 4

Made of weak base and soluble salt of that base
Maintains ph above 7

Question 5

Example of basic buffer

Answer 5

Nh3 is weak base and nh4cl is salt of that base
Extra h+ added they will combine with nh3 to make nh4+ so [h+] will remain constant
If extra base oh- added will combine with nh4+ to form nh3 and h20 this maintains [h+] at a constant level

Question 6

What is each value in a equation

Answer 6

Ka=[h+][a-]/[ha]
Buffer conc = [ha]
Salt conc = [a-]

Question 7

Buffer calc by neutralisation

Answer 7

Find moles of both ha and salt
Use ice box to find end mole
Sub in values to ka

Question 8

Special situation
Half neutralisation point

Answer 8

If at ice box end moles are equal
Ka=[h+]

Question 9

Definition half neutralisation point

Answer 9

The point at which enough base has been added to neutralise exactly half of the acid
AT HALF EQUIVALENCE POUNT

Question 10

when a substance is added to a buffer

Answer 10

Find mole of substance added = x
If h+
It will combine with a- to give ha
So value of a- will go down by x and value of ha will go up by x
If oh-
Will combine with h+ to give h2o
So more ha will dissociate to replace h+
So ha goes down by x
A- increases by x