Buffers

Question 1

What is a buffer?

Answer 1

solution that maintains a constant pH despite the addition of acid/base/water

Question 2

What is the pH of an acidic buffer?

Answer 2

below 7

Question 3

What is the pH of a basic buffer?

Answer 3

above 7

Question 4

What is an acidic buffer?

Answer 4

a weak acid and its salt

Question 5

How can an acidic buffer be made by adding acid to salt?

Answer 5

adding a solution of the salt to the weak acid (vice versa)

the salt dissociates completely and the acid slightly

Question 6

How can you make an acidic buffer by partial neutralisation?

Answer 6

by adding a strong base to the weak acid

• the salt is made as a product

Question 7

Where does equilibrium moves if H+ are added

Answer 7

H+ reacts with A-
eqm moves to left to decrease moles of H+

Question 8

Where does equilibrium moves if OH- ions are added?

Answer 8

alkali is added

they react with H+ forming H2O and eqm moves to right and more acid is dissociated to replace H+

Question 9

What is the equation for making a buffer using weak acid and its salt?

Answer 9

Ka = [H+] [A-]
————-
[HA]

A- = moles of salt
HA= moles of acid

Question 10

What effect does adding a strong acid have on a buffer

Answer 10

Increases moles of HA
Decreases moles of A-

Question 11

What effect does adding a strong base have on a buffer?

Answer 11

Decreases moles of HA
Increases moles of A-