A2: Buffers

Question 1

What does a buffer solution contain?

Answer 1

Weak acid (HA) and its conjugate base (A-)

Question 2

What is the role of a buffer solution?

Answer 2

Aims to minimise pH changes when a small amount of acid or alkali is added

Question 3

How can a buffer be prepared?

Answer 3

Mixing a weak acid and its salt, or partial neutralisation of a weak acid (excess of the acid)

Question 4

How does a buffer control pH?

Answer 4

1) contains reservoirs of HA and A-
2) equilibrium HA <–> H+ +A- is present
3) acid added, H+ + A- -> HA, shifting the position of equilibrium to the left
4) alkali added, OH- + H+ -> H2O, shifting p.o equilibrium to the right