Buffer Solutions

Question 1

Give the definition of a buffer solution.

Answer 1

• a buffer solution minimises the change in pH
• when acid or alkali is added in small amounts

Question 2

What are buffer solutions made of?

Answer 2

• a weak acid + one of its salts
• a weak base + one of its salts

Question 3

MAGIC SENTENCES
What happens if acid is added to a buffer solution?
What happens if alkali is added to a buffer solution?

Answer 3

If acid:
- equilibrium shifts to the left to minimise the change by using up most of the extra H+. There is lots of (name conjugate base) in the buffer solution to do this. So almost all of the extra H+ is removed and the pH hardly changes.

If alkali:
- the added OH- reacts with and hence removes the H+ making water. But equilibrium shifts to the right to minimise the change, so more (conjugate acid) dissociates replacing almost all of the H+ hence pH hardly changes.