21.1 Buffer Solutions

Question 1

What is a buffer solution?

Answer 1

System

which minimises pH changes

on addition of small amounts of acid/base

Question 2

What are the components of a buffer?

Answer 2

1. Weak acid
2. It’s conjugate base

Question 3

In which 2 ways can you prepare a weak acid buffer solution?

Answer 3

1. Weak acid + salt
2. Partial neutralisation of weak acid

Question 4

How can you prepare a weak acid buffer solution from a weak acid and it’s salt?

Answer 4

1. Obtain weak acid
2. Obtain conjugate base from salt of weak acid.

CH₃COONa ⟶ CH₃COO-_(aq) + Na⁺_(aq)

Question 5

How can you prepare a weak acid buffer solution from partial neutralisation?

Answer 5

1. Obtain weak acid
2. Partially neutralise using base to obtain salt, which can be used as base.

AH + NaOH ⟶ ANa + H₂O (partial)

Question 6

How does adding small amounts of acid affect the equilibrium of a weak acid buffer solution?

Answer 6

[H⁺] increases

more H⁺ react with conjugate base, A^-

equilibrium shifts to left (∵ backward reaction favoured)

Question 7

How does adding small amounts of alkali affect the equilibrium of a weak acid buffer solution?

Answer 7

[OH^-_(aq)] increases

OH^- react with H⁺

equilibrium shifts to right (∵ forward reaction favoured)

to restore [H⁺_(aq)]

Question 8

How can you find the pH of a solution using the acid dissociation constant?

Answer 8