1. Chapter 8 Acids and Bases
8.7
Buffers

2. Buffers When an acid or base is added
to water, the pH changes drastically.
to a buffer solution, the pH is maintained; pH does not change.

3. Buffers
Buffers
resist changes in pH from the addition of acid or base.
in the body, absorb H3O+ or OH- from foods and cellular processes to maintain pH.
are important in the proper functioning of cells and blood.
in blood maintain a pH close to A change in the pH of the blood affects the uptake of oxygen and cellular processes.

4. Components of a Buffer A buffer solution
contains a combination of acid-base conjugate pairs.
may contain a weak acid and a salt of its conjugate base.
typically has equal concentrations of a weak acid and its salt.
may also contain a weak base and a salt of the conjugate acid.

5. Buffer Action In the acetic acid/acetate buffer with acetic acid
(CH3COOH) and sodium acetate (CH3COONa)
The salt produces acetate ions and sodium ions.
CH3COONa(aq) CH3COO-(aq) + Na+ (aq)
The salt is added to provide a higher concentration of the conjugate base CH3COO- than the weak acid alone.
CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq)
Large amount Large amount

6. Function of the Weak Acid in a Buffer
The function of the weak acid in a buffer is to neutralize a base. The acetate ion produced adds to the available acetate.
CH3COOH + OH− CH3COO− + H2O
acetic acid base acetate ion water
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

7. Function of the Conjugate Base
The function of the acetate ion CH3COO− is to neutralize H3O+ from acids. The acetic acid produced contributes to the available weak acid.
CH3COO− + H3O+ CH3COOH + H2O
acetate ion acid acetic acid water
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

8. Summary of Buffer Action
Buffer action occurs as
the weak acid in a buffer neutralizes base.
the conjugate base in the buffer neutralizes acid.
the pH of the solution is maintained.

9. Learning Check Which combination(s) make a buffer solution?
A. HCl and KCl
B. H2CO3 and NaHCO3
C. H3PO4 and NaCl
D. CH3COOH and CH3COOK

10. Solution B. H2CO3 + NaHCO3 A weak acid and its salt
D. CH3COOH + CH3COOK A weak acid and its salt.