Acids and Bases: Buffer action

Question 1

What is a buffer solution?

Answer 1

A solution which resists change in pH when small amounts of acid/base/water are added

Question 2

What are the two types of buffers?

Answer 2

Acidic
Basic

Question 3

Where are buffers found?

Answer 3

Enzymes, cakes, shampoo

Question 4

How are acidic buffers formed from?

Answer 4

From a weak acid and its salt
(or excess amount of weak acid and a small amount of base)

Question 5

What happens when you add an acid to an acid buffer?

Answer 5

Concentration of H+ increases.
Most of the extra H+ ions combine with A- to form HA.
This shifts the equilibrium to the left so concentration H+ reduced to close to its original value.
So pH does not increase as much.

HA <-> H+ +A-

Question 6

What happens when you add a base to an acid buffer?

Answer 6

Concentration of OH- increases.
Most of the extra OH- ions react with H+ to form water.
This removes H+ ions from the solution so equilibrium shifts right to compensate by more HA dissociating.
So more H+ ions formed so pH does not change as much

Question 7

What happens when you add an acid to a base buffer?

Answer 7

Concentration of H+ increases.
This reacts with OH- to form water so equilibrium shifts to the right to counteract the decrease in OH-
So pH does not change much

Question 8

What happens when you add a base to a basic buffer?

Answer 8

Concentration of OH- increases.
This means equilibrium shifts to the left to counteract the increase in concentration of OH- ions - they react with the salt to form more base and H2O.
pH does not change by much