Chapter 21 - Buffers and neutralisation Flashcards
1
Q
What is a buffer?
A
A system that minimises pH changes on additon of small amounts of an acid or a base
2
Q
How is a buffer formed?
A
- Weak acid and its salt
- Excess of weak acid and a strong alkali
3
Q
How to calculate the pH of a buffer solution? (equations)
A
Ka = [A-][H+]/[HA] and pH = -log[H+]
4
Q
Explain the control of blood pH by the
carbonic acid–hydrogencarbonate buffer system
A
H2CO3 <=> H+ + HCO3-
- When acid is added, equ shifts to the left because there are more H+ that react with HCO3- and excess H+ needs to be removed
- When alkali is added, equ shifts to right because OH- reacts with H+. More H+ needs to be restored
5
Q
What indicator should be used for a weak acid/weak base titration?
A
No suitable indicator
6
Q
Define end point
A
The point during a titration when the indicator changes colour
7
Q
Define equivalence point
A
The point during a titration when [H+] = [OH-] (full neutralisation)
8
Q
What does the vertical section of a titration curve contain?
A
The equivalence point
