Buffer solutions
Definition, types of buffer solutions, mechanism of buffer action, and calculations using the Henderson-Hasselbalch equation.
What is Buffer solutions?
A solution that resists changes in pH when small amounts of acid or base are added.
Key formula / rule: Henderson-Hasselbalch Equation (for acidic buffers)
Key points
- Define buffer solutions and their types.
- Explain the mechanism of buffer action.
- Apply the Henderson-Hasselbalch equation to calculate buffer pH.
- Determine the buffer capacity and effective pH range.
Common exam trap
Confusing weak acids/bases with strong acids/bases when forming buffers.
Definitions
- Term
Buffer Solution
- Meaning
A solution that resists changes in pH when small amounts of acid or base are added.
- Term
Buffer Action
- Meaning
The ability of a buffer solution to maintain a relatively constant pH.
- Term
Buffer Capacity
- Meaning
The measure of the amount of acid or base a buffer solution can neutralize before its pH changes significantly.
- Term
pKa
- Meaning
The negative logarithm of the acid dissociation constant (Ka) of a weak acid; it indicates the strength of the acid.
Learning objectives
Define buffer solutions and their types.
Explain the mechanism of buffer action.
Apply the Henderson-Hasselbalch equation to calculate buffer pH.
Determine the buffer capacity and effective pH range.
Formulae
- Name
Henderson-Hasselbalch Equation (for acidic buffers)
- Note
pKa = -log(Ka)
- Expression
pH = pKa + log([conjugate base]/[weak acid])
- Name
Henderson-Hasselbalch Equation (for basic buffers)
- Note
pKb = -log(Kb)
- Expression
pOH = pKb + log([conjugate acid]/[weak base])
- Name
Relationship between pH and pOH
- Note
- Expression
pH + pOH = 14 (at 25°C)
Prerequisites
Acids and Bases
pH scale and calculations
Equilibrium concepts (Le Chatelier's principle)
Weak electrolytes and dissociation constants (Ka, Kb)
Common mistakes
Confusing weak acids/bases with strong acids/bases when forming buffers.
Incorrectly applying the Henderson-Hasselbalch equation, especially with stoichiometry.
Assuming buffer solutions can neutralize large amounts of added acid or base.
Keywords
Buffer solution
Weak acid
Conjugate base
Weak base
Conjugate acid
pH
pKa
Henderson-Hasselbalch equation
Buffer capacity
Buffer action
Practice preview
When a small amount of strong acid is added to an acetic acid/acetate buffer, which component primarily reacts with the added H+ ions?…
easy
An acidic buffer solution typically consists of:…
easy
Which of the following combinations will form a basic buffer solution?…
medium