How to determine Acidic and Alkaline Buffer Solutions - Ionic Equilibria
In this video we want to discuss Buffer Solutions.
Definiton of a Buffer Solution
We know that a buffer solution is one that maintains pH when small amounts of H+ or OH- is added to it.
This means that inside this buffer, the following components must be present:
- an acid to remove OH-
- a base to remove H+
This mixture of acid and base must be of a conjugate acid-base pair, otherwise the acid and base will neutralise each other in the same solution.
Acidic Buffer
An acidic buffer is a mixture of weak acid and salt of conjugate base.
An example is a mixture of CH3COOH and CH3COONa.
For this mixture of conjugate acid-base pair:
- CH3COOH is the acid that removes OH-
- CH3COO- is the base that removes H+
We can show how H+ and OH- is removed via neutralisation reactions:
Since H+ and OH- is removed, therefore pH is maintained.
Alkaline Buffer
An alkaline buffer is a mixture of weak base and salt of conjugate acid.
An example is a mixture of NH3 and NH4Cl.
For this mixture of conjugate acid-base pair:
- NH4+ is the acid that removes OH-
- NH3 is the base that removes H+
We can show how H+ and OH- is removed via neutralisation reactions:
Since H+ and OH- is removed, therefore pH is maintained.
For the detailed step-by-step discussion on how an acidic and alkaline buffer work, check out this video!
Also learn how to calculate the pH of buffer solutions.
Topic: Ionic Equilibria, Physical Chemistry, A Level Chemistry, Singapore
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