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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