buffer solution

What is a buffer solution?

A buffer solution is an aqueous solution that resists significant changes in pH upon the addition of small amounts of an acid or a base.

What are the two main types of buffer solutions?

1. Acidic Buffer: Consists of a weak acid and its conjugate base (e.g., CH3COOH and CH3COO^-
2. Basic Buffer: Consists of a weak base and its conjugate acid (e.g., NH3 and NH4^+$)

In both cases, the conjugate base or acid is typically provided by a salt (e.g., CH3COONa or NH4Cl).

How does an acidic buffer resist pH changes when a strong acid is added?

When a strong acid (H3O^+ or H^+) is added to an acidic buffer, the conjugate base component of the buffer (e.g., A^-, from CH3COO^-) reacts with the added H^+ to form the weak acid (e.g., HA or CH_3COOH).

A^- + H^+ \rightleftharpoons HA

This consumes the added H^+, preventing a large drop in pH.

How does an acidic buffer resist pH changes when a strong base is added?

When a strong base (OH^-) is added to an acidic buffer, the weak acid component of the buffer (e.g., HA or CH3COOH) reacts with the added OH^- to form water and the conjugate base (e.g., A^- or CH3COO^-).

HA + OH^- \rightleftharpoons A^- + H_2O

This consumes the added OH^-, preventing a large increase in pH.