Calculate Ph of 0.010 M Sodium Acetate

Introduction

The pH of a solution is a measure of its acidity or alkalinity. Sodium acetate (CH₃COONa) is a weak base that forms a buffer solution when combined with acetic acid (CH₃COOH). The pH of such a buffer solution can be calculated using the Henderson-Hasselbalch equation.

In this guide, we'll calculate the pH of a 0.010 M sodium acetate solution, which is a common concentration used in laboratory settings. We'll also discuss the principles of buffer solutions and provide practical examples.

How to Calculate pH

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:

Where:

• pH is the acidity of the solution
• pKa is the acid dissociation constant of the acid
• [A⁻] is the concentration of the conjugate base (sodium acetate)
• [HA] is the concentration of the acid (acetic acid)

For a sodium acetate solution, the pKa of acetic acid is approximately 4.76. If the solution is 0.010 M sodium acetate, the concentration of acetic acid is also 0.010 M (assuming equal concentrations of the conjugate base and acid).

Buffer Solutions

Buffer solutions resist changes in pH when small amounts of acid or base are added. This is because they contain a weak acid and its conjugate base. In the case of sodium acetate, it acts as the conjugate base, while acetic acid is the weak acid.

Buffer solutions are widely used in laboratory settings to maintain a stable pH for biochemical reactions. Understanding how to calculate the pH of a buffer solution is crucial for many scientific applications.

Example Calculation

Let's calculate the pH of a 0.010 M sodium acetate solution:

1. Identify the pKa of acetic acid: 4.76
2. Determine the concentration of sodium acetate ([A⁻]): 0.010 M
3. Determine the concentration of acetic acid ([HA]): 0.010 M
4. Plug the values into the Henderson-Hasselbalch equation:
   pH = 4.76 + log(0.010 / 0.010) = 4.76 + log(1) = 4.76 + 0 = 4.76

The pH of a 0.010 M sodium acetate solution is 4.76.