Henderson-Hasselbalch Calculator

Formula

To calculate the pH using the Henderson-Hasselbalch equation:

\[ pH = K_a + \log \left( \frac{[A^-]}{[HA]} \right) \]

Where:

\(pH\) is the measure of the acidity of the solution
\(K_a\) is the acid dissociation constant
\([A^-]\) is the molar concentration of the base
\([HA]\) is the molar concentration of the acid

Henderson-Hasselbalch Equation Definition

The Henderson-Hasselbalch equation is a formula used to calculate the pH (acidity) of a buffer. The equation is denoted:

\[ pH = K_a + \log \left( \frac{[A^-]}{[HA]} \right) \]

A buffer is a mixture or solution that contains a weak acid and a conjugate base. The combination of these two components, while at equilibrium, helps to maintain a stable pH in the solution.

Example Calculation 1

Let's assume the following values:

Acid Dissociation Constant (\(K_a\)) = 4.75
Molar Concentration of Base (\([A^-]\)) = 0.1 M
Molar Concentration of Acid (\([HA]\)) = 0.2 M

Using the formula:

\[ pH = 4.75 + \log \left( \frac{0.1}{0.2} \right) = 4.75 + \log (0.5) \approx 4.75 + (-0.3010) = 4.06 \]

The pH of the solution is approximately 4.06.

Example Calculation 2

Let's assume the following values:

Acid Dissociation Constant (\(K_a\)) = 3.75
Molar Concentration of Base (\([A^-]\)) = 0.05 M
Molar Concentration of Acid (\([HA]\)) = 0.05 M

Using the formula:

\[ pH = 3.75 + \log \left( \frac{0.05}{0.05} \right) = 3.75 + \log (1) = 3.75 + 0 = 3.75 \]

The pH of the solution is approximately 3.75.