What Is the Henderson-Hasselbalch Buffer pH Calculator?
The Henderson-Hasselbalch equation relates the pH of an aqueous solution to the dissociation constant pKa of a weak acid and the ratio of conjugate species.
Buffer solutions resist changes in hydronium ion concentration upon addition of small amounts of strong acid or base.
How Does the Henderson-Hasselbalch Buffer pH Calculator Work?
The ratio of conjugate base [A⁻] to weak acid [HA] is determined.
The base-10 logarithm log₁₀([A⁻]/[HA]) is calculated.
Adding this term to pKa yields the predicted equilibrium pH.
Henderson-Hasselbalch Buffer pH Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Buffer pH equals acid dissociation constant pKa plus the base-10 logarithm of conjugate base to weak acid concentration ratio.
How to Use the Henderson-Hasselbalch Buffer pH Calculator
- Enter the pKa of your buffering agent at the working temperature.
- Enter the molar concentrations of conjugate base and weak acid.
- Examine the resulting pH and buffer capacity quality indicator.
Step-by-Step Example Calculation
Equal acetate buffer (0.1 M / 0.1 M)
Input Values:
Understanding Your Result
When base and acid are in equal concentration (1:1), solution pH equals pKa.
Effective buffering capacity is maintained when pH remains within pKa ± 1.0 unit.
Factors That Affect the Result
- Temperature: pKa values of amine buffers like Tris shift noticeably with temperature.
- Ionic Strength: High salt concentrations alter activity coefficients away from ideal molarity.
When Should You Use This Calculator?
- Formulating biological buffers for cell culture, enzyme assays, and chromatography.
- General and analytical chemistry titration calculations.
Assumptions & Limitations
- Assumes dilute solutions where concentration approximates chemical activity.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Evaluates classic Henderson-Hasselbalch thermodynamic equilibrium.