1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation relates pH, pKa, and the ratio of base to acid concentrations in a buffer solution. For Tris buffer (pKa ≈8.07 at 25°C), it provides a way to calculate the pH based on the concentrations of the basic and acidic forms.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( \text{pH} \) — Negative logarithm of hydrogen ion concentration
• \( \text{pKa} \) — Acid dissociation constant (8.07 for Tris at 25°C)
• \( [\text{base}] \) — Concentration of basic form (Tris)
• \( [\text{acid}] \) — Concentration of acidic form (Tris-H+)

Explanation: The equation shows that buffer pH depends on the pKa of the weak acid and the ratio of its conjugate base to acid concentrations.

3. Importance of pH Calculation

Details: Accurate pH calculation is crucial for preparing biological buffers, maintaining enzyme activity, and ensuring proper experimental conditions in biochemical research.

4. Using the Calculator

Tips: Enter pKa value (default is 8.07 for Tris), base and acid concentrations in mol/L. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical pKa for Tris buffer?
A: The pKa of Tris is approximately 8.07 at 25°C, but this varies slightly with temperature (decreases by ~0.03 units per °C increase).

Q2: What are common Tris buffer concentrations?
A: Tris buffers are commonly prepared in the range of 10-100 mM, with pH adjusted using HCl or NaOH.

Q3: How does temperature affect Tris buffer pH?
A: Tris buffer has a significant temperature coefficient (~-0.028 pH units per °C). The pH should be measured at the temperature of use.

Q4: What is the effective buffer range for Tris?
A: Tris is effective in the pH range of about 7.0-9.0 (pKa ±1), with optimal buffering capacity at pH = pKa.

Q5: Why use Tris buffer?
A: Tris is widely used in biochemistry because it's nontoxic, highly soluble, and effective in the physiological pH range.