1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation relates the pH of a solution to the pKa (acid dissociation constant) and the ratio of concentrations of the conjugate base and weak acid in a buffer system. It's widely used in chemistry and biochemistry to predict and control pH in buffer solutions.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — Negative logarithm of hydrogen ion concentration
• \( pKa \) — Negative logarithm of the acid dissociation constant
• \( [base] \) — Concentration of conjugate base (mol/L)
• \( [acid] \) — Concentration of weak acid (mol/L)

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

3. Importance of Buffer pH Calculation

Details: Accurate pH calculation is crucial for preparing buffer solutions in biological systems, chemical experiments, and pharmaceutical formulations where maintaining stable pH is essential.

4. Using the Calculator

Tips: Enter pKa value, base and acid concentrations in mol/L. All values must be positive numbers. The base/acid ratio should be within the buffer's effective range (typically 0.1 to 10).

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for this equation?
A: The equation works best when [base]/[acid] ratio is between 0.1 and 10 (buffer range). Outside this range, other species may contribute significantly to pH.

Q2: What are common buffer systems?
A: Common systems include acetic acid/acetate (pKa 4.76), phosphate (pKa 7.2), and Tris (pKa 8.1).

Q3: Does temperature affect the calculation?
A: Yes, pKa values are temperature-dependent. Use the pKa value appropriate for your experimental temperature.

Q4: What if my acid is polyprotic?
A: For polyprotic acids, use the pKa closest to your desired pH and the corresponding conjugate base.

Q5: How precise is this calculation?
A: It's a good approximation for dilute solutions (<0.1M). For more precise calculations, activity coefficients should be considered.