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 the concentrations of the conjugate base (A⁻) and weak acid (HA) in a buffer system. It's particularly useful in acid-base chemistry and biochemistry.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — The calculated pH of the solution
• \( pKa \) — The acid dissociation constant
• \( [\text{base}] \) — Concentration of conjugate base (A⁻)
• \( [\text{acid}] \) — Concentration of weak acid (HA)

Explanation: The equation shows that pH equals pKa when the concentrations of acid and base are equal (ratio = 1, log(1) = 0).

3. Importance of pH Calculation

Details: Accurate pH calculation is crucial for buffer preparation, pharmaceutical formulations, biological systems, and chemical reactions where pH control is essential.

4. Using the Calculator

Tips: Enter pKa value, base concentration, and acid concentration in mol/L. All values must be positive numbers (acid concentration cannot be zero).

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for pKa values?
A: Most pKa values range between 0-14, though some very strong acids can have negative pKa values.

Q2: What units should I use for concentrations?
A: The calculator uses molarity (mol/L), but any consistent concentration units can be used since the equation uses a ratio.

Q3: When is the Henderson-Hasselbalch equation most accurate?
A: It works best when the concentrations of acid and conjugate base are between 0.1-10 times the pKa value.

Q4: Can I use this for strong acids or bases?
A: No, the equation is only valid for weak acid/conjugate base buffer systems.

Q5: How does temperature affect the calculation?
A: Temperature affects pKa values, so use the pKa value appropriate for your experimental temperature.