1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation is used to estimate the pH of a buffer solution from the pKa of the acid and the concentrations of the conjugate base [A⁻] and acid [HA]. It provides a simple way to calculate pH in acid-base chemistry.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — pH value (dimensionless)
• \( pKa \) — Acid dissociation constant (dimensionless)
• \( [A^-] \) — Concentration of conjugate base (mol/L)
• \( [HA] \) — Concentration of weak acid (mol/L)

Explanation: The equation relates pH, pKa, and the ratio of conjugate base to acid concentration in a buffer system.

3. Importance of pH Calculation

Details: Accurate pH calculation is crucial for understanding acid-base equilibria, designing buffer solutions, and predicting chemical behavior in biological and chemical systems.

4. Using the Calculator

Tips: Enter pKa value, [A⁻] and [HA] concentrations in mol/L. All concentration values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: When is the Henderson-Hasselbalch equation valid?
A: The equation is most accurate when the concentrations of [A⁻] and [HA] are similar and neither is too dilute.

Q2: What are typical pKa values?
A: pKa values range from -10 to 50, with common weak acids having pKa values between 2-12.

Q3: Can this equation be used for strong acids?
A: No, the Henderson-Hasselbalch equation is specifically designed for weak acid buffer systems.

Q4: What are the limitations of this equation?
A: The equation assumes ideal behavior and may be less accurate at extreme concentrations or when ionic strength effects are significant.

Q5: How does temperature affect the calculation?
A: pKa values are temperature-dependent, so calculations should use pKa values measured at the appropriate temperature.