1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of the acid and the ratio of the concentrations of the conjugate base (A⁻) and weak acid (HA). It's particularly useful for buffer solutions.

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
• \( [base] \) — Concentration of the conjugate base (mol/L)
• \( [acid] \) — Concentration of the weak acid (mol/L)

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

3. Importance of Buffer Calculations

Details: Buffer solutions resist changes in pH when small amounts of acid or base are added. They're essential in biological systems, chemical processes, and laboratory work.

4. Using the Calculator

Tips: Enter the pKa value of the acid, the concentration of the conjugate base, and the concentration of the acid. All concentrations must be in mol/L and greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for this equation?
A: The equation works best when the ratio [base]/[acid] is between 0.1 and 10 (pH within ±1 of pKa).

Q2: Can I use molarity or normality?
A: For this equation, always use molarity (mol/L) for both base and acid concentrations.

Q3: What if my base concentration is zero?
A: The equation becomes undefined when [base] = 0. In practice, buffers always contain some of both forms.

Q4: Does temperature affect the calculation?
A: Yes, pKa values are temperature-dependent, but this calculator assumes standard conditions (25°C).

Q5: Can I calculate concentrations from pH?
A: Yes, the equation can be rearranged to solve for the ratio [base]/[acid] if you know pH and pKa.