1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation relates pH, pKa, and the ratio of concentrations of a weak acid and its conjugate base in solution. It's particularly useful for calculating the pH of buffer solutions.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pKa \) — Acid dissociation constant (negative log of Ka)
• \( [base] \) — Concentration of conjugate base (mol/L)
• \( [acid] \) — Concentration of 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 pH Calculation

Details: Accurate pH calculation is crucial for understanding chemical reactions, biological systems, and preparing buffer solutions in laboratory and industrial settings.

4. Using the Calculator

Tips: Enter pKa value, base concentration, and acid concentration in mol/L. All values must be valid (concentrations > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for this equation?
A: The equation works best when pH is within ±1 unit of the pKa, where the buffer is most effective.

Q2: What are typical pKa values?
A: pKa values vary widely: acetic acid (4.76), phosphoric acid (2.15, 7.20, 12.35), ammonium ion (9.25).

Q3: Can I use molarity or activity?
A: For dilute solutions (<0.1M), molarity is sufficient. For concentrated solutions, activity coefficients should be considered.

Q4: What if [base] = [acid]?
A: When [base] = [acid], pH = pKa since log(1) = 0.

Q5: Does temperature affect the calculation?
A: Yes, pKa values are temperature-dependent, though this calculator uses the pKa value you provide.