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 base and acid forms of a buffer system. It's widely used in chemistry and biochemistry to calculate buffer pH.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — The calculated pH of the buffer solution
• \( pKa \) — The acid dissociation constant of the weak acid
• \( [base] \) — Concentration of the conjugate base (mol/L)
• \( [acid] \) — Concentration of the 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: Buffer solutions resist changes in pH when small amounts of acid or base are added. Calculating buffer pH is essential in biological systems, chemical experiments, and pharmaceutical preparations.

4. Using the Calculator

Tips: Enter pKa value, base concentration, and acid concentration in mol/L. All concentrations must be positive values.

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for this equation?
A: The equation is valid when the concentrations of acid and base are within about 10-fold of each other (0.1 < [base]/[acid] < 10).

Q2: What are typical pKa values?
A: Common buffer pKa values: acetic acid (4.76), phosphate (7.21), Tris (8.07), bicarbonate (10.3).

Q3: When is this equation not accurate?
A: The equation assumes ideal behavior and may be less accurate at very high or low ionic strengths or with polyprotic acids.

Q4: How does temperature affect the calculation?
A: pKa values are temperature-dependent, so use the pKa appropriate for your experimental temperature.

Q5: Can I use molarity or molality?
A: The equation uses concentrations. For dilute solutions, molarity (mol/L) is appropriate.