1. What is the Buffer pH Equation?

The Henderson-Hasselbalch equation calculates the pH of a buffer solution from the pKa of the acid and the ratio of conjugate base to acid concentrations. It's essential for understanding and preparing buffer solutions in chemistry and biochemistry.

2. How Does the Calculator Work?

The calculator uses the buffer pH equation:

Where:

• \( pH \) — pH value (dimensionless)
• \( pKa \) — Acid dissociation constant (dimensionless)
• \( C_b \) — Base concentration (mol/L)
• \( V_b \) — Base volume (L)
• \( C_a \) — Acid concentration (mol/L)
• \( V_a \) — Acid volume (L)

Explanation: The equation relates the pH of a buffer to the pKa of the weak acid and the ratio of the concentrations of its conjugate base and acid forms.

3. Importance of Buffer pH Calculation

Details: Accurate pH calculation is crucial for preparing buffer solutions in laboratory experiments, pharmaceutical formulations, and biological studies where maintaining stable pH is essential.

4. Using the Calculator

Tips: Enter pKa value, base concentration and volume, acid concentration and volume. All values must be positive numbers with appropriate units.

5. Frequently Asked Questions (FAQ)

Q1: What is the range of validity for this equation?
A: The equation works best when the concentrations of acid and conjugate base are within a factor of 10 of each other.

Q2: Why use volumes in the calculation?
A: When mixing solutions, the ratio of moles (concentration × volume) determines the buffer ratio, not just concentrations.

Q3: What are typical pKa values?
A: Common buffer pKa values range from 1-12, with biological buffers typically around 6-8 (e.g., phosphate pKa = 7.2).

Q4: When is this equation not accurate?
A: For very dilute solutions, high ionic strength, or when the acid concentration is extremely low compared to the base.

Q5: Can this be used for polyprotic acids?
A: For polyprotic acids, the equation applies to each dissociation step separately, considering the appropriate pKa and concentrations.