Formula For Calculating Ph Of Buffer

Henderson-Hasselbalch Equation:

\[ pH = pKa + \log\left(\frac{[A⁻]}{[HA]}\right) \]

pH:

Unit Converter ▲

Unit Converter ▼

From:	To:

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 the pH of buffer systems in chemistry and biochemistry.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

\[ pH = pKa + \log\left(\frac{[A⁻]}{[HA]}\right) \]

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 the pH of a solution to the pKa and the ratio of the concentrations of the conjugate base and weak acid.

3. Importance of pH Calculation

Details: Accurate pH calculation is crucial for understanding buffer capacity, predicting chemical behavior, and maintaining stable pH conditions in biological and chemical systems.

4. Using the Calculator

Tips: Enter pKa value, concentrations of conjugate base [A⁻] and weak acid [HA] in mol/L. All concentration values must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for the Henderson-Hasselbalch equation?
A: The equation is most accurate when the ratio [A⁻]/[HA] is between 0.1 and 10, and when the concentrations are within the buffer's effective range.

Q2: Can this equation be used for strong acids or bases?
A: No, the Henderson-Hasselbalch equation is specifically designed for weak acid-base buffer systems.

Q3: What are typical pKa values for common buffers?
A: Common buffers have pKa values around physiological pH (7.4), such as phosphate (pKa 7.2) and Tris (pKa 8.1).

Q4: Are there limitations to this equation?
A: The equation assumes ideal behavior and may be less accurate at very high or low concentrations, or when ionic strength effects are significant.

Q5: How does temperature affect the calculation?
A: Temperature affects both pKa values and pH measurements, so calculations should use pKa values at the appropriate temperature.