Calculate Ph Of Buffer

Henderson-Hasselbalch Equation:

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

pH:

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1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation is used to estimate the pH of a buffer solution. It relates the pH, pKa (acid dissociation constant), and the ratio of the concentrations of the conjugate base [A⁻] to the weak acid [HA] in the buffer system.

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 shows that the pH of a buffer solution depends on the pKa of the weak acid and the ratio of the concentrations of its conjugate base to the acid form.

3. Importance of Buffer pH Calculation

Details: Accurate pH calculation is crucial for preparing buffer solutions in biochemical experiments, pharmaceutical formulations, and various industrial processes where maintaining a stable pH is essential.

4. Using the Calculator

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

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, which corresponds to pH values within ±1 unit of the pKa.

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 and is not applicable to strong acids or bases.

Q3: What are typical pKa values for common buffer systems?
A: Common biological buffers include acetic acid (pKa = 4.76), phosphoric acid (pKa = 7.2), and Tris (pKa = 8.06).

Q4: How does temperature affect the calculation?
A: pKa values are temperature-dependent. For precise work, use pKa values measured at the temperature of interest.

Q5: What are the limitations of this equation?
A: The equation assumes ideal behavior and may not account for ionic strength effects or activity coefficients, which can be significant at high concentrations.