Formula To Calculate PH Of A Buffer Solution

Henderson-Hasselbalch Equation:

\[ pH = pKa + \log_{10}\left(\frac{[A^-]}{[HA]}\right) \]

Calculated 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⁻] and weak acid [HA] in the solution.

2. How Does The Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

\[ pH = pKa + \log_{10}\left(\frac{[A^-]}{[HA]}\right) \]

Where:

\( pKa \) — Acid dissociation constant (unitless)
\( [A^-] \) — Concentration of conjugate base (mol/L)
\( [HA] \) — Concentration of weak acid (mol/L)

Explanation: The equation demonstrates that the pH of a buffer solution depends on the pKa of the weak acid and the log of the ratio of conjugate base to acid concentrations.

3. Importance Of pH Calculation In Buffer Solutions

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

4. Using The Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is a buffer solution?
A: A buffer solution resists changes in pH when small amounts of acid or base are added, maintaining a relatively constant pH.

Q2: When is the Henderson-Hasselbalch equation most accurate?
A: The equation is most accurate when the concentrations of [A⁻] and [HA] are within an order of magnitude of each other and when the pH is close to the pKa value.

Q3: Can this equation be used for strong acids or bases?
A: No, the Henderson-Hasselbalch equation is specifically designed for weak acid-base pairs and is not applicable to strong acids or bases.

Q4: What are common buffer systems?
A: Common buffer systems include acetic acid/acetate (pKa=4.76), phosphate (pKa=7.2), and Tris (pKa=8.06).

Q5: What are the limitations of this equation?
A: The equation assumes ideal behavior and may not be accurate at very high or very low concentrations, or when the ionic strength of the solution is high.