Ph Of Buffer Calculator

Henderson-Hasselbalch Equation:

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

Calculated 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. 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:

\( pH \) — The calculated pH of the buffer solution
\( pKa \) — The acid dissociation constant of the weak acid
\( [A⁻] \) — Concentration of the conjugate base (mol/L)
\( [HA] \) — Concentration of the 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 conjugate base to weak acid concentrations.

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 the pKa value of the weak acid, and the concentrations of both the conjugate base [A⁻] and weak acid [HA] in mol/L. All values must be valid (concentrations > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the valid range for this equation?
A: The equation works best when the ratio [A⁻]/[HA] is between 0.1 and 10, and when the concentrations are within one order of magnitude of each other.

Q2: When is the buffer most effective?
A: A buffer is most effective when pH = pKa, meaning [A⁻] = [HA], giving the maximum buffering capacity.

Q3: What are common buffer systems?
A: Common buffer systems include acetate (pKa = 4.76), phosphate (pKa = 7.21), and Tris (pKa = 8.07).

Q4: Are there limitations to this equation?
A: The equation assumes ideal behavior and may not be accurate for very concentrated solutions or when ionic strength effects are significant.

Q5: Can this equation be used for polyprotic acids?
A: For polyprotic acids, each dissociation has its own pKa value, and the equation must be applied to the relevant acid-base pair.