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Henderson-Hasselbalch Equation:
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The Henderson-Hasselbalch equation is used to estimate the pH of buffer solutions. For acetic acid/sodium acetate buffer systems, it relates pH to the concentrations of the weak acid and its conjugate base using the acid dissociation constant (pKa = 4.76 for acetic acid).
The calculator uses the Henderson-Hasselbalch equation:
Where:
Explanation: The equation calculates the pH based on the ratio of conjugate base to weak acid concentrations in the buffer solution.
Details: Accurate pH calculation is crucial for preparing buffer solutions with specific pH values, which are essential in biochemical experiments, pharmaceutical formulations, and various industrial processes.
Tips: Enter both acetate and acetic acid concentrations in mol/L. Both values must be positive numbers greater than zero for accurate calculation.
Q1: Why is the pKa value 4.76 for acetic acid?
A: 4.76 is the negative logarithm of the acid dissociation constant (Ka) for acetic acid at 25°C, which is approximately 1.76 × 10⁻⁵.
Q2: What is the effective buffer range for acetic acid/acetate buffer?
A: The effective buffer range is typically pKa ± 1, so pH 3.76 to 5.76 for acetic acid/acetate systems.
Q3: Can this equation be used for other buffer systems?
A: Yes, but with the appropriate pKa value for the specific weak acid/conjugate base pair.
Q4: What are the limitations of the Henderson-Hasselbalch equation?
A: It assumes ideal behavior, neglects activity coefficients, and may be less accurate at very low or very high concentrations or when the ratio is extreme.
Q5: How does temperature affect the calculation?
A: The pKa value changes with temperature, so for precise work, the pKa should be adjusted for the specific temperature of the solution.