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Henderson-Hasselbalch Equation:
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The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of the acid and the ratio of the concentrations of the conjugate base (A⁻) and acid (HA). It's particularly useful for buffer solutions.
The calculator uses the Henderson-Hasselbalch equation:
Where:
Explanation: The equation shows that the pH of a buffer depends on the pKa of the weak acid and the ratio of base to acid concentrations.
Details: Accurate pH calculation is crucial for preparing buffer solutions in biological and chemical research, pharmaceutical formulations, and industrial processes where maintaining stable pH is essential.
Tips: Enter pKa value (typically between 0-14), base concentration (mol/L), and acid concentration (mol/L). All values must be positive numbers.
Q1: What is a buffer solution?
A: A buffer is a solution that resists changes in pH when small amounts of acid or base are added, typically composed of a weak acid and its conjugate base.
Q2: What is the effective range of a buffer?
A: A buffer is most effective when the pH is within ±1 unit of the pKa (buffer capacity is highest when [base] = [acid]).
Q3: When is the Henderson-Hasselbalch equation not valid?
A: The equation may not be accurate for very dilute solutions (<1 mM) or for very strong acids/bases (pH < 2 or > 12).
Q4: Can I use molar ratios instead of concentrations?
A: Yes, since the equation uses a ratio, you can use either concentrations or mole amounts (as long as both base and acid are in the same units).
Q5: How does temperature affect pH calculations?
A: pKa values are temperature-dependent, so for precise work, use the pKa value at your experimental temperature.