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Henderson-Hasselbalch Equation:
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The Henderson-Hasselbalch equation is used to estimate the pH of a buffer solution during titration. It relates pH, pKa (acid dissociation constant), and the ratio of the concentration of the conjugate base to the concentration of the weak acid.
The calculator uses the Henderson-Hasselbalch equation:
Where:
Explanation: The equation is valid in the buffer region of a titration curve where the ratio of added to remaining species determines the pH.
Details: Accurate pH calculation during titration is crucial for determining equivalence points, understanding buffer capacity, and predicting the behavior of acid-base systems in chemical and biological processes.
Tips: Enter pKa value, amount of titrant added (mol), and amount of acid/base remaining (mol). All values must be valid positive numbers.
Q1: When is the Henderson-Hasselbalch equation valid?
A: The equation is valid in the buffer region of a titration curve, typically when the ratio of [A-]/[HA] is between 0.1 and 10.
Q2: What are typical pKa values for common acids?
A: Acetic acid: 4.76, Phosphoric acid: 2.15, 7.20, 12.35, Carbonic acid: 6.35, 10.33.
Q3: Can this equation be used for polyprotic acids?
A: For polyprotic acids, the equation can be applied to each dissociation step separately when the pKa values are sufficiently separated.
Q4: What are the limitations of the Henderson-Hasselbalch equation?
A: The equation assumes ideal behavior, constant temperature, and may not be accurate for very dilute solutions or when the ratio is far from 1.
Q5: How does temperature affect the calculation?
A: Both pKa and pH are temperature-dependent. For precise calculations, values should be corrected for the specific temperature of the system.