Home
Back
Henderson-Hasselbalch Equation:
| From: | To: |
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 and weak acid in the buffer system.
The calculator uses the Henderson-Hasselbalch equation:
Where:
Explanation: The equation demonstrates how the pH of a buffer solution depends on the pKa of the acid and the ratio of base to acid concentrations.
Details: Accurate pH calculation is crucial for understanding buffer capacity, predicting chemical behavior in biological systems, and designing experiments in biochemistry and molecular biology.
Tips: Enter pKa value, base concentration in molarity (M), and acid concentration in molarity (M). All values must be valid (base > 0, acid > 0).
Q1: What is the typical pKa value for histidine?
A: The imidazole group of histidine has a pKa of approximately 6.0, making it an effective buffer in physiological pH ranges.
Q2: When is the Henderson-Hasselbalch equation most accurate?
A: The equation is most accurate when the concentrations of acid and base are significantly larger than the concentration of H⁺ and OH⁻ ions.
Q3: What are the limitations of this equation?
A: The equation assumes ideal behavior and may not be accurate for very concentrated solutions or when ionic strength effects are significant.
Q4: Can this equation be used for polyprotic acids?
A: For polyprotic acids, each dissociation step has its own pKa value and the equation must be applied separately for each buffering region.
Q5: Why is histidine commonly used as a buffer?
A: Histidine is commonly used because its pKa (around 6.0) falls within the physiological pH range, and it is biologically compatible.