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Henderson-Hasselbalch Equation:
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The Henderson-Hasselbalch equation relates pH, pKa (acid dissociation constant), and the ratio of concentrations of a weak acid and its conjugate base in solution. It's widely used in chemistry and biochemistry to calculate pH or pKa in buffer systems.
The calculator uses the Henderson-Hasselbalch equation:
Where:
Explanation: The equation shows how the pH of a solution relates to the pKa of an acid and the ratio of its deprotonated (base) and protonated (acid) forms.
Details: Knowing pKa is essential for understanding acid-base chemistry, predicting protonation states, designing buffers, and drug formulation. It helps predict how molecules will behave at different pH levels.
Tips: Enter pH value, base concentration and acid concentration in molarity (M). All values must be valid (concentrations > 0).
Q1: What is the relationship between pKa and pH?
A: When pH equals pKa, the acid and its conjugate base are present in equal concentrations. The solution has maximum buffering capacity at this point.
Q2: What are typical pKa values?
A: For most organic acids, pKa ranges from 1-10. Strong acids have pKa < 0, while strong bases have conjugate acids with pKa > 14.
Q3: When is the Henderson-Hasselbalch equation not valid?
A: The equation assumes dilute solutions and doesn't account for activity coefficients. It's less accurate for very strong acids/bases or extreme pH values.
Q4: How does temperature affect pKa?
A: pKa values are temperature-dependent. Most reported values are for 25°C. Temperature changes can shift pKa by 0.01-0.1 units per °C.
Q5: Can this be used for polyprotic acids?
A: The equation applies to each dissociation step separately. For polyprotic acids, each proton has its own pKa value.