Henderson-Hasselbalch Calculator
Calculate buffer pH using pH = pKa + log([A-]/[HA]).
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Enter the pKa of the weak acid, the concentration of the conjugate base [A-], and the concentration of the weak acid [HA]. The calculator applies pH = pKa + log([A-]/[HA]) to give the buffer pH.
About the Henderson-Hasselbalch Calculator
The Henderson-Hasselbalch equation is a simplified expression derived from the acid dissociation equilibrium. It provides a quick way to estimate the pH of a buffer solution or to determine the ratio of acid to conjugate base needed to achieve a target pH. It is one of the most used equations in biochemistry and analytical chemistry.
Frequently Asked Questions
What is the Henderson-Hasselbalch equation?
The Henderson-Hasselbalch equation is pH = pKa + log([A-]/[HA]), where pKa is the acid dissociation constant, [A-] is the conjugate base concentration, and [HA] is the weak acid concentration. It relates pH to the ratio of conjugate base to weak acid in a buffer.
When is the Henderson-Hasselbalch equation most accurate?
The equation works best when the ratio [A-]/[HA] is between 0.1 and 10, meaning the buffer pH is within about 1 unit of pKa. Outside this range, the buffer capacity is too low for practical use.
What is pKa of acetic acid?
The pKa of acetic acid (CH3COOH) is 4.76 at 25 degrees Celsius. This means an acetate buffer works best in the pH range of roughly 3.76 to 5.76.