Henderson–Hasselbalch equation

Henderson–Hasselbalch equation

The Henderson–Hasselbalch equation is a mathematical formula that describes the relationship between the pH and pKa of a weak acid. It is named after the American chemists Lawrence Joseph Henderson and Karl Albert Hasselbalch, who independently developed the equation in the early 20th century.

Overview

The Henderson–Hasselbalch equation is given by:

pH = pKa + log ([A-]/[HA])

where:

• pH is the acid dissociation constant
• pKa is the negative logarithm (base 10) of the Ka
• [A-] is the concentration of the base (conjugate base)
• [HA] is the concentration of the acid

The equation is used in the study of acid-base homeostasis in the human body, particularly in medicine and biology. It is also used in the field of Pharmacology, especially in the development of new drugs and in understanding drug interactions.

Applications in Medicine

In medicine, the Henderson–Hasselbalch equation is used to calculate the pH of blood and other bodily fluids. This is important in the diagnosis and treatment of many diseases, including Acidosis and Alkalosis, which are caused by an imbalance in the body's pH levels.

Applications in Pharmacology

In pharmacology, the Henderson–Hasselbalch equation is used to predict the ionization state of drugs. This is important in understanding how drugs are absorbed, distributed, metabolized, and excreted in the body. The equation can also be used to determine the optimal pH for drug formulation and storage.

See also

• Acid-base reaction
• Buffer solution
• Chemical equilibrium
• Chemical kinetics