Acid dissociation constant

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Acid Dissociation Constant

The Acid Dissociation Constant (pronounced as: a-sid dis-so-see-ay-shun kon-stant), often denoted by the symbol Ka, is a fundamental concept in chemistry that quantifies the strength of an acid in solution. It is the equilibrium constant for a chemical reaction known as a proton transfer reaction, or acid dissociation.

Etymology

The term "Acid Dissociation Constant" is derived from the process it describes. "Acid" refers to the substance that donates protons or hydrogen ions in a solution. "Dissociation" refers to the breaking down of the acid into its constituent ions. "Constant" refers to the equilibrium state of the reaction, indicating that the ratio of the concentrations of the products to the reactants remains constant.

Definition

The Acid Dissociation Constant, Ka, is defined by the following equation:

Ka = [A-][H3O+] / [HA]

where [HA] is the concentration of the acid, [A-] is the concentration of the base formed by the acid's dissociation, and [H3O+] is the concentration of the hydronium ion.

Related Terms

  • pKa: The negative logarithm of the Acid Dissociation Constant. It provides a measure of the strength of an acid in solution. A lower pKa value indicates a stronger acid.
  • Base Dissociation Constant (Kb): The equilibrium constant for the dissociation of a base into its constituent ions in a solution.
  • pH: A measure of the acidity or alkalinity of a solution. It is the negative logarithm of the concentration of hydronium ions in a solution.
  • Equilibrium Constant (K): A measure of the ratio of the concentrations of products to reactants at equilibrium in any chemical reaction.

See Also

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