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For an aqueous solution of a weak acid, the dissociation constant is called the acid ionization constant (Ka). Similarly, the equilibrium constant for the reaction of a weak base with water is the base ionization constant (Kb).
pKa is the negative base 10 logarithm of the acid dissociation constant, Ka. In a way, both pKa and Ka give you the same information, but the Ka value is a small decimal number that is easy to work with, while Ka has exponents and uses scientific notation.
The pH scale is the most familiar measure of acidity and basicity, but pKa, pKb, Ka, and Kb are better for predicting acid and base strength and their reactions. Here are definitions of each term, simple formulas used to calculate them, and an explanation of how they differ from one another.
The acidity constant Ka is the equilibrium constant for dissociation of an acid into its conjugate base and H+. Pka is the negative logarithm of Ka.
The pH scale measures the hydrogen ion concentration in a solution, indicating whether it is acidic, neutral, or basic. The terms pKa and pKb represent the negative logarithms of the acid and base dissociation constants, Ka and Kb, respectively. They help determine the strength of acids and bases.
Acid Ionization Constant (Ka) Aside from the qualitative comparison of the acid strength, we need a quantitative definition for the acid strength. For weak acids, the dissociation is a reversible reaction described by an equilibrium constant (Keq) which, for the ionization of acids is denoted as Ka.
pKa - The pKa value is the negative base -10 logarithm of the acid dissociation constant (Ka) of a solution. The quantitative behavior of acids and bases in solution can be understood only if their pKa values are known.
The reason pKa is used is because it describes acid dissociation using small decimal numbers. The same type of information may be obtained from Ka values, but they're typically extremely small numbers given in scientific notation that are hard for most people to understand.
The acid dissociation constant (Ka) is used to differentiate between strong and weak acids. The acid dissociates more as the Ka increases. Strong acids must therefore dissociate more in water. A weak acid, on the other hand, is less likely to ionise and release a hydrogen ion, leading to a less acidic solution.
Because the inductive effect depends on electronegativity, fluorine substituents have a more pronounced pKa-lowered effect than chlorine substituents. In addition, the inductive takes place through covalent bonds, and its influence decreases markedly with distance – thus a chlorine two carbons away from a carboxylic acid group has a decreased ...