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Stepwise dissociation constants are each defined for the loss of a single proton. The constant for dissociation of the first proton may be denoted as K a1 and the constants for dissociation of successive protons as K a2, etc. Phosphoric acid, H 3 PO 4, is an example of a polyprotic acid as it can lose three protons.
3 (i.e. the first acid dissociation constant for carbonic acid), K 2 is the equilibrium constant for the reaction HCO − 3 ⇌ H + + CO 2− 3 (i.e. the second acid dissociation constant for carbonic acid), and DIC is the (unchanging) total concentration of dissolved inorganic carbon in the system, i.e. [CO 2] + [HCO − 3] + [CO 2− 3].
Nevertheless, one can generally examine acid dissociation constants to qualitatively predict or rationalize rate or reactivity trends relating to variation of the leaving group. Consistent with this picture, strong bases such as OH −, OR 2 and NR − 2 tend to make poor leaving groups, due their inability to stabilize a negative charge.
In chemistry, biochemistry, and pharmacology, a dissociation constant (K D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.
K a is variously named a dissociation constant, [3] an acid ionization constant, [2]: 668 an acidity constant [1] or an ionization constant. [2]: 708 It serves as an indicator of the acid strength: stronger acids have a higher K a value (and a lower pK a value).
The strength of a weak acid is quantified by its acid dissociation constant, value. The strength of a weak organic acid may depend on substituent effects. The strength of an inorganic acid is dependent on the oxidation state for the atom to which the proton may be attached. Acid strength is solvent-dependent.
where log denotes a logarithm to base 10 or common logarithm, and K diss is a stepwise acid dissociation constant. For bases, the base association constant, pK b is used. For any given acid or base the two constants are related by pK a + pK b = pK w, so pK a can always be used in calculations.
The role of water in the association equilibrium is ignored as in all but the most concentrated solutions the activity of water is constant. K is defined here as an association constant, the reciprocal of an acid dissociation constant. Each activity term { } can be expressed as the product of a concentration [ ] and an activity coefficient γ ...