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[c] [2] For example, a hypothetical weak acid having K a = 10 −5, the value of log K a is the exponent (−5), giving pK a = 5. For acetic acid, K a = 1.8 x 10 −5, so pK a is 4.7. A higher K a corresponds to a stronger acid (an acid that is more dissociated at equilibrium).
In computational biology, protein pK a calculations are used to estimate the pK a values of amino acids as they exist within proteins.These calculations complement the pK a values reported for amino acids in their free state, and are used frequently within the fields of molecular modeling, structural bioinformatics, and computational biology.
For example, the acid may be acetic acid and the salt may be sodium acetate. The Henderson–Hasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant, K a of the acid, and the concentrations of the species in solution. [6]
Chemicals with high partition coefficients, for example, tend to accumulate in the fatty tissue of organisms (bioaccumulation). Under the Stockholm Convention, chemicals with a log K ow greater than 5 are considered to bioaccumulate. [7] Furthermore, the parameter plays an important role in drug research (Rule of Five) and toxicology.
An example of this case would be the splitting of hydrochloric acid HCl in water. Since HCl is a strong acid (it splits up to a large extent), its conjugate base (Cl −) will be weak. Therefore, in this system, most H + will be hydronium ions H 3 O + instead of attached to Cl − anions and the conjugate bases will be weaker than water molecules.
Acid strength is the tendency of an acid, symbolised by the chemical formula, to dissociate into a proton, +, and an anion, .The dissociation or ionization of a strong acid in solution is effectively complete, except in its most concentrated solutions.
For example, the blood/gas partition coefficient of a general anesthetic measures how easily the anesthetic passes from gas to blood. [5] Partition coefficients can also be defined when one of the phases is solid , for instance, when one phase is a molten metal and the second is a solid metal, [ 6 ] or when both phases are solids. [ 7 ]
Since Tris' pKa is more strongly temperature dependent, its use is not recommended in biochemical applications requiring consistent pH over a range of temperatures. Moreover, the temperature dependance of the pKa (and in turn buffer solution pH) makes pH adjustment difficult. [8] (E.g., the 'room temperature' pH adjustment would not translate ...