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The pH range is commonly given as zero to 14, but a pH value can be less than 0 for very concentrated strong acids or greater than 14 for very concentrated strong bases. [2] The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. [3]
Solutions with a pH value below 7.0 are considered acidic and solutions with pH value above 7.0 are basic. Since most naturally occurring organic compounds are weak electrolytes , such as carboxylic acids and amines , pH indicators find many applications in biology and analytical chemistry .
The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). [1] However, pI is also used. [2] For brevity, this article uses pI.
The point of zero charge is the pH value for which the net surface charge of adsorbent is equal to zero. This concept has been introduced by an increase of interest in the pH of the solution during adsorption experiments. [1]
In particular, the pH of a solution can be predicted when the analytical concentration and pK a values of all acids and bases are known; conversely, it is possible to calculate the equilibrium concentration of the acids and bases in solution when the pH is known. These calculations find application in many different areas of chemistry, biology ...
In chemistry and biochemistry, the Henderson–Hasselbalch equation = + ([] []) relates the pH of a chemical solution of a weak acid to the numerical value of the acid dissociation constant, K a, of acid and the ratio of the concentrations, [] [] of the acid and its conjugate base in an equilibrium.
Given its greater H + concentration, the formula yields a lower pH value for the weak base. However, pH of bases is usually calculated in terms of the OH − concentration. This is done because the H + concentration is not a part of the reaction, whereas the OH − concentration is. The pOH is defined as:
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately pK a ± 1. When choosing a buffer for use at a specific pH, it should have a pK a value as close as possible to that pH. [2]