The concept of pKw It is used in the field of chemistry . The notion refers to a measure that is calculated by negative logarithm (-log ) of the water dissociation or ionization constant .
It is important to keep in mind that the pKw , he pH , he pKa , he pKb and other scales and constants refer to the alkalinity or acidity of a solution and the strength of the bases and acids. The appearance of a letter p at the beginning it always reveals that it is a negative logarithm: in this case, pKw is the -kw log .
Now what is Kw ? This is how the ionization or dissociation constant of Water , also called ionic water product .
Water can dissociate in its ions, although such dissociation is weak. The ionic product tends to remain constant, and the Kw It is the dissociation constant.
It can be said that the Kw is the equilibrium constant linked to the molarity of water in an aqueous solution. It should be noted that molarity or molar concentration indicates, in a solution, what is the concentration of a solute: it is a volume that depends on the temperature .
Therefore, although molarity is practically constant in aqueous solutions, pKw changes with temperature . If the temperature increases, the pKw is reduced; conversely, when the temperature drops, the pKw increases
Due to this rule, the usual thing is that the autoionization of the water grows next to the temperature. On the other hand, we must bear in mind that the Pressure it also affects - although slightly - in the pKw .