PH PH In chemistry, pH () is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the molar concentration, measured in units of moles per liter, of hydrogen ions. More precisely it is the negative of the base 10 logarithm of the activity of the hydrogen ion. At 25 °C, solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. The neutral value of the pH depends on the temperature, being lower than 7 if the
Acid dissociation constant the added complication that the neutral molecule is subject to an internal acid–base equilibrium in which the basic amino group attracts and binds the proton from the acidic carboxyl group, forming a zwitterion. At pH less than about 5 both the carboxylate group and the amino group are protonated. As pH increases the acid dissociates according to At high pH a second dissociation may take place. Thus the zwitterion, , is amphoteric because it may either be protonated or deprotonated. The equilibrium constant "K" for a base is usually defined as the "association" constant for protonation of the base, B,