Diprotic acids, defined

We derive the key equation for a diprotic acid, H2A, and extend it to a general acid, H A. The mean fraction of protons bound to H2A ranges from 0 to 2 and is defined as... 

Another constraint equation often used in equilibrium problems is the proton balance equation (PBE) (Pankow, 1991). It provides a means of keeping account of protons in the system. A PBE can be formulated by writing an MBE in which the concentration of each species in the EPM table is multiplied by the stoichiometric coefficient of H in the EPM table. For example, the PBE of a diprotic acid H2L where the components that define the species are H2L and H+ would be... 

Following the approach of Tanford (1961), it is useful to examine the ionization of a hypothetical diprotic acid (HA-BH). Thermodynamically, the acid-base properties of this acid are completely described by two acid dissociation constants ( fi and K2). However, at the molecular level, it is clearly more appropriate to define four dissociation constants as depicted in Equation (2) ... 

These equations may be compared with Equations 7.72 through 7.75 in Chapter 7 for a s. They are somewhat different in form because the equilibria were written as associations rather than dissociations. If dissociation constants were used in place of formation constants, the equations would be identical to the a equations for a diprotic acid, except that [H" ] would be replaced by [NH3], the AT s would be replaced by the K/s, and the order of P s would be reversed from the order of a s (Po o since they were defined in reverse order. 

Any acid-base equilibrium can be described by a system of fundamental equations. The appropriate set of equations comprises the equilibrium constant (or mass law) relationships (which define the acidity constants and the ion product of water) and any two equations describing the constitution of the solution, for example, equations describing a concentration and an electroneutrality or proton condition. Table 3.6 gives the set of equations and their mathematical combination for pure solutions of acids, bases, or ampholytes in mono-protic or diprotic systems. 

A salt is defined as a compound formed when the hydrogen of an acid is completely or partially replaced by a metal (Table 18.4). If all the hydrogen is replaced, a normal salt is formed if the hydrogen is not completely replaced, then an acidic salt is formed. Acid salts can only be formed by diprotic and triprotic acids monoprotic acids can only form normal salts. 

What are diprotic and triprotic acids List an example of each. Define the acid ionization constant and explain its significance. Write an equation for the autoionization of water and an expression for the ion product constant for water (Ky,). What is the value of a at 25 °C ... 

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