Concentration calculating with base-ionization constants

In contrast to the previous problem, in which strong acid or base was added, we can assume that the pH is not changed by addition of the phosphoric acid, especially since this solution was previously well buffered with respect to the very small amount of H3PO4 added. Then, if [H ] is fixed, the ratio of two of the desired concentrations can be calculated from each of the ionization constant equations. 

The calculation for the ionization of a weak base parallels that used with weak acids in Examples 17.2 and 17.3 you write the equation, make a table of concentrations (Step 1), set up the equilibrium-constant equation for Kj, (Step 2), and solve for x = [OH ] (Step 3). Assume the self-ionization of water can be neglected. You obtain [HsO ], and then the pH, by solving K = [H30 ][OH ]. 

In these equations, HA symbolizes a weak acid and A symbolizes the anion of the weak acid. The calculations are beyond our scope. However, we can correlate the value of the equilibrium constant for a weak acid ionization, Ka, with the position of the titration curve. The weaker the acid, the smaller the IQ and the higher the level of the initial steady increase. Figure 5.2 shows a family of curves representing several acids at a concentration of 0.10 M titrated with a strong base. The curves for HC1 and acetic acid (represented as HAc) are shown, as well as two curves for two acids even weaker than acetic acid. (The IQ s are indicated.)... 

General models of the electron-capture process are based on the kinetic model of Wentworth and co-workers [254,293,295,298,313-315]. The ionization chamber is treated as a homogeneous reactor into which electrons are continuously introduced at a constant rate and electron-capturing solutes are added at a variable rate in a constant flow of carrier gas. The major consumption of electrons is via electron capture and recombination with positive ions. The model can be expanded to allow for the presence of electron-capturing contaminants and the formation of excited state negative ions. The kinetic model provides a reasonable explanation of the influence of pulse sampling conditions and temperature on the detector response, but exactly calculated solutions are rare. Again, this is because the necessary rate constants are usually unavailable, and the identity and relative concentration of all species present in the detector are uncertain. The principal reactions can be summarized as follows ... 

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