Guntelberg approximation

It should be noted that, for solutions of ionic strength < 10 mol L , either Equation (3.4) or the Giintelberg approximation (3.5), which incorporates an average value of 3 for ai, can be used. The Guntelberg approximation is particularly useful in calculations where a number of ions are present in solution or when values of the ion size parameter are poorly defined. 

The simplest example of the application of graphical representation of equilibrium data is that for acid-base equilibria involving a monoprotic acid, such as the acid HA, for which the equilibrium expression for solution in water may be written in terms of a concentration acidity constant, that is, an acidity constant valid at the appropriate temperature and corrected for activity by, f3r example, the Guntelberg approximation ... 

In order to compute the formal potential we first consider the activity correction of the Fe -Fe electrode. Using the Guntelberg approximation, is corrected to... 

Calculate [H ][HP0/ ]/[H2P04 l, called K, using the Guntelberg approximation of the DeBye-Hiickel law. 

Guntelberg proposed a simple equation for the hydrated ion size by assuming BRmin = 1, since ions are approximately 1 A and B is on the order of 10s cm... 

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