Ionic strength, Color Plate

Figure 8-1 Student data showing that the equilibrium quotient of concentrations for the reaction Fe3 + SCN Fe(SCN)21 decreases as potassium nitrate is added to the solution. Color Plate 3 shows the fading of the red color of Fe(SCN)2 after KN03 has been added. Problem 13-11 gives more information on this chemical system. [From R. J. Stolzberg, "Discovering a Change in Equilibrium Constant with Change in Ionic Strength," J. Chem. Ed. 1999, 76.640.]...

To demonstrate the effect of ionic strength on the dissociation reaction, mix 300 mL of 1 mM FeCl3 with 300 mL of 1.5 mM NH4SCN or KSCN. Divide the pale red solution into two equal portions and add 12gofKN03 to one of them to increase the ionic strength to 0.4 M. As KN03 dissolves, the red Fe(SCN)2+ complex dissociates and the color fades (Color Plate 3). 

Color Plate 3 Effect of Ionic Strength on Ionic Dissociation (Demonstration 8-1)... 

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See also in sourсe #XX -- [ , ]

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