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Unformatted text preview: appear in yellow whereas in strong basic solutions, most of the indicator will be in the In form, resulting the color to appear in blue. As the pH of a solution containing the indicator changes, the color shifts enabling one to see the changes from acid to base and vice versa. An acid-base indicator can be used to visually indicate the approximate pH of a sample. The approach used in this experiment involves taking advantage of the fact that the acidic and basic forms of the indicator absorb more strongly at different wavelengths. As the pH changes, the relative concentration of each form will change in accordance with the acid dissociation constant of the indicator and the resulting absorbance of each form will also change. The pKa of the indicator is obtained by the graphical analysis of the Absorbance at the wavelength of the maximum absorbance of In versus the pH data....
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- Spring '11