In Section 6.2d, we saw that pK a of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base. UV–vis spectroscopy can be used to measure the relative concentrations involved if the acid or conjugate base absorbs UV–vis light. With this in mind, suppose that a particular acid has λ max of 312 nm. The given figure shows the absorbance at that wavelength as a function of pH . pK a of the acid is to be determined. Concept introduction: If the given absorbance corresponds to the concentration of acid present, half the absorbance shows the acid which is dissociated in the equal concentration of its conjugate base. pK a of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base.

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Chapter 15, Problem 15.39P

Interpretation Introduction

Interpretation:

In Section 6.2d, we saw that pKa of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base. UV–vis spectroscopy can be used to measure the relative concentrations involved if the acid or conjugate base absorbs UV–vis light. With this in mind, suppose that a particular acid has λmax of 312 nm. The given figure shows the absorbance at that wavelength as a function of pH. pKa of the acid is to be determined.

Concept introduction:

If the given absorbance corresponds to the concentration of acid present, half the absorbance shows the acid which is dissociated in the equal concentration of its conjugate base. pKa of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base.

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In Section 6.2d, we saw that the pK, of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base. UV-vis spectroscopy can be used to measure the relative concentrations involved if the acid or conjugate base absorbs UV-vis light. With this in mind, suppose that a particular acid has a Amax of 312 nm. The figure here shows the absorbance at that wavelength as a function of pH. What is the pk, of the acid? 3 4 6 7 8 10 11 12 pH Absorbance at 312 nm

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