3. An indicator is a dye whose spectrum changes with pH. Consider the following data for theabsorption spectrum of an indicator (pK = 4) in its ionized and nonionized form.InH+ → In + H*Molar absorptivity, ɛ(M1.cm1)InH+(nm)In40010,00042015,0002,0004408,0008,00046012,0004803,000The absorbance of the indicator solution is increased in a 1-cm cell and found to be400420440460480(nm)A0.250 0.425 0.400 0.300 0.075a. Calculate the pH of the solution. [4.0]b. Calculate the absorbance of the solution at 440 nm and pH 6.37 for the same total indicatorconcentration. [0.400]c. If you want to measure the quantum yield of fluorescence of In and H* independently,what wavelength would you choose for exciting In H+? For exciting In? Why?

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3. An indicator is a dye whose spectrum changes with pH. Consider the following data for the absorption spectrum of an indicator (pK = 4) in its ionized and nonionized form. InH* + In + H* Molar absorptivity, ɛ (M1.cm-1) InH (nm) In 400 10,000 15,000 8,000 420 2,000 8,000 12,000 3,000 440 460 480

3. An indicator is a dye whose spectrum changes with pH. Consider the following data for the absorption spectrum of an indicator (pK = 4) in its ionized and nonionized form. InH* + In + H* Molar absorptivity, ɛ (M1.cm-1) InH (nm) In 400 10,000 15,000 8,000 420 2,000 8,000 12,000 3,000 440 460 480

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter13: An Introduction To Ultraviolet-visible Molecular Absorption Spectrometry

Section: Chapter Questions

Problem 13.11QAP: The equilibrium constant for the conjugate acid-base pair HIn+H2OH3O++In is 8.00 10-5. From the...

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Question

3. An indicator is a dye whose spectrum changes with pH. Consider the following data for the
absorption spectrum of an indicator (pK = 4) in its ionized and nonionized form.
InH+ → In + H*
Molar absorptivity, ɛ
(M1.cm1)
InH+
(nm)
In
400
10,000
420
15,000
2,000
440
8,000
8,000
460
12,000
480
3,000
The absorbance of the indicator solution is increased in a 1-cm cell and found to be
400
420
440
460
480
(nm)
A
0.250 0.425 0.400 0.300 0.075
a. Calculate the pH of the solution. [4.0]
b. Calculate the absorbance of the solution at 440 nm and pH 6.37 for the same total indicator
concentration. [0.400]
c. If you want to measure the quantum yield of fluorescence of In and H* independently,
what wavelength would you choose for exciting In H+? For exciting In? Why?

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