3. Using Equation 18-5 and the pKIn value you found, determine the ratio [In-]/[HIn] at the pH in the middle of the range you studied (i. e., pH = 6.0 for bromocresol purple, pH = 7.0 for bromothymol blue, and pH = 7.7 for phenol red). Show how you accomplished this. Draw a conclusion about the relative concentrations of In - and HIn at pH values very close to the pKIn of the indicator.

Question

Chemistry

Lauryn Dillon

20 October, 19:56

3. Using Equation 18-5 and the pKIn value you found, determine the ratio [In-]/[HIn] at the pH in the middle of the range you studied (i. e., pH = 6.0 for bromocresol purple, pH = 7.0 for bromothymol blue, and pH = 7.7 for phenol red). Show how you accomplished this. Draw a conclusion about the relative concentrations of In - and HIn at pH values very close to the pKIn of the indicator.

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Answers (1)

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Margaret Shields · Answer 1

[In-] / [HIn] = [KIn] / [H3O+]

Use the values of PkIN = 7.1,

KIN=8.14E-8, and

[H3O+] = 10E-7

To plug them in as follows:

(8.14E-8) / (10E-7) = 0814, thus shows a very close ratio 1 to 1