Chapter 11, Problem 11D.2ST

Interpretation Introduction

Interpretation:

Molar concentration of two substances A and B in a sample has to be determined using the given data.

Concept Introduction:

Electronic spectra are used for analyzing mixtures of absorbing species and for determining its concentration. Molar concentration of mixture of two molecules A and B in a sample can be determined by knowing the total absorbance and measurements at two concentrations.

$\begin{array}{l}\left[\text{A}\right]\text{ = }\frac{{\text{ε}}_{\text{B2}}{A}_1-{\text{ε}}_{\text{B1}}{A}_2}{\left({\epsilon }_{\text{A}1}{\epsilon }_{\text{B}2}-{\epsilon }_{\text{A2}}{\epsilon }_{\text{B1}}\right)\text{L}}\\ \\ \left[\text{B}\right]\text{ = }\frac{{\text{ε}}_{\text{A2}}{A}_2-{\text{ε}}_{\text{A1}}{A}_1}{\left({\epsilon }_{\text{A}1}{\epsilon }_{\text{B}2}-{\epsilon }_{\text{A2}}{\epsilon }_{\text{B1}}\right)\text{L}}\\ \\ \text{Total absorbance}=A_1{\text{ when molar absorption coefficients are ε}}_{\text{A1}}{\text{ε}}_{\text{B1}}{\text{ at λ}}_{\text{1}}\\ \\ \text{Total absorbance}=A_2{\text{ when molar absorption coefficients are ε}}_{\text{A2}}{\text{ε}}_{\text{B2}}{\text{ at λ}}_2\end{array}$