Chapter 4, Problem 4.36QP

Interpretation Introduction

Interpretation: The volume of the water added to the solution, the initial volume and the initial concentration of the solution of chromium ion is given. The percent decrease in the absorbance on dilution is to be determined.

Concept introduction: The final concentration of the solution is calculated as,

$\text{Final}\text{molar}\text{concentration}=\frac{\text{Initial}\text{molar}\text{concentration}\times \text{Initial}\text{volume}}{\text{Final}\text{volume}}$

The absorbance of the solution is given by the formula,

$\text{Absorbance}=\text{Molar}\text{absorptivity}\times \text{Path}\text{length}\times \text{Molar}\text{concentration}$

Thus, absorbance is directly proportional to the concentration of the solution for the given path length.

Therefore,

$\frac{\text{Final}\text{concentration}}{\text{Initial}\text{concentration}}=\frac{\text{Absorbance}\text{of}\text{final}\text{concentration}}{\text{Absorbance}\text{of}\text{initial}\text{concentration}}$

The percent decreases in absorbance is calculated by the formula,

$\text{Percent}\text{decrease}\text{in}\text{absorption}=\frac{\text{Initial}\text{concentration}-\text{Final}\text{concentration}}{\text{Initial}\text{concentration}}\times 100$

To determine: The percent decrease in the absorbance on dilution of the solution of chromium ion.