Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 19: Q3P (page 484)

When are isosbestic points observed and why?

Short Answer

Expert verified

When spectra of two compounds with a constant total concentration cross at any wavelength, the isosbestic points are observed.

Step by step solution

01

Define isosbestic points:

The identified wavelength or frequency will not change at total absorbance of a sample during the chemical reaction or physical change.

02

Determine the observation of isosbestic points:

When spectra of two compounds with a constant total concentration cross at any wavelength, the isosbestic points are observed. Hence, the mixtures that have same total concentration also will have same isosbestic points. The isosbestic points are observed which helps in finding, how one species is converted into other major species.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

The indicator xylenol orange (Table 12-3) forms a complex with Zr(IV)in HCIsolution. Prepare a Job plot from the data in the table and suggest the stoichiometry of the complex (xylenol orange)Zrzx.

The spreadsheet gives the productεbfor four pure compounds and a mixture at infrared wavelengths. Modify Figure 19-4 to solve four equations and find the concentration of each compound. You can treat the coefficient matrix as if it were molar absorptivity because the path length was constant (but unknown) for all measurements.

Now we use Solver to find Kfor the previous problem. The only absorbing species at 332 nmis the complex, so, from Beer’s law [complex]=A/ε(becausepathlength=1.000cm).I2is either free or bound in the complex,so [I2]=[I2]tot-[complex].There is a huge excess of mesitylene, so[mesitylene]≈[mesitylene]tot

K=[complex][l2][mesitylene]=A/ε(l2tot-A/ε)[mestitylene]tot

The spreadsheet shows some of the data. You will need to use all the data. Column A contains [mesitylene] and column B contains [l2]tot. Column C lists the measured absorbance. Guessa value of the molar absorptivity of the complex,ε,incellA7.Then compute the concentration of the complex (=A/ε)in column D. The equilibrium constant in column EisgivenbyE2=[complex]/([I2][mesitylene])=(D2)/((B2-D2)*A2).

should we minimize with Solver? We want to varyεin cell A7 until the values of Kin column E are as constant as possible. We would like to minimize a function like ∑(Ki-Kaverage)2, where Kiis the value in each line of the table and Kaverage is the average of all computed values. The problem with ∑(Ki-Kaverage)2is that we can minimize this function simply by making Kivery small, but not necessarily constant. What we really want is for all the Kito be clustered around the mean value. A good way to do this is to minimize the relative standard deviationof the K, which is (standard deviation)/average. In cell E5we compute the average value of Kand in cell E6the standard deviation. Cell E7contains the relative standard deviation. Use Solver to minimize cell E7by varying cell A7. Compare your answer with that of Problem 19-13.

The figure shows spectra of1.00×10-4MMnO4-,1.00×10-4and an unknown mixture of both, all in1.000‐cm‐path length cells. Absorbances are given in the table. Use the least squares procedure in Figure 19-3 to find the concentration of each species in the mixture.

Visible spectrum ofMnO4-,Cr2O72-, and an unknown mixture containing both ions.

Iodine reacts with mesitylene to form a complex with an absorption maximum at 332 nm in CCl4 solution:

(b)Spectrophotometric data for this reaction are shown in the table.Because[mesitylene]tot>>[I2],we can say that [mesitylene]≈[mesitylene]tot. Prepare a graph ofA/([mesitylene][I2]tot)versusA/[I2]totand find the equilibrium constant and molar absorptivity of the complex.
See all solutions

Recommended explanations on Chemistry Textbooks

Making Measurements

Read Explanation

Organic Chemistry

Read Explanation

Chemical Analysis

Read Explanation

Chemistry Branches

Read Explanation

Inorganic Chemistry

Read Explanation

The Earths Atmosphere

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free