Principles of Instrumental Analysis
7th Edition
ISBN: 9781305577213
Author: Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher: Cengage Learning
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Chapter 16, Problem 16.2QAP
Interpretation Introduction
(a)
Interpretation:
The force constant for
Concept introduction:
The force constant is defined as the restoring force divide by unit distance by which the bond is stretched out. The force constant is used for the analysis and characteristics of the molecules.
Interpretation Introduction
(b)
Interpretation:
The wavenumber of the absorption band for
Concept introduction:
The wavenumber is defined as the wavelength per unit distance. The wavenumber is generally expressed in
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(b) The UV-visible electronic absorbance spectrum of the following azo dye has
an absorption maximum at 524 nm.
Three Raman excitation wavelengths are available to obtain the spectrum of
this molecule; 406 nm, 514 nm and 785 nm.
Explain as fully as possible, the differences in the spectra that would be
expected using each of these different excitation wavelengths, and why
differences occur. State which wavelength would be the most appropriate,
justify your answer.
NH2
Meo
OMe
N
N-NH
Azo dye
(a) Draw a rough schematic of the series of resonances corresponding to a vibrational transition
for a diatomic. Label the P and R branches, explain what the difference is between them, and
indicate what the spacing is between the resonance lines.
(b) What is the main information about a diatomic molecule that one can obtain from vibrational
and rotational transition frequencies (assuming that the reduced mass is known)?
(hydrogen iodide, the superscripts represent the atomic mass number)
(a) How fast will HI molecules rotate at the quantized rotational state with the rotational quantun number J of 2, given the bond length of 0.161 nim?
(b) Calculate the effective force constant of the vibrational mode of HI at a wavenumber of 2300 cm' measured by infrared absorption spectrum.
(c) HI has the bond energy of 3.06 eV. Applying the parabolic approximation to estimate the longest distance in which H and I atoms can be stretched before the dissociation of the molecular bond
Chapter 16 Solutions
Principles of Instrumental Analysis
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- state which of the following molecules show a pure rational microwave absorption spectrum and explain why (a) H2O (b) CO2 (c) NH3 (d) N2O (e) Benzene (f) Cl2arrow_forwardA hydrogen fluoride molecule shows a vibrational wavenumber of 4141 cmt. (a) Determine the force constant of the HF bond. Show all working. (b) Predict the vibrational wavenumber of deuterium fluoride (?HF). ASsume that the force constant of 2HF is the same as that for HF. Show all working. (c) Briefly explain why HF is infrared active.arrow_forward(i) Explain how the mass of the particle(s) involved affects the separation between energy levels in quantum mechanics. (ii) Explain why the sensitivity of an NMR experiment is affected by the strength of the applied magnetic field. (iii) Explain why, to a good approximation, rotational and vibrational transitions do not change the energies of electrons.arrow_forward
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