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 13, Problem 13.10QAP
Zinc(II) and the ligand L form a 1:1 complex that absorbs strongly at 600 nm. As long as the molar concentration of L exceeds that of zinc(II) by a factor of 5, the absorbance depends only on the cation concentration. Neither zinc(II) nor L absorbs at 600 nm. A solution that is 1.59 × 10-4 M in zinc(II) and 1.00 × 10-3 M in L has an absorbance of 0.352 in a 1.00-cm cell at 600 nm. Calculate
(a) the percent transmittance of this solution.
(b) the percent transmittance of this solution in a 2.50-cm cell.
(c) the molar absorptivity of the complex.
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Consider the octahedral complex [FeBr6] 4−. In water solution it has an absorption peak at 864 nm with a molar absorptivity (ε) of 3.6 L mol-1 cm-1 .
(a) What is the energy (in wavenumbers, cm-1 ) of the absorption peak? Show all work.
(b) How many valence d electrons does the metal center have? Justify your answer.
(c) How many unpaired electrons per molecule would a magnetic susceptibility experiment predict? What would the S number be for this transition metal center? Justify your answers.
(d) What electronic transition results from absorption of 864-nm light?
(e) Calculate the ligand stabilization energy (in units of ∆o) and units of coulombic (Πc) energy.
(f) How would the ligand field strengths (∆o) of [Fe(NH3)6] 2+ and [Fe(bipy)3] 2+ differ from that of [FeBr6] 4−? Why?
At 580 nm, the wavelength of its maximum absorption, the complex Fe(SCN)2+ has a molar absorptivity of 7.00x103 L mol-1 cm-1. Calculate letter D ONLY
a.) the absorbance of 2.50x10-5 M solution of the complex at 580 nm in 1.00-cm cell. = 0.175
b.) the absorbance of a solution in which the concentration of the complex is twice that in part (a).
c.) the transmittance of the solutions described in parts (a) and (b).
d.) the absorbance of a solution that has half the transmittance of that described in part (a).
a) Identify the ground terms for Fe²* in the case of free ion and octahedral complexes; [Fe(H2O)6]²* and
[Fe(CN)6]+.
b) Write all spin-allowed transitions with their energy terms for the complexes using Tanabe-Sugano
diagram.
c) The absorption spectrum of [Fe(H2O)6]²* shows a maximum at 1000 nm with a shoulder at 1250 nm.
Estimate the value of A, for [Fe(H2O)«]?+ in cm' unit and determine the transition responsible for this
shoulder.
d) Give a comparison on the color of the complexes.
Chapter 13 Solutions
Principles of Instrumental Analysis
Ch. 13 - Prob. 13.1QAPCh. 13 - Prob. 13.2QAPCh. 13 - Prob. 13.3QAPCh. 13 - Prob. 13.4QAPCh. 13 - Prob. 13.5QAPCh. 13 - Prob. 13.6QAPCh. 13 - Prob. 13.7QAPCh. 13 - At 580 nm, which is the wavelength of its maximum...Ch. 13 - Prob. 13.9QAPCh. 13 - Zinc(II) and the ligand L form a 1:1 complex that...
Ch. 13 - The equilibrium constant for the conjugate...Ch. 13 - The equilibrium constant for the reaction...Ch. 13 - Prob. 13.13QAPCh. 13 - Prob. 13.14QAPCh. 13 - Prob. 13.15QAPCh. 13 - Prob. 13.16QAPCh. 13 - Prob. 13.17QAPCh. 13 - Prob. 13.18QAPCh. 13 - Prob. 13.19QAPCh. 13 - Prob. 13.20QAPCh. 13 - Prob. 13.21QAPCh. 13 - Prob. 13.22QAPCh. 13 - Prob. 13.23QAPCh. 13 - Prob. 13.24QAPCh. 13 - Prob. 13.25QAPCh. 13 - Prob. 13.26QAPCh. 13 - Prob. 13.27QAP
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