(a)
Interpretation:
The ligand-to-metal ratio in the product should be determined.
Concept introduction:
In the method of continuous variation, cation and ligand solutions which have same concentration are mixed in such a way that total number of moles of reactants and the total volume of each mixture are constant. But the mole ratio varies. Then the absorbance of the mixture is measured and absorbance is corrected. The corrected absorbance is plotted against volume fraction of one reactant. A maximum or a minimum occur at metal to ligand volume ratio equals to the combined ratio of metal to ligand.
(b)
Interpretation:
Average molar absorptivity of the complex and its uncertainty should be calculated.
Concept introduction:
In the method of continuous variation, cation and ligand solutions which have same concentration are mixed in such a way that total number of moles of reactants and the total volume of each mixture are constant. But the mole ratio varies. Then the absorbance of the mixture is measured and absorbance is corrected. The corrected absorbance is plotted against volume fraction of one reactant. A maximum or a minimum occur at metal to ligand volume ratio equals to the combined ratio of metal to ligand.
(c)
Interpretation:
Kf for the complex should be determined
Concept introduction:
In the method of continuous variation, cation and ligand solutions which have same concentration are mixed in such a way that total number of moles of reactants and the total volume of each mixture are constant. But the mole ratio varies. Then the absorbance of the mixture is measured and absorbance is corrected. The corrected absorbance is plotted against volume fraction of one reactant. A maximum or a minimum occur at metal to ligand volume ratio equals to the combined ratio of metal to ligand.
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Chapter 14 Solutions
Principles of Instrumental Analysis
- Mixing the chelating reagent B with Ni(II) forms the highly colored NiB22+, whose solutions obey Beer’s lawat 395 nm overa wide range. Provided the analytical concentration of the chelating reagent exceeds that of Ni(II) by a factor of 5 (or more), the cation exists, within the limits of observation, entirely in the form of the complex. Use the accompanying data to evaluate the formation constant Kf for the process Ni2++2BNiB22+arrow_forwardThe absorption coefficient of a glycogen-iodine complex is 0.20 at light of 450 nm. What is the concentration when the transmission is 40 % in a cuvette of 2 cm?arrow_forward(i) The detection of Mn by graphite furnace atomic absorption spectrometry (GFAAS) is sensitive to the presence of aluminium ions Al3+ which may form refractory compounds such as MnAl2O4. Comment on the possible impact of this compound on the measurements and what action may be taken to minimize this. (ii) Write a brief note on the best practice for the preparation of a calibration curve. (iii) Atomic absorption spectroscopy (AAS) is a powerful technique for the analysis of trace amounts of metals. Describe the two common atomic absorption methods used in the lab with reference to their comparative strengths and weaknesses.arrow_forward
- (b) A. for the octahedral complex [Mn(OH2)6]3+ was measured to be 21000 cm-1. (i) Explain how Aois normally measured for transition metal complexes. [2 MARKS] (ii) P, the pairing energy, for the Mn3+ ion was found to be 28000 cm1. Predict an approximate magnetic moment for the complex [Mn(OH2)6]3+, explaining clearly each step in your reasoning and showing all your workings. [4 MARKS] (iii) Predict approximate magnetic moments for the complexes [MnCl6]³- and [Mn(CN)6] given that f factors for Cl- and CN are 0.78 and 1.70 respectively. [4 MARKS] (iv) Explain in terms of molecular orbitals why the f factor for Cl is much less than that for CN. [4 MARKS]arrow_forward(a) Determine the number and activities of the carbonyl stretching modes of both the cis and trans isomers of L2M(CO)4. (b) Calculate the IR and Raman active carbonyl vibrations for both isomers. (c) Fe(CO)4C12 has IR bands at 2167, 2126 and 1082 cm-1 in CHC13 solution. How would you interpret this spectrum?arrow_forwardIron(III) forms a complex with thiocyanate ion that has the formula Fe(SCN)+2. The complex has an absorption maximum at 580nm. A sample of well water was assayed according to the following scheme: Sample Sample Vol (mL) Oxidizer Fe(ii) (mL) added 2.75ppm KSCN (0.050 M) H20 (mL) Abs @ 580 nm 1 50.00 5.00 5.00 20.00 20.00 .549 2 50.00 5.00 0 20.00 25.00 .231 What is the concentration of Fe in the well water sample?arrow_forward
- Looking at a d6 Tanabe-Sugano diagram needed to assign the electronic transistion that corresponds to (lambda)max off 550 nm. Give that the Racah parameter for the iron complex in this complex is 848 cm^-1, determine the lighand field parameter in cm^-1 for the complex in the spin-state associated with lambda max. complex: [Fe(NH2trz)3]Cl2·2H2Oarrow_forward15. Modeling ligand binding. A ligand is bound to a protein with a spring-like square-law energy e(x), where x is the distance between the ligand and protein as shown in the figure. e(2) = }ca² Protein Ligand (a) For constant (T,V,N), write an expression for the probability distribution p(x) of the ligand separation from the protein. (b) Sketch a plot of p(x) vs x. Write an expression for the average location of the ligand, (x). (d) Write an expression for the second moment of the location of the ligand, (x2). (e) Calculate the average energy, (e) of the system.arrow_forwardThe absorbance values observed during the determination of the complex stoichiometry with the Job method using the spectroscopic method were plotted and the following correct equations were obtained. What is the n value of the compound formed by Fe + 3 and SCN- ions? 1. Line equation: y = 2.6188x + 0.16082. Line equation: y = -2.5963x + 2.7203arrow_forward
- The molar absorptivity (ε) of the FeSCN2+ complex ion is 4700 M-1 · cm-1 at a wavelength of 450 nm. Using a 1-cm sample tube, you measure the absorbance as (2.0x10-1). What is the concentration of FeSCN2+?arrow_forwardA solution containing the complex formed between Bi(III) and thiourea has a molar absorptivity of 9.32 x 103 M-1 cm-1 at 470 nm. (a) Calculate the absorption of a 4.25x10-5 M solution of the complex at 470 nm in a 1-cm cell. (b) What is the molar concentration of the complex in a solution that has the calculated absorption in (a) when measured at 470 nm in a 2.50 cm cell?arrow_forward(b) Consider the infra-red spectrum of the complex [(15-C5H5) Fe(CO)2]2 below and answer the questions which follow: (i) (ii) 2300 (A) 2100 r (B) 1900 1700 Wavenumber (cm-¹) 1500 Draw the structure of the dinuclear complex [(15-C5H5) Fe(CO)2]2. (15-C5H5) is the cyclopentadienyl ligand. Assign the bands (A) and (B) to the CO ligands in your structure drawn. Motivate your answer.arrow_forward
- Principles of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage LearningPrinciples of Modern ChemistryChemistryISBN:9781305079113Author:David W. Oxtoby, H. Pat Gillis, Laurie J. ButlerPublisher:Cengage Learning