Principles of Instrumental Analysis
7th Edition
ISBN: 9781305577213
Author: Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher: Cengage Learning
expand_more
expand_more
format_list_bulleted
Question
Chapter 17, Problem 17.9QAP
Interpretation Introduction
Interpretation:
The equation of the calibration curve should be determined and the concentration of the three unknown samples should be determined.
Concept introduction:
A calibration curve or standard curve is a method used in
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
Thienothiophene and sexithiophene are conjugated molecules used in printed organic electronics. A chlorobenzene solution of equal concentrations of the two molecules was prepared and its absorbance was recorded with a 0.01 cm sample cell to give 0.88 % transmittance (T) at 400 nm. Calculate the concentration of each of the molecules given that the molar absorption coefficient of the thienothiophene is 23,000 L.mol-1cm-1 and the sexithiophene is 34,000 L.mol-1cm-1. Remember that absorbance is additive.
For a molecule in solution for which the absorption A at λ max is measured as 0.85 for a concentration of 0.3 mol m-3 in a spectrometer cell of path length 1 cm, the molar absorptivity (ɛ), in m2 mol-1, is which of the following?
2.8
56
0.3
2.8 x 102
Exactly 10.00-mL aliquots of a solution containing phenobarbital were measured into 50.00-mL volumetric flasks and made basic with KOH. The following volumes of a standard solution of phenobarbital containing 2.000μg/mL of phenobarbital were then introduced into each flask and the mixture was diluted to volume: 0.000, 0.500, 1.00, 1.50, 2.00 mL. The fluorescence of each of these solutions was measured with a fluorimeter, which gave values of 3.26, 4.80, 6.41, 8.02, 9.56, respectively.
a. plot the data.
b. derive a least squares equation for the data plotted in (a).
c. find the concentration of phenobarbital from the equation in (b).
d. calculate a standard deviation for the concentration obtained in (c).
Chapter 17 Solutions
Principles of Instrumental Analysis
Knowledge Booster
Similar questions
- Standard solutions of a chemical species with different concentrations are analyzed using a UV-Vis spectrophotometer. The absorbance values obtained are plotted against concentration and the slope of the drawn calibration line is calculated as 55400. Since a 0.5 cm cuvette is used in this analysis, calculate the molar absorptivity coefficient of the analyzed species.arrow_forward10.Which of the following statements regarding double beam spectrophotometers is NOT true? Why? a.The reference beam allows for automatic correction for source intensity fluctuations. b. Comparison of the power emerging from the sample and reference beams determines absorbance and transmittance. c. The reference beam allows for automatic correction for detector drift d. The reference beam is created using a stationary mirror. e. The reference beam is created using a rotating mirror.arrow_forwardThe absorbances of solutions containing K2CrO4 in 0.05 M KOH were measured in a 1.0-cm cell of 375 nm. The following results were obtained: Calculate the linear equation of the calibration curve.arrow_forward
- Explain why an internal standard is required during sample preparation in quantitative analysis when using atomic spectroscopy?arrow_forwardWhat is the extinction coefficient for the following absorbances? 1. 3.000 2. 2.022 3.1.2025 4. 0.824 Would the units be in µmoles/mL)^-1 cm^-1arrow_forwardAbsorption bands in the region of 1600-1700 cm-1 are often used for quantification of caffeine. What does the bands in this region refer to?arrow_forward
- What is the molar extinction coefficient at 625 nm for this copper (II) acetate solution? How was it determined? Can the calibration curve be used to accurately predict the absorbance of 0.0150 M copper (II) acetate solution at 625? Why or why not?arrow_forwardChemistry Atomic absorption analysis of Zn gave a calibration best fit line of A=0.670(ppm Zn) The detection limit was determined for this analysis using a 0.020 ppm Zn solution. The standard deviation of the absorbances for 11 samples of the solution was found to be 1.560 x 10-3 and the slope of the calibration curve was 0.026. Calculate the detection limit, Cq, (in units of ppm) for this instrument. Give your answer to 3 places after the decimal place.arrow_forwardChloroform is used as an internal standard in the determination of the pesticide deltamethrin. To calibrate the method a mixture of 0.500 mM of chloroform and 0.800 mM of deltamethrin which produced signals of 15.3 (w.a.) and 10.1 (w.a.) for chloroform and deltamethrin, respectively. To prepare the sample, 10.00 mL of a sample of unknown concentration of deltamethrin and 10.10 μL of pure chloroform (FW = 119.39 g/mol, ρcloroformo = 1.484 g/L) is homogenized and diluted with water to the 100.00 mL mark in a volumetric flask. After preparing the sample, the observed signals of 30.0 (a.u.) and 20.7 (a.u.) for chloroform and deltamethrin, respectively, are observed. 1. Determine the response factor (K) for the method. 2.Determine the millimolar (mM) concentration of chloroform added to the sample. Remember that the final volume of the solution is 100.00 mL. 3.Determine the millimolar (mM) concentration of deltamethrin in the sample. 4.If the concentration of deltamethrin should not…arrow_forward
- The molar absorptivity for Blue #1 dye is 1.30105 M‒1 ·cm‒1 at 629 nm. Calculate the expected absorbance of solution of Blue #1 with a concentration of 4.50×10–6M when measured at 629 nm in a 1.50 cm cell.arrow_forwardBenzophenone is an aromatic ketone, being an important compound. in organic photochemistry, perfumery and in organic synthesis. benzophenone has an optical absorption band at 340 nm (Λ max) that changes to longer wavelengths when the composite is placed in a polar solvent. What is the prediction you can make of the transition type responsible for this optical absorption and justify your answerarrow_forwardInductively coupled plasma–optical emission spectrometry (ICP-OES) was used for the determination of cadmium using indium as an internal standard. A solution containing 2.15 ppm Cd2+ and 5.76 ppm In3+ gave signals of 19,291 and 37,190 counts for cadmium and indium, respectively. A 0.01652 g sample was dissolved in acid and quantitatively transferred to a 250.0 mL volumetric flask. A 1.00 mL aliquot of 264.5 ppm In3+ was added and the flask was diluted to volume with deionized water. ICP-OES analysis of the sample solution gave signals of 31,109 and 118,941 counts for cadmium and indium, respectively. What was concentration of the Cd2+ in the sample? Give answer all questions with explanationarrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Principles of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage Learning
Principles of Instrumental Analysis
Chemistry
ISBN:9781305577213
Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher:Cengage Learning