The accuracy of a spectrophotometer can be evaluated by preparing a solution of 60.06-ppm K2Cr2O7 in 0.0050 M H2SO4 and measuring its absorbance at a wavelength of 350 nm using a cell with a pathlength of 1.00 cm. The absorbance should be 0.640. What is the molar absorptivity of K2Cr2O7 at this wavelength?

The accuracy of a spectrophotometer can be evaluated by preparing a solution of 60.06-ppm K2Cr2O7 in 0.0050 M H2SO4 and measuring its absorbance at a wavelength of 350 nm using a cell with a pathlength of 1.00 cm. The absorbance should be 0.640. What is the molar absorptivity of K2Cr2O7 at this wavelength?

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter13: An Introduction To Ultraviolet-visible Molecular Absorption Spectrometry

Section: Chapter Questions

Problem 13.24QAP

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3.) The accuracy of a spectrophotometer is evaluated by preparing a solution of 60.06 ppm K2Cr2O7 and measuring its absorbance at a wavelength of 350 nm in a cell with a pathlength of 1.00 cm. The expected absorbance is 0.640. What is the expected molar absorptivity of K2Cr2O7 at this wavelength?
If the apparent molar absorptivity of cefuroxime sodium is 2.046 × 103 L mol−1 cm−1 in a 1-cm cuvette, at what concentration should the standard and sample solutions be prepared to result to an ideal absorbance value of 0.500? Show your solution.
A spectrophotometric method for the quantitative determination of the concentration ofPb2+ in blood yields an Ssamp of 0.133 for a 1 mL sample of blood that has been diluted to 6 mL. A second sample is spiked with 1 µL of a 1467 ppb Pb2+ standard and diluted to 6 mL, yielding an Sspike of 0.491. Determine the concentration of Pb2+ in the original sample of blood.
What is the absorbance of a 2.33×10−4M2.33×10−4M solution of a compound with a molar absorptivity of 1.05×103M−1cm−11.05×103M−1cm−1 in a 1.00 cm cell?
Suppose that a solution has an absorbance of 0.226 at a wavelength of 450 nm. If the concentration of the solution is 24 μM, what is the value of the molar absorptivity? The data were taken with a standard 1-cm cuvette.
A 131.7 mg sample of powdered Carbamazepine tablets was boiled with ethanol, filtered and then made up to 100 mL with ethanol. 5 mL of this solution was then diluted to 250 mL with ethanol and the absorbance at 285 nm found to be 0.486 in a 1cm path length cell.Calculate the content (% m/m) of Carbamazepine in the powder, taking A(1%, 1 cm) as 490.(State your answer to 1 decimal place and include the units)
The standard curve was made by spectrophotographic analysis of equilibrated iron(III) thiocyanate solutions of known concentration. You are asked to analyze a Fe(SCN)2+Fe(SCN)2+ solution with an unknown concentration and an absorbance value of 0.4150.415 . The slope-intercept form of the equation of the line is ?=4558.4?+0.0147y=4558.4⁢x+0.0147 . The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe3+Fe3+ concentration of the unknown solution?
The measures absorbance of a solution with a pathlength of 1.00 cm is 0.544. If the concentration is 1.40 x 10^-3 M, what is the molar absorptivity for this analyte?
A Dubosq colorimeter consists of a cell of fixed path length and a cell of variable path length. By adjusting the length of the latter until the transmission through the two cells is the same. the concentration of the second solution can be inferred from that of the former. Suppose that a plantdye of concentration 25 μg dm-3 is added to the fixed cell. the length of which is 1.55 em. Then a solution of the same dye. but of unknown concentration. is added to the second cel l. It is found that the same t ransmittance is obtained when the length of the second cel l is adjusted to 1.18 em. What is the concentration of the second solution?
A method for the analysis of Ca2+ in water suffers from an interference in the presence of Zn2+. When the concentration of Ca2+ is 100 times greater than that of Zn2+, an analysis for Ca2+ gives a relative error of +0.5%. What is the selectivity coefficient for this method?
A green solution containing Ni+2 ions absorbs 580 nm light. Undiluted, a sample of this solution sampled in a 1.00 cm diameter cuvette has an absorbance of 0.9765 a.u.. If the molar absorptivity coefficient for Ni+2 is 6.3 x 104 M -1 cm -1 at 580 nm, how much of the original stock Ni+2 solution (in mL) needs to be added to water to create a total dilute solution volume of 10.00 mL that measures an absorbance of 0.146 a.u. at 580 nm? Report your answer to 3 significant figures. Do not include the "mL' unit label in your response
Using the absorbance of [FeSCN]+2 at the wavelength of maximum absorption which you obtained in part B, and the diameter of the tube, obtained in part A,calculate the molar extinction coefficient. given info: Concentration of Fe3+ stock solution, C1 = 0.001 M Volume of stock Fe3+ solution pipetted, V1 = 25mL Concentration of diluted stock solution, C2 = 0.0004 M Volume of Fe2+ solution and KSCN (upon mixing) = 10mL Weight of KSCN = 1g The reaction taking place is given as: The reaction taking place is given as: F e 3+ (aq) + SC N − (aq) ⇔Fe [SCN] 2+ (aq) the concentration of [FeSCN]2+ after the mixing of Fe3+ and SCN- is 2.5 x 10-3 M. Moles of [FeSCN]2+ = 2.5 x 10-5 moles Diameter:1.2cm The wavelength at which maximum absorption takes place is = 480 nm