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 17, Problem 17.11QAP
Interpretation Introduction
Interpretation:
The path length of the cell should be determined.
Concept introduction:
The path length is a distance travelled by the light through a sample of analytical cell. It is used in the infrared spectroscopy. The path length can change the sample absorbance without changing the concentration of the sample.
The wave number is also used to calculate the path length of cell. The wave is reciprocal of wavelength of absorption. It is number of wave per unit distance.
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The molar absorptivity for aqueous solutions of phenol at 211 nm is 6.17 × 103 L cm-1 mol-1.
Calculate the permissible range of phenol concentrations if the transmittance is to be less than 85% and greater than 7% when the measurements are made in 1.00-cm cells.
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?
At 520 nm with a 1.00 cm cell a 8.24 ppm solution of KMnO4 has a transmittance of 0.126. What is the molar absorptivity of KMnO4 at 520 nm?
Chapter 17 Solutions
Principles of Instrumental Analysis
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- 1. A compound has a molar absorptivity of 3.031 x 10° L cm1 mol1. If a 15.00 mm-length cell is used to hold the sample, and a transmittance of 19.53 % is measured, what is the molarity of the compound in solution?arrow_forward3.) 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? 4.) A solution’s transmittance is 35.0%. What is the transmittance if you dilute the solution to half of its initial concentration?arrow_forwardA solution containing 5ppm KMNO4(F.W.159) has a transmittance of 0.360 measured in 1 cm cell at 500 nm. The molar absorptivity of KMNO4 in L mole1 cm 1 is: O 1.1 x 104 1.9 x 104 1.4 x 104 2.7 x 104arrow_forward
- . What is the molar absorptivity when the percent transmittance is 56.2%, the pathlength is 2.00 cm, and the concentration is 0.0000748 M?arrow_forwardFind the concentration of a solution with a transmittance of 0.27 AU and molar absorptivity of 3.65 x 104 M- cm in a 1.00 cm cell.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
- A inorganic compound whose concentrations is 0.013 M in a 1 cm pathlength cell has transmittance of T=8.23%.(i) Find the absorbance (A) and(ii) The molar absorptivity.arrow_forward7) A 25.0 ml sample containing Cu gave an instrument reading of 23.6 units (corrected for a blank). When exactly 0.500 ml of 0.0287M Cu(NO3)2 Was added to the solution,the signal increased to 37.9 units. Calculate the molar concentration of Cu" in the sample +2,arrow_forwardThe molar absorptivity for aqueous solutions of phenol at 211 nm is 6.17 x 103 L cml mol-'. Calculate the permissible range of phenol concentrations if the transmittance is to be less than 85% and greater than 7% when the measurements are made in 1.00-cm cells.arrow_forward
- (a) You measure the percent transmittance of a solution containing chromophore X at 400nm in a 1-cm path length cuvette and find it to be 50%. What is the absorbance of this solution? (b) What is the molar absorptivity of chromophore X if the concentration of X in the solution measured in question (a) is 0.5mM? (c) What is the concentration range of chromophore X that can be assayed if, when using a sample cell of path length 1, you are required to keep the aborbance between 0.2 and 0.8?arrow_forwardA solution containing 4.48 ppm KMnO, had a % transmittance of 30.9% in a 1.00 cm cell at 520 nm. Calculate the molar absorptivity of KMnO, at 520 nm.arrow_forwardSolutions of fluorene (diphenylmethane) in benzene can be analyzed by making use of its absorbanceat 301 nm wavelength. If a solution of fluorene of unknown concentration in benzene exhibits anabsorbance of 0.720 in a 1.00-cm cuvette cell. What is the concentration of fluorene? (Ans. c = 6.55x10 -5 M)arrow_forward
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