A caffeine sample was diluted by a factor of 100 and UV-Vis spectra of diluted solution...
A caffeine sample was diluted by a factor of 100 and UV-Vis spectra of diluted solution showed Absorbance of 0.240 at 275nm. The concentration of diluted sample was determined as 2.76 × 10−2 mMol. What is the Molar Absorptivity (e) of caffeine at 275nm in dilute and in concentrated solution? Consider thickness of a cuvette – 1cm.
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A caffeine sample was diluted by a factor of 100 and UV-Vis
spectra of diluted solution...
A caffeine sample was diluted by a factor of 1000 and UV-Vis spectra of diluted solution...
A caffeine sample was diluted by a factor of 1000 and UV-Vis spectra of diluted solution showed Absorbance of 0.0340 at 275nm. The concentration of diluted sample was determined as 2.76 × 10-5 Mol. What is the Molar Absorptivity (e) of caffeine at 275nm in both the diluted and concentrated solutions? Consider thickness of a cuvette – 1cm.
(10 pts) The iron content of a well water sample is determined by UV-Vis spectroscopy. A...
(10 pts) The iron content of a well water sample is determined by UV-Vis spectroscopy. A 10.00 mL aliquot of well water is transferred to a 100.0-mL volumetric flask and 20 mL of 0.10 M nitric acid is added to oxidize iron (II) to iron (II). Next 30 mL of a 0.1 M sodium thiocyanate solution is added to form the deep red complex iron (II) thiocyanate. The solution is diluted to volume with DI water. A reagent blank is...
need help on these Suppose you obtained the following data from two standard solutions of known...
need help on these
Suppose you obtained the following data from two standard solutions of known concentrations using a UV-Vis spectroscope: Analysis # Conc. (mg/L) 8.00 20.00 Absorbance (at 255 nm) 0.160 0.390 What is the concentration (in mg/L) of an unknown solution with an absorbance of 0.200 at 255 nm 10 points)? The unknown solution contains the same analyte as the standard solution does (Assume a path length of 1cm). 10. You prepared a stock solution by dissolving a...
(10 pts total) You are going to collect UV-Vis spectra of an unknown solution of beta...
(10 pts total) You are going to collect UV-Vis spectra of an unknown solution of beta carotene (structure given below) dissolved in hexane. a. (5 pts) You have a choice between a quartz cuvette or a Thallium Bromoiodide (KRS-5) cuvette? Which should you choose and why? The following chart may be useful. KRISTIILTH 100 30000 1000 3000 Wavelength, 0 1000 b. (5 pts) How would taking the spectrum in ethanol affect your spectrum? Explain.
An unknown amount of a compound with a molecular mass of 270.93 g/mol is dissolved in...
An unknown amount of a compound with a molecular mass of 270.93 g/mol is dissolved in a 10-mL volumetric flask. A 1.00-mL aliquot of this solution is transferred to a 25-mL volumetric flask and e water is added to dilute to the mark. The absorbance of this diluted solution at 339 nm is 0.517 in a 1 cm cuvette. The molar absorptivity for this compound at 339 nm is esso- 5835 M-1cm-1 (a) What is the concentration of the compound...
Table 1. Concentrations of [Fe(Phen),1?, M, in water and UV- vis absorbance values recorded at 2...
Table 1. Concentrations of [Fe(Phen),1?, M, in water and UV- vis absorbance values recorded at 2 -505 nm. Concentration of [Fe(Phen)/, M Absorbance 9.500 x 10 0.999 4.250 x 10 0.480 0.219 2.125 10% 1.063 x 10 0.104 0.000 0.003 Table 2. UV-vis absorbance values of [Fe(phen)]* held at 35 °C after mixing with H SO, and recorded at 5 minute intervals (in water at max = 505 nm). Time (minutes) Absorbance 0.997 0.935 0.877 0.823 0.772 0.724 0.680 0.638...
To analyze the chromium in an unknown sample 1.5623 f of the sample was pretreated and...
To analyze the chromium in an unknown sample 1.5623 f of the sample was pretreated and diluted to the exact 100 mL mark in a volumetric flask. Two 20.0 mL samples of this solution were taken. In the first sample, a Cr-EDTA complex is developed and sufficient water is added to give a total volume of 100.0 mL. In the second sample, 10.0 mL of Cr(III) standard solution at to concentration of 15 mM was added before developing the Cr-EDTA...
A, What does the UV-Vis spectrophotometer measure? What is Beer’s Law (you might have to look...
A, What does the UV-Vis spectrophotometer measure? What is Beer’s Law (you might have to look it up) and how does it relate to data collected from a spectrophotometer? B, What is a sample blank? What it is it used for in this experiment? C, What does the addition of NH3(aq) do to the copper(II) solution? If you don’t know because you haven’t yet done the experiment, make an educated guess. (Think about what the NH3 does chemically and what...
Glucose in biological material may be determined by reaction with o-toluidine in 6% glacial acetic acid...
Glucose in biological material may be determined by reaction with o-toluidine in 6% glacial acetic acid at 100 C, after deproteinization with 3% (w/v) trichloroacetic acid, forming a 1:1 glucose-o-toluidine complex that is blue-green in colour and that absorbs radiation at 630 nm and 635 nm. The reagent is stable for many months at room temperature, and the reaction follows Beer's Law over a very wide range of concentrations. A standard glucose sample containing 100.0 mg/dL was reacted with excess...
Glucose in biological material may be determined by reaction with o-toluidine in 6% glacial acetic acid...
Glucose in biological material may be determined by reaction with o-toluidine in 6% glacial acetic acid at 100 C, after deproteinization with 3% (w/v) trichloroacetic acid, forming a 1:1 glucose-o-toluidine complex that is blue-green in colour and that absorbs radiation at 630 nm and 635 nm. The reagent is stable for many months at room temperature, and the reaction follows Beer's Law over a very wide range of concentrations. A standard glucose sample containing 100.0 mg/dL was reacted with excess...
(10 pts) The iron content of a well water sample is determined by UV-Vis spectroscopy. A 10.00 mL aliquot of well water is transferred to a 100.0-mL volumetric flask and 20 mL of 0.10 M nitric acid is added to oxidize iron (II) to iron (II). Next 30 mL of a 0.1 M sodium thiocyanate solution is added to form the deep red complex iron (II) thiocyanate. The solution is diluted to volume with DI water. A reagent blank is...
need help on these
Suppose you obtained the following data from two standard solutions of known concentrations using a UV-Vis spectroscope: Analysis # Conc. (mg/L) 8.00 20.00 Absorbance (at 255 nm) 0.160 0.390 What is the concentration (in mg/L) of an unknown solution with an absorbance of 0.200 at 255 nm 10 points)? The unknown solution contains the same analyte as the standard solution does (Assume a path length of 1cm). 10. You prepared a stock solution by dissolving a...
(10 pts total) You are going to collect UV-Vis spectra of an unknown solution of beta carotene (structure given below) dissolved in hexane. a. (5 pts) You have a choice between a quartz cuvette or a Thallium Bromoiodide (KRS-5) cuvette? Which should you choose and why? The following chart may be useful. KRISTIILTH 100 30000 1000 3000 Wavelength, 0 1000 b. (5 pts) How would taking the spectrum in ethanol affect your spectrum? Explain.
An unknown amount of a compound with a molecular mass of 270.93 g/mol is dissolved in a 10-mL volumetric flask. A 1.00-mL aliquot of this solution is transferred to a 25-mL volumetric flask and e water is added to dilute to the mark. The absorbance of this diluted solution at 339 nm is 0.517 in a 1 cm cuvette. The molar absorptivity for this compound at 339 nm is esso- 5835 M-1cm-1 (a) What is the concentration of the compound...
Table 1. Concentrations of [Fe(Phen),1?, M, in water and UV- vis absorbance values recorded at 2 -505 nm. Concentration of [Fe(Phen)/, M Absorbance 9.500 x 10 0.999 4.250 x 10 0.480 0.219 2.125 10% 1.063 x 10 0.104 0.000 0.003 Table 2. UV-vis absorbance values of [Fe(phen)]* held at 35 °C after mixing with H SO, and recorded at 5 minute intervals (in water at max = 505 nm). Time (minutes) Absorbance 0.997 0.935 0.877 0.823 0.772 0.724 0.680 0.638...
To analyze the chromium in an unknown sample 1.5623 f of the sample was pretreated and diluted to the exact 100 mL mark in a volumetric flask. Two 20.0 mL samples of this solution were taken. In the first sample, a Cr-EDTA complex is developed and sufficient water is added to give a total volume of 100.0 mL. In the second sample, 10.0 mL of Cr(III) standard solution at to concentration of 15 mM was added before developing the Cr-EDTA...
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