Treatment of ammonia with phenol in the presence of hypochlorite yields indophenol, a blue product that absrobs light at 625 nm, which can be used for the spectrophotometric determination of ammonia. ocr -OH • NH, indophenol anion To determine the ammonia concentration in a sample of lake water, three samples are prepared. In sample A, 10.0 ml of lake water is mixed with 5 mL of phenol solution and 2 mL of sodium hypochlorite solution, and diluted to 25.0 mL in a volumetric flask. In sample B, 10.0 mL of lake water is mixed with 5 mL of phenol solution, 2 mL of sodium hypochlorite solution, and 2.50 ml of a 5.50 x 104 M ammonia solution, and diluted to 25.0 mlL. Sample C is a reagent blank. It contains 10.0 mL of distilled water, 5 mL of phenol solution, and 2 mL of sodium hypochlorite solution, diluted to 25.0 mL. The absorbance of the three samples is then measured at 625 nm in a 1.00 cm cuvette. The results are shown in the table. Absorbance Sample (625 nm) A 0.401 0.648 0.045 What is the molar absorptivity (e) of the indophenol product? c = 4.5 x10 M'cm What is the concentration of ammonia in the lake water? [NH, luke water 22 x10-4 Incorrect

Treatment of ammonia with phenol in the presence of hypochlorite yields indophenol, a blue product that absrobs light at 625 nm, which can be used for the spectrophotometric determination of ammonia. ocr -OH • NH, indophenol anion To determine the ammonia concentration in a sample of lake water, three samples are prepared. In sample A, 10.0 ml of lake water is mixed with 5 mL of phenol solution and 2 mL of sodium hypochlorite solution, and diluted to 25.0 mL in a volumetric flask. In sample B, 10.0 mL of lake water is mixed with 5 mL of phenol solution, 2 mL of sodium hypochlorite solution, and 2.50 ml of a 5.50 x 104 M ammonia solution, and diluted to 25.0 mlL. Sample C is a reagent blank. It contains 10.0 mL of distilled water, 5 mL of phenol solution, and 2 mL of sodium hypochlorite solution, diluted to 25.0 mL. The absorbance of the three samples is then measured at 625 nm in a 1.00 cm cuvette. The results are shown in the table. Absorbance Sample (625 nm) A 0.401 0.648 0.045 What is the molar absorptivity (e) of the indophenol product? c = 4.5 x10 M'cm What is the concentration of ammonia in the lake water? [NH, luke water 22 x10-4 Incorrect

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

Chapter14: Applications Of Ultraviolet-visible Molecular Absorption Spectrometry

Section: Chapter Questions

Problem 14.10QAP: The acid-base indicator HIn undergoes the following reaction in dilute aqueous solution:...

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A 5.3 × 10-2 M solution is to be used to prepare a series of five 100 mL solutions of varying concentration for use in creating a calibration curve for a spectrophotometric experiment. Determine the concentrations of each of the five dilutions if 10 mL aliquots of the current solution is used for V1.
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).
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0 The acid-base indicator HIn undergoes the following reaction in dilute aqueous solution:HIn color1 m H1 1 In2color2The following absorbance data were obtained for a 5.00 3 1024M solution of HIn in 0.1 M NaOH and0.1 M HCl. Measurements were made at wavelengths of 485 nm and 625 nm with 1.00-cm cells.0.1 M NaOH A485 5 0.075 A625 5 0.9040.1 M HCl A485 5 0.487 A625 5 0.181In the NaOH solution, essentially all of the indicator is present as In2; in the acidic solution, it is essentiallyall in the form of HIn.(a) Calculate molar absorptivities for In2 and HIn at 485 and 625 nm.(b) Calculate the acid dissociation constant for the indicator if a pH 5.00 buffer containing a small amountof the indicator exhibits an absorbance of 0.567 at 485 nm and 0.395 at 625 nm (1.00-cm cells).(c) What is the pH of a solution containing a small amount of the indicator that exhibits an absorbance of0.492 at 485 nm and 0.245 at 635 nm (1.00-cm cells)?(d) A 25.00-mL aliquot of a solution of purified weak…
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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.