tion 13 of 24 > 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+ solution with an unknown concentration and an absorbance value of 0.179. The slope-intercept form of the equation of the line is y = 4536.6x + 0.0392. The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe3+ concentration of the unknown solution? Iron(III) thiocynate standard curve 1.0 mol/L [Fe**] = 0.5 - 0.0001 0.0002 Fet concentration (M) Absorbance

tion 13 of 24 > 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+ solution with an unknown concentration and an absorbance value of 0.179. The slope-intercept form of the equation of the line is y = 4536.6x + 0.0392. The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe3+ concentration of the unknown solution? Iron(III) thiocynate standard curve 1.0 mol/L [Fe**] = 0.5 - 0.0001 0.0002 Fet concentration (M) Absorbance

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 14.22QAP: Mixing the chelating reagent B with Ni(II) forms the highly colored NiB22+, whose solutions obey...

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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 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+ solution with an unknown concentration and an absorbance value of 0.392. The slope-intercept form of the equation of the line is y = 4538.1x +0.0077. The unknown was analyzed on the same instrument as the standard curve solutions at the same temperature. What is the Fe³+ concentration of the unknown solution? [Fe³+] = mol/L Absorbance Iron(III) thiocynate standard curve 1.0 V 0.5 0.0001 Fe³+ concentration (M) 0 0.0002
Complexometric titrations are generally conducted to determine divalent cations. The most important applications are the titration of calcium and magnesium with EDTA. (a) A supplement tablet containing about 300.00 mg of calcium ion was dissolved, filtered, and diluted to 100.00 ml volume. Several 2.00 ml samples of the total solution were titrated with 0.0100 M EDTA solution. The mean corrected titration volume was 13.65 mL. Calculate the calcium content of the supplement tablet in mg units. (b) A sample of Epsom Salt of mass 0.7567 g was dissolved uniformly in distilled water in a 250.00 mL volumetric flask. Portions of the magnesium ion solution of volume 10.00 mL were titrated using a 0.01000 M solution of EDTA. The mean corrected titration volume was 12.25 ml. Calculate the percentage by mass (% w / w) of the magnesium in the Epsom Salt sample. (c) A 100.00 mL sample of tap water was titrated with 0.0100 M EDTA solution. The mean corrected titration volume was 14.80 mL. Determine…
A potentiometric titration of a 0.278 g sample of FeSO4.7H,O salt, in acidic medium, with a 0.011 M solution of potassium dichromate (K.Cr₂O) was conducted. Cr₂0 + 6 Fe + 14 H →2Cr + 6 Fe" + 7 H₂O The potential is measured with respect to a calomel electrode (E246 mV). Graph 1 represents the measured potential with respect to the volume of added dichromate. Calculate E for the half-reaction: Fe + e-Fe (Show your work using Nernst equation). Hint: Use the graph, to determine, approximately, the equivalence point and mid-point of the titration 700 675 650 625 600 575 550 525 500 475 450 425 400 18 20 22 10 12 14 16 V (K₂Cr₂O7) in mL E (MV) 6 8
Solutions of cobalt (II) ions have a magenta color with a molar absorptivity constant (e) value at 511 nm of 5.87 M-1cm-1. A 0.500 mL sample is transferred from a 50.0 mL stock solution of Co(NO3)2 and diluted with water to a final volume of 7.50 mL. The dilution had an absorbance value at 511 nm in a standard cuvette (1.00 cm light path) of 0.382. Calculate the mass of Co(NO3)2 contained in the original 50.0 mL stock solution.
Treatment of ammonia with phenol in the presence of hypochlorite yields indophenol, a blue product that absrobs light at 625 nm, which çan be used for the spectrophotometric determination of ammonia. gan OCF OH + NH3 indophenol anion To determinè 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 10-4 M ammonia solution, and diluted to 25.0 mL. 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. Sample Absorbance (625 nm) A 0.361 B 0.608 C…
The following data were obtained from the spectrophotometric titration of Cu(II) and Ca(II) in an unknown solution. A 25.00 mL aliquot of the unknown was taken to which 50.0 mL of ethanolamine buffer and 25.0 mL of distilled water were added. The solution was then titrated with standard 0.2508 M EDTA solution. Plot the recorded data, absorbance against volume of EDTA in mL. Correct the absorbance for volume changes. Calculate the number of moles of Ca(II) and Cu(II) in the unknown sample. Vol of Titrant, mL Vol of Titrant, mL Abs Abs 0.0 0.416 12.5 0.886 2.0 0.415 13.0 0.923 4.0 0.409 13.5 0.958 6.0 0.416 14.0 0.979 8.0 0.535 14.5 0.969 10.0 0.690 15.0 0.971 11.0 0.770 15.5 0.964 12.0 0.840
A standard solution contains 100 ppm of Fe, which was found to have an absorbance of 0.151 au at 508 nm after the addition of 1,10-phenanthroline, pH 4 buffer, and hydroxylamine. Then, a water sample treated similarly exhibited an absorbance of 0.109 au. Which of the following statements is true? (A) The Fe concentration of the water sample is higher than 100 ppm. B) The Fe concentration of the water sample is equal to 100 ppm. It is impossible to estimate the Fe content of the water sample from information presented. D) The Fe concentration of the water sample is lower than 100 ppm.
A second calibration standard solution of an iron(III) salicylate complex was prepared in two steps. First, 10.0 mL of a 0.100 M stock solution was added to 90.0 mL of solvent to make 100.0 mL of the first calibration standard solution and, secondly, 80 mL of that first calibration solution plus 20.0 mL of solvent were mixed to make the second calibration standard. What is the concentration of the second calibration standard solution?
10-mL aliquots of an environmental water sample were pipetted into five 50.00-mL volumetric flasks. Exactly 0.00, 5.00, 10.00, 15.00, and 20.00-mL of a standard solution containing 11.1 ppm Fe3+ were added to each, followed by an excess of thiocyanate ion to give the red complex Fe(SCN)2+. After dilution to volume, the instrumental response for each of the five solutions measured with a colorimeter was found to be 0.240, 0.437, 0.621, 0.809, 1.809, respectively. Using Excel and the LINEST function, what was the concentration in the water sample (including error)? [HINT: consider the type of calibration scheme used.]
The un-ionized form of the weak acid HA does not absorb in the visible region. When it ionizes, its conjugate base (A-) absorbs light strongly at 510 nm. The following data were obtained by measuring the absorbance at 510 nm of solutions with a concen- tration of 1.0 x 104 M HA in different pH buffers. pH Absorbance 2.0 0.00 3.0 0.00 4.0 0.00 5.0 0.025 6.0 0.180 7.0 0.480 8.0 0.570 9.0 0.595 10.0 0.595 11.0 0.595 12.0 0.595 What is the approximate pK of HA?
(b) An unknown solution containing 25.00 mL of Ni2+ in dilute HCI is treated with a known excess of 25.00 mL of 0.05382 M EDTA solution. The solution turns yellow when a few drops of indicator are added. The excess unreacted EDTA back titrated with 0.02299 M Zn²*, which requires 17.00 mL to reach the red end point. What is the molarity of Ni2+ in the unknown solution?