When I was a boy, I watched Uncle Wilbur measure the iron content of runoff from his banana ranch. He acidified a 25.0-mL sample with HNO3 and treated it with excess KSCN to form a red complex. (KSCN itself is colorless.) He then diluted the solution to 100.0 mL and put it in a variablepathlength cell. For comparison, he treated a 10.0-mL reference sample of 6.80 3 1024 M Fe31 with HNO3 and KSCN and diluted it to 50.0 mL. The reference was placed in a cell with a 1.00-cm pathlength. Runoff had the same absorbance as the reference when the pathlength of the runoff cell was 2.48 cm. What was the concentration of iron in Uncle Wilbur’s runoff ?

When I was a boy, I watched Uncle Wilbur measure the iron content of runoff from his banana ranch. He acidified a 25.0-mL sample with HNO3 and treated it with excess KSCN to form a red complex. (KSCN itself is colorless.) He then diluted the solution to 100.0 mL and put it in a variablepathlength cell. For comparison, he treated a 10.0-mL reference sample of 6.80 3 1024 M Fe31 with HNO3 and KSCN and diluted it to 50.0 mL. The reference was placed in a cell with a 1.00-cm pathlength. Runoff had the same absorbance as the reference when the pathlength of the runoff cell was 2.48 cm. What was the concentration of iron in Uncle Wilbur’s runoff ?

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter26: Molecular Absorption Spectrometry

Section: Chapter Questions

Problem 26.12QAP

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When I was a boy, I watched Uncle Wilbur measure the iron content of runoff from his banana ranch. He acidified a 25.0-mL sample with HNO3 and treated it with excess KSCN to form a red complex. (KSCN itself is colorless.) He then diluted the solution to 100.0 mL and put it in a variablepathlength cell. For comparison, he treated a 10.0-mL reference sample of 6.80X 1024 M Fe31 with HNO3 and KSCN and diluted it to 50.0 mL. The reference was placed in a cell with a 1.00-cm pathlength. Runoff had the same absorbance as the reference when the pathlength of the runoff cell was 2.48 cm. What was the concentration of iron in Uncle Wilbur’s runoff ?
You wish to measure the iron content of the well water on the new property you are about to buy. You prepare a reference standard Fe3+ solution with a concentration of 5.74×10−4 M. You treat 14.0 mL of this reference with HNO3 and excess KSCN to form a red complex and dilute the reference to 60.0 mL. The diluted reference is placed in a cell with a 1.00‑cm light path. You then take 30.0 mL of the well water, treat with HNO3 and excess KSCN, and dilute to 100.0 mL. This diluted sample is placed in a variable pathlength cell. The absorbance of the reference and the sample solutions match when the pathlength is 1.76 cm. What is the concentration of iron in the well water? For each solution, the zero is set with a blank.
You wish to measure the iron content of the well water on the new property you are about to buy. You prepare a reference standard Fe3+ solution with a concentration of 5.53×10−4 M. You treat 10.0 mL of this reference with HNO3 and excess KSCN to form a red complex and dilute the reference to 45.0 mL. The diluted reference is placed in a cell with a 1.00‑cm light path. You then take 20.0 mL of the well water, treat with HNO3 and excess KSCN, and dilute to 100.0 mL. This diluted sample is placed in a variable pathlength cell. The absorbance of the reference and the sample solutions match when the pathlength is 3.25cm. What is the concentration of iron in the well water? For each solution, the zero is set with a blank.
To measure the iron content of runoff from a ranch a 25.0 mL sample of run off was acidified with HNO3 and treated with excess KSCN to form a red complex. (KSCN itself is colorless.) The solution was then diluted to 100 mL and put into a variable pathlenght cell. For comparison, a 10.0 mL reference sample of 6.80 x 10-4 M Fe3+ was treated with HNO3 and KSCN and diluted to 50.0 mL. The reference was placed in a cell with a 1.00 cm pathlenght. The runoff had the same absorbance as the reference when the pathlenght of the runoff cell was 2.48 cm. What wa the concentraton of iron in the runoff?
A 0.9352g sample of ore containing Fe³+, Al³+ and Sr²+ was dissolved and made up to 500.00 mL. The analysis of metals was performed using complexation volumetry. Initially, an aliquot of 50.00 mL had its pH adjusted to 1.0 and titrated with a standard 0.03145 mol/L EDTA solution, requiring 6.95 mL to reach the end point. Subsequently, another 25.00 mL aliquot was buffered at pH=5 and titrated with the same EDTA solution, requiring 6.24 mL to reach the end point. Finally, a third aliquot of 25.00 mL was titrated at pH=11, requiring 11.10 mL of the same EDTA solution to complete the titration. Given the molar masses: Fe=55.845 g/mol; Al-26.982 g/mol and Sr-87.620 g/mol. a) Determine the percentage of each of the metals in the sample. b) Explain why the change in pH allows the determination of the three ions in this sample.
Iron (III) can be separated from other metals, such as chromium, by extraction into ether froma strong aqueous HCl solution. If 50 mL of aqueous HCl containing 0.25 g of iron(III) is treatedwith 150 mL of ether in a one-shot process, how many milligrams of iron is left in the aqueousphase? Use a value of 50 for the distribution ratio.
A 25.00 mL aliquot of a solution containing Cu2+ and Fe3+ was titrated with 17.08 mL of 0.05095 M EDTA. A second 25.00 mL aliquot of the Cu/Fe mixture was treated with NaF to form a stable iron-fluoride complex. This mixture was then titrated with EDTA and the endpoint volume was found to be 5.47 mL. Calculate the amounts of Cu2+ and Fe3+ in mg/L. Molar mass (g/mol): Fe = 55.85 and Cu = 63.55
Given: You weigh out exactly 0.200 g of Fe(NH4)2(SO4)2·6H2O and dissolve it in the 100.00 mL volumetric flask. You then pipette 2.00 mL of this solution into the 50.00 mL volumetric flask to prepare the stock standard tris-bipyridyl-iron(II) solution. a. Calculate the molar concentration of iron(II) in this solution in the 50.00 mL volumetric flask. (The MW of Fe(NH4)2(SO4)2·6H2O is 392.14 g/mol) (answer a given the information above)
You have been sent to India to investigate the occurence of goiter disease attributed to iodine deficency. As part of of your investigation, you must make field measurements of traces of Iodide(I-) in groundwater. The procedure is to oxidize I- to I2 and convert the I2 into an intensely colored complex with the dye brilliant green in the organic solvent toluene. a) A 3.15x10^-6 M solution of the colored complex exhibited an absorbance of 0.267 at 635nm in a 1.00cm cuvet. A blank solution made from distilled water in place of groundwater had an absorbance of 0.019. Find the molar absroptivity of the colored complex. b)The absorbance of an unknown solution prepared from ground water was 0.175. Find the concentration of the unknown.
You want to determine the amount of iron(III) in acomplex salt. You make a 100.0 mL solution of the complex salt by dissolving 0.0670 g of complex salt with water to the mark on a 100.0 mL volumetric flask. You get an absorbance reading for the iron from the spectrometer of 0.334. The molar absorptivity is determined to be 17605 L/mole∙cm and the pathlength is 1.00 cm. Determine the molarity of iron(III) in solution. Determine the mass percentage of iron(III) in the complex salt.
Why is EDTA complex formation less complete at lower pH?
What is the reason of starting with Co(II) complex instead of Co(III) in experiment of preparation and solution conductivity of [Co(NH3)4CO3] and [Co(NH3)5Cl] Cl2 ?