5) Confidence interval. Berglund and Wichardt investigated the quantitative determinationof Cr in high-alloy steels using a potentiometric titration of Cr(VI). Before the titration,samples of the steel were dissolved in acid and the chromium oxidized to Cr(VI) usingperoxydisulfate. Shown here are the results (as %w/w Cr) for the analysis of a referencesteel.16.968, 16.922, 16.840, 16.883, 16.887, 16.977, 16.857, 16.728Calculate the mean, the standard deviation, and the 95% confidence interval about themean. What does this confidence interval mean?

The mean (or average) is calculated by adding up all the values and dividing by the number of…

Answered: 5) Confidence interval. Berglund and…

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter13: Titrations In Analytical Chemistry

Section: Chapter Questions

Problem 13.27QAP

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A 3.03-g petroleum specimen was decomposed by wet ashing and subsequently diluted to 500 mL in a volumetric flask. Cobalt was determined by treating 25.00-mL aliquots of this diluted solution as follows: Assume that the Co(II)-ligand chelate obeys Beer’s law, and calculate the percentage of cobalt in the original sample.
A 0.4852g sample of an iron ore was dissolved in acid to the 3+ state, then precipitated as Fe2O3 x H2O. The pp was filtered, washed and calcined to Fe2O3, which gave a weight of 0.2481g. Calculate the Fe % in the sample.
An alloy containing Ni, Fe and Cr was analyzed by a complexation titration using EDTA as titrant. A 0.7176 g sample of the alloy was dissolved in HNO3 and diluted to 250 mL in a flask. A 50.00 mL aliquot of the sample, treated with pyrophosphate to mask Fe and Cr, required 26.14 mL of 0.05831 M EDTA to reach the murexide endpoint. A second 50.00 mL aliquot was treated with hexamethylenetetramine to mask Cr and titration with 0.05831 M EDTA required 35.43 mL to reach the murexide endpoint. Finally, a third 50.00 mL aliquot was treated with 50.00 mL of 0.05831 M EDTA and titrated back to the murexide endpoint with 6.21 mL of 0.06316 M Cu(II). the weight percentages of Ni, Fe and Cr in the alloy.
Construct the octahedral crystal-field splitting diagram for the metal in each species. V(H,O); + Co(CN);- FeCi?- DC Answer Bank 1 1L
1. A sample of feldspar weighing 1.500g is decomposed, and eventually there is obtained a mixture of KCI and NaCi weighing 0.1801 g. These chlorides are dissolved in H20, a 50-mL pipetful of 0.08333 N AGNO3 is added, and the precipitate is filtered off. The filtrate requires 16.47 mL of 0.100ON KCNS, with ferric alum as indicator. Calculate the percentage of K20 in the silicate.
A. What is the characteristic color of ferric ions in solution? B. Why is the titration of the oxalate in the green salt with KMnO4 performed prior to carrying out the redox titration for iron content? (Why can’t you do them the other way – iron first then oxalate?) C. In a titration using 0.02000 M KMnO4 solution, the following data were obtained: Buret readings: FINAL = 15.31 mL INITIAL = 5.02 mL How many moles of KMnO4 were used?
Consider the data for the determination of phosphorus in urine as the phosphomolybdate complex, which has a maximum absorbance at 650 nm. 43 1.2 1 0.8 0.6 0.4 0.2 1 2 3 4 6 conc. of P. Dom Below is the generated titration curve from an external standard calibration method in the analysis of phosphorus in soil. Identify the concentration of phosphorus in a gram of sample that has an absorbance of 0.500 at a wavelength of 650 nm. absorbance
4. The cadmium and lead ions in a 50.00 mL sample required 40.09 mL of a 0.005000 M EDTA for titration. A 75.00 mL portion of the same sample was made basic and treated with excess KCN masking the cadmium as Cd(CN),?. This solution required 21.42 mL of the EDTA for titration. Calculate the concentration of Cd2* and Pb2* in the sample ppm and in M.
The amount of Fe (AW 55.85) in a 0.4891-g sample of an ore was determined by a redox titration with K2Cr2O7 (FW 294.20). The sample was dissolved in HCl and the iron brought into the +2 oxidation state using a Jones reductor. Titration to the diphenylamine sulfonic acid end point required 36.92 mL of 0.02153 M K2Cr2O7. Report the iron content of the ore as %w/w Fe2O3 (FW 159.70). a. 54.46 % b. 12.98 % c. 77.86 % d. 31.45 %
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?
The most intense absorption band in the visible spectrum of [Mn(H,O),]?* is at 24900 cm' and has a molar absorptivity of 0.038 L mol' cm'. What concentration of [Mn(H2O)6J²* would be necessary to give an absorbance of 0.10 in a cell of path length 2.00 cm?
The concentration of EDTA is 2.497mM

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