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
To measure the nickel content in steel, the alloy is dissolved in 12 M HCl and neutralized in the presence of citrate ion, which maintains iron in solution. The slightly basic solution is warmed, and dimethylglyoxime (DMG) is added to precipitate the red DMG-nickel complex quantitatively. The product is filtered, washed with cold water, and dried at 110°C. a) If 1.1634 g of steel gives 0.1795 g of precipitate, what percentage of Ni is in the steel?
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.
A Chemist collected a 0.4891-g sample of an ore for Fe determination by a redox titration with K2Cr2O7.The ore was carefully crushed prior to weighing and dissolved in HCl and using a Jones reductor the ironin the sample was brought into the +2 oxidation state. After titration with diphenylamine sulfonic acid,itrequired 36.92 mL of 0.02153 M K2Cr2O7 to reach the end point. Calculate the iron content of the ore as%w/w Fe2O3
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 %
Cerium(IV) is a strong oxidizing agent commonly used in redox titrations. Which of the following statemnt is/are NOT true for cerium(IV)? I.A Ce** standard solution is prepared using primary-standard-grade ammonium hexanitratocerate(IV), (NH4)2Ce(NO3); dissolved in hot hydrochloric acid solution. II. Ce** is yellow and Ce3* is colorless. The color change is abrupt enough that Ce** can serve as its own indicator. III. Ce**/Ce* exists in different formal potential in different acids due to the interaction of the anions part of the acid with Ce** IV. Analysis of many organic analyte such as alcohol, aldehydes can be determined using Ce**by an indirect method involving a technique of back titration of unreacted excess Ce*with standard iron Il titrant O a. 1,11,IV O b. 1, II, III O. I,II O d. II, II, IV O e. I, II, III, IV

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