The mass percent of Fe in an unknown salt sample was determined using both volumetric and gra vimetric titration. Ten determinations using both methods were performed. Volumetric(% of Fe): 24.22, 23.86, 24.07, 24.49, 24.69, 23.71, 24.28, 24.11, 24.26, 24.10 Gravimetric (% of Fe): 24.35, 24.26, 24.10,24.19, 24.18, 24.32, 24.11, 24.33, 24.17, 24.12 a. Do the two methods give similar standard deviations? b. Do the two methods give similar results for the mass percent of Fe at the 95% confidence level?

The mass percent of Fe in an unknown salt sample was determined using both volumetric and gra vimetric titration. Ten determinations using both methods were performed. Volumetric(% of Fe): 24.22, 23.86, 24.07, 24.49, 24.69, 23.71, 24.28, 24.11, 24.26, 24.10 Gravimetric (% of Fe): 24.35, 24.26, 24.10,24.19, 24.18, 24.32, 24.11, 24.33, 24.17, 24.12 a. Do the two methods give similar standard deviations? b. Do the two methods give similar results for the mass percent of Fe at the 95% confidence level?

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter5: Errors In Chemical Analyses

Section: Chapter Questions

Problem 5.10QAP

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A 0.9092g sample of wheat flour was analyzed by Kjeldahl method. The ammonia formed was distilled into 50.00 mL of 0.05063 M HCl; a 7.46 mL back titration with 0.04917 M NaOH was required. Calculate the % protein in the flour. Input the value only. Express in 2 SF.
A 0.1093-g sample of impure Na2CO3 was analyzed by the Volhard Method. After adding 50.00 mL of 0.06911 M AGNO3, the sample was back titrated with 0.05781 M KSCN, requiring 27.36 mL to reach the end point. Report the purity of Na2CO3 sample.
Bay Water Titration The concentration of Cl- in ocean water is about 500-600 mM. The baywater is diluted by a factor of 12.5 using a 20.00 mL volumetric pipet and a 250 mL volumetric flask. Using a 15.00 mL volumetric pipet, 15.00 mL is transferred into three clean Erlenmeyer flasks. 10 mL of 1% dextrin solution, 20 mL of de-ionized water, and 3-4 drops of indicator are added and titrated each with the AgNO3 solution. From the procedure, find: Dilution factor Volume of diluted bay water Then calculate: The [Cl-] of diluted bay water The [Cl-] of bay water Consider this information: [AgNO3] = 0.04043177 trial # Veq 1 13.91 2 13.73 3 13.9 4 13.86 5 13.87 6 13.84 average 13.85167 [Cl-]Bay = ([AgNO3](Veq(ave))/Vdil bay water pipeted) (Vflask/Vbay water)
Example You determine the acetic acid content in vinegar by titrating with a standard (known concentration) solution of NaOH to a phenolphthalein endpoint. 5.023± 0.003 g sample of vinegar is weighed. The NaOH must be standardized by KHP and 3 such titrations gave molarities of 0.1167, 0.1163 and 0.1164 M. A volume of 36.78 ± 0.03mL NaOH is used to titrate the sample. What is the percent acetic acid in the vinegar and what is the overall uncertainty?Answer: 5.12% ± 0.01%
The Kjeldahl method was used to determine the nitrogen content of a protein. A 275 µL aliquot of a 47.0 mg/mL protein solution was digested in boiling sulfuric acid. The solution was made basic and the liberated NH, was collected in 5.00 mL of 0.0512 M HCl. A volume of 7.00 mL of 0.0174 M NaOH was required to react with the excess HCl. Calculate the weight percent of nitrogen in the protein. weight percent: wt% N
Molarity of Na2S2O3 (stock solution). 0.100 M Volume of diluted bleach titrated (taken from the volumetric flask). 10ml Initial Burette Reading. 14.80 Final Burette Reading 25.60 Volume of Na2S2O3 used in the titration (mL). 10.80 Moles of Na2S2O3 used in the titration. 1.71 Moles of S2O3–2 used. 1.66 Moles of I2 initially present in titration mixture 0.83 Moles of NaOCl in the diluted bleach titrated. 0.415 Volume of bleach titrated. 1ml Mass of commercial bleaching solution titrated ?
Molarity of Na2S2O3 (stock solution). 0.100 M Volume of diluted bleach titrated (taken from the volumetric flask). 10ml Initial Burette Reading. 14.80 Final Burette Reading 25.60 Volume of Na2S2O3 used in the titration (mL). 10.80 Moles of Na2S2O3 used in the titration. 1.71 Moles of S2O3–2 used. 1.66 Moles of I2 initially present in titration mixture 0.83 Moles of NaOCl in the diluted bleach titrated. 0.415 Moles of OCl– in the diluted bleach titrated. ?
Molarity of Na2S2O3 (stock solution). 0.100 M Volume of diluted bleach titrated (taken from the volumetric flask). 10ml Initial Burette Reading. 14.80 Final Burette Reading 25.60 Volume of Na2S2O3 used in the titration (mL). 10.80 Moles of Na2S2O3 used in the titration. 1.71 Moles of S2O3–2 used. 1.66 Moles of I2 initially present in titration mixture 0.83 Moles of NaOCl in the diluted bleach titrated. 0.415 Volume of bleach titrated. 1ml Mass of NaOCl in commercial bleach titrated. ?
Molarity of Na2S2O3 (stock solution). 0.100 M Volume of diluted bleach titrated (taken from the volumetric flask). 10ml Initial Burette Reading. 14.80 Final Burette Reading 25.60 Volume of Na2S2O3 used in the titration (mL). 10.80 Moles of Na2S2O3 used in the titration. 1.71 Moles of S2O3–2 used. 1.66 Moles of I2 initially present in titration mixture 0.83 Moles of NaOCl in the diluted bleach titrated. 0.415 Mass of NaOCl in the diluted bleach titrated. ?
1. A sample of pure sodium oxalate, Na2C2O4 , weighing 0.2856 g is dissolved in water, sulfuric acid is added, and the solution titrated at 70°C , requiring 45.12 mL of a KMNO4 solution. The end point is overrun and back-titration is carried out with 1.74 mL of a 0.1032 N solution of oxalic acid. Calculate the normality of the KMNO4 solution. Hint: A redox reaction is involed between oxalate and permanganate. Look at the changes in oxidation state by determining the balanced redox reaction: 5C20,2 + + 2MN2+ 2 Mn04 + 10H* → 10CO2 + 8H20
A 0.1093-g sample of impure Na2CO3 was analyzed by the Volhard Method. After adding 50.00 mL of 0.06911 M AgNO3, the sample was back titrated with 0.05781 M KSCN, requiring 27.36 mL to reach the end point. Report the purity of Na2CO3sample.
A sample containing calcium was analyzed by gravimetry, converting all calcium to calcium oxalate monohydrate (CaC2O4 • H2O). The sample weighing 0.2654 g was dissolved by adding 6M HCl, and then ammonium oxalate solution was added to precipitate all the calcium. The precipitate was suction filtered and dried in an oven at 95 °C for one hour. The solid obtained weighed 0.3216 grams.Calculate:A) The percentage of CaCO3B) The percentage of Ca C) The percentage of CaO