A 2.067 g of macrogol monostearate (average molecular weight 706. 5) was added to a 200 ml flask and 25 ml of an ethanolic solution of potassium hydroxide (molecular weight 56.11, ca 0.5 M) was added. The sample was heated under a reflux condenser for 1 hour. The excess of alkali was then titrated with 0.5126 M hydrochloric acid using phenolphthalein solution as an indicator. The operation was repeated without the macrogol monostearate. Results Volume of HCI required to titrate the excess alkali = 18.35 ml Volume of HCI required to titrate the blank = 24.03 ml Calculate the saponification value for the macrogol stearate. Answer: _____ mg/g

A 2.067 g of macrogol monostearate (average molecular weight 706. 5) was added to a 200 ml flask and 25 ml of an ethanolic solution of potassium hydroxide (molecular weight 56.11, ca 0.5 M) was added. The sample was heated under a reflux condenser for 1 hour. The excess of alkali was then titrated with 0.5126 M hydrochloric acid using phenolphthalein solution as an indicator. The operation was repeated without the macrogol monostearate. Results Volume of HCI required to titrate the excess alkali = 18.35 ml Volume of HCI required to titrate the blank = 24.03 ml Calculate the saponification value for the macrogol stearate. Answer: _____ mg/g

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter13: Titrations In Analytical Chemistry

Section: Chapter Questions

Problem 13.5QAP

See similar textbooks

Similar questions

The ethyl acetate concentration in an alcoholic solution was determined by diluting a 10.00-mL sample to 100.00 mL. A 20.00-mL portion of the diluted solution was refluxed with 40.00 mL of 0.04672 M KOH. After cooling, the excess OH2 was back-titrated with 3.41 mL of 0.05042 M H2SO4. Calculate the amount of ethyl acetate (88.11 g/mol) in the original sample in grams.
A student measured 20 drops of vinegar and one drop of phenolphthalein solution into a well of her well plate. After she had added 35 drops of NaOH solution to the same well, the well was full, but she had still not reached the titration endpoint. She then took a clean pipet and transferred some of the titration mixture into a second well. She rinsed the pipet with a few drops of distilled water and transferred the rinse water into the titration mixture in the second well. Then she continued adding NaOH solution to both wells until she reached the endpoint in both wells. She then recorded the total number of drops of NaOH solution added to both wells and used it to calculate the data for her vinegar titration. Briefly comment on her procedure and the accuracy of her results.
A two-liter sample of mineral water was evaporated to a small volume, following which the potassium ion was precipitated with excess sodium tetraphenylboron: K+ NaB(C,Hs)4 → KB(CHs)4 ) The precipitate was filtered, washed and redissolved in acetone. The analysis was completed by a Mohr titration that required 43.85-mL of 0.03941M AGNO3: KB(C,Hs)4 19 + Ag → AgB(CHs)« co) + K** Calculate the potassium ion concentration (parts per million) of the water sample. Molar Mass: K = 39.10
An impure sample of oxalis acid was oxidized by potassium permanganate. A 0.261g sample of oxalis acid was dissolved and the solution was diluted to 100ml. A 25.0 ml portion of the oxalis acid solution was titrated with 26.2ml of 0.0107M potassium permanganate. How many moles of oxalis acid were titrated and what is the percent purity of the oxalis acid sample?
A 1.000 liter sample of sea water was evaporated to a small volume and treated with an excess of sodium tetraphenylboron. The precipitated tetraphenylboron was filtered and then redissolved in acetone. The analysis was completed by a Mohr titration that required 34.32 ml of 0.03875 M AGNO3. Calculate the parts per million of potassium in the sea water sample. K* + NaB(C,Hs)4 → KB(C,Hs)4(s) + Na* ; Ag* + KB(C,H5)4 > AgB(CgHs)4(6) + K*
A 50-mL solution of 0.5005 N standard NaOH was added to a 0.9250-g sample of Aspirin and was boiled for 10 minutes. After cooling a full pipet of phenolphthalein was added to the solution before it was titrated with 24.7 mL of 0.5015 N standard HCl solution until the disappearance of the pink color. The same procedure was carried using a blank which consumed 4.6 mL of the same standard acid. Calculate for the %Aspirin in the sample. Atom weights: C =12, H =1, O =16.
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
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. ?
A 2.00 mL sample of serum is analyzed for protein by the modified Kjeldahl method. The sample is digested and the resulting ammonia is distilled into a boric acid solution, consuming 15.0 mL of standard HCl to titrate the ammonium borate. HCl is standardized by treating 0.330 g of pure (NH₄)₂SO₄ in the same way. If 33.3 mL of acid is consumed in the standardization titration, what is the serum protein concentration in g% (wt/vol)?
A mass of 3.3214 g of sodium bicarbonate was dissolved and diluted to 250.00 ml of aqueous solution. A 29.550X mL of sodium bicarbonate solution was used to neutralise 25.00 ml of H2SO, solution during a titration. Calculate the molar concentration of H2SO4 solution.