A 0.400-g sample of toothpaste was boiled with a 50-mL solution containing a citrate buffer and NaCl to extract the fluoride ion. After cooling, the solution was diluted to exactly 100 mL. The potential of a selective ion/calomel system in a 25.0-mL aliquot of the sample was found to be - 0.1823 V. Addition of 5.0 mL of a solution containing 0.00107 mg F-/mL caused the potential to change to 0.2446 V. Calculate the weight percent F- in the sample.

A 0.400-g sample of toothpaste was boiled with a 50-mL solution containing a citrate buffer and NaCl to extract the fluoride ion. After cooling, the solution was diluted to exactly 100 mL. The potential of a selective ion/calomel system in a 25.0-mL aliquot of the sample was found to be - 0.1823 V. Addition of 5.0 mL of a solution containing 0.00107 mg F-/mL caused the potential to change to 0.2446 V. Calculate the weight percent F- in the sample.

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter15: Molecular Luminescence Spectrometry

Section: Chapter Questions

Problem 15.10QAP

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A 0.3045 g of CaCO3 primary standard was dissolved using concentrated HCl, evaporated to incipient dryness and quantitatively transferred to a 250 mL volumetric flask, and diluted to mark. A 10 mL of aliquot was then transferred to an Erlenmeyer flask, together with 5mL buffer and 5 drops of EBT indicator, and was used to standardize the EDTA titrant. The solution turned blue after the addition of 24.10 mL of EDTA. A blank correction was performed and was determined to be 0.4 mL. What is the concentration of EDTA obtained (MW CaCO3 = 100.0869 g/mol)?
A sample of anhydrous Na2CO3 (FM = 105.989) is suspected to be contaminated with eitherNaHCO3 (FM = 84.007) or NaOH (FM = 39.997) To verify the suspicion, a 0.7483 g sample was dissolved to prepare a 50.00 mL solution, and a 10.00 mL aliquot was taken to prepare a 100 mL solution, where 25.00 mL was analyzed using single flask method. If the sample requires 27.50 mL of standard 0.0125 N HCl to reach the phenolphthalein endpoint and another 28.40 mL to reach the bromcresol green endpoint, calculate the percentagecomposition (in %w/w) of all the basic components in the sample.
A 0.3045 g of CaCO3 primary standard was dissolved using concentrated HCl, evaporated to incipient dryness, and quantitatively transferred to a 250 mL volumetric flask and diluted to mark. A 10 mL of aliquot was then transferred to an Erlenmeyer flask, together with 5mL buffer and 5 drops of EBT indicator, and was used to standardize the EDTA titrant. The solution turned blue after the addition of 24.10 mL of EDTA. A blank correction was made and was determined to be 0.4 mL. [Analysis] A 30 mL unknown water sample was treated with 37.6 mL of EDTA. A blank correction was made and was determined to be 0.4 mL. What is the concentration of Ca2+ (40.0780 g/mol) in ppm?
For Indirect Iodometric Analysis of Copper... ~0.0896g KIO3 necessary to consume 350mL of 0.1 M Na2S2O3, Na2S2O3 is stored in an amber glass bottle until ready for use. Primary Standard KIO3 has 2g of KI, 50mL of DI water, and 10 mL of 1.0M HCl is added then immediately titrated with Na2S2O3 until medium yellow or straw... then 5mL of starch indicator is added and titrated again until blue black color turns clear. Unknown CuO use 1.2G of Unknown, 20mL of HNO3 heated until sample dissolved, 25 mL of DI water added and boiled until clear light blue color, after cooling 1:1 NH3 added (~34.47 mL of NH4OH reagent) until permanent deep blue color amine complex, 2g of NH4HF2 added and swirled until dissolved, 3 g of KI is added then titrated immediately with Na2S2O3 until brown color of iodide is nearly gone (brown milk color), 2 g of KSCN and 3 mL of starch indicator is then added with titration continuing until disappearance of new blue black color. 1. Na2CO3 is often added to thiosulfate…
For Indirect Iodometric Analysis of Copper... ~0.0896g KIO3 necessary to consume 350mL of 0.1 M Na2S2O3, Na2S2O3 is stored in an amber glass bottle until ready for use. Primary Standard KIO3 has 2g of KI, 50mL of DI water, and 10 mL of 1.0M HCl is added then immediately titrated with Na2S2O3 until medium yellow or straw... then 5mL of starch indicator is added and titrated again until blue black color turns clear. Unknown CuO use 1.2G of Unknown, 20mL of HNO3 heated until sample dissolved, 25 mL of DI water added and boiled until clear light blue color, after cooling 1:1 NH3 added (~34.47 mL of NH4OH reagent) until permanent deep blue color amine complex, 2g of NH4HF2 added and swirled until dissolved, 3 g of KI is added then titrated immediately with Na2S2O3 until brown color of iodide is nearly gone (brown milk color), 2 g of KSCN and 3 mL of starch indicator is then added with titration continuing until disappearance of new blue black color. 4. Why is the starch indicator solution…
A foot powder sample containing Zn was dissolved on 50.00 mL water and was titrated to the end point color with 22.57 mL of 0.01639 M EDTA at pH=4. (α= 3.61x109, KKzny2 = 3.2 x 1016). The pZn in the sample is:
A 10 ml of ascorbic acid (MW=176.1) injection was transferred to a 100 ml volumetric flask and made up to volume with deionized water. A 20 ml of the diluted injection was transferred to a conical flask and titrated with Iodine VS using starch mucilage as the indicator. The iodine solution was standardized against a solution of sodium thiosulfate primary standard (MW=248.2). Results: Weight of sodium thiosulfate used to prepare 100 mL primary standard solution = 2.501 g Volume of thiosulfate solution required to titrate 25 mL of Iodine solution = 24.83 mL Volume of iodine solution required to titrate 20 mL of the diluted ascorbic acid injection = 21.55 mL Stated content of the injection = 10% w/v Calculate the % of the stated content in the injection. (Round-off your answer to 2-decimal places) Answer = ____%
A 10 ml of ascorbic acid (MW=176.1) injection was transferred to a 100 ml volumetric flask and made up to volume with deionized water. A 20 ml of the diluted injection was transferred to a conical flask and titrated with Iodine VS using starch mucilage as the indicator. The iodine solution was standardized against a solution of sodium thiosulfate primary standard (MW=248.2). Results: Weight of sodium thiosulfate used to prepare 100 mL primary standard solution = 2.501 g Volume of thiosulfate solution required to titrate 25 mL of Iodine solution = 24.83 mL Volume of iodine solution required to titrate 20 mL of the diluted ascorbic acid injection = 21.55 mL Stated content of the injection = 10% w/v Calculate the % of the stated content in the injection.
A 1.00 mL aliquot of stock Na2S2O3 solution (0.0675 M) was diluted to 100. 0 mL. This was used to titrate a 50.00 mL water sample for Winkler Determination of D.O. The sample required 8.55 mL of the titrant. Compute for the ppm O2 (molar mass of O2 = 32.00).
A 30.00-L air sample was passed through an absorption tower containing a solution of Cd+2, where H2S was retained as CdS. The mixture was acidified and treated with 10.00 mL of 0.01070 M I2. After the reaction: S-2 + I2 S(s) + 2 I- was complete, the excess iodine was titrated with 12.85 mL of 0.01344 M thiosulfate. Calculate the concentration of H2S in ppm (w/w); use 1.20 g/L for the density of the gas stream. Molar Mass: H2S = 34.082
A sample of anhydrous Na2CO3 (FM = 105.989) is suspected to be contaminated with either NaHCO3 (FM = 84.007) or NaOH (FM = 39.997) To verify the suspicion, a 0.7483 g sample was dissolved to prepare a 50.00 mL solution, and a 10.00 mL aliquot was taken to prepare a 100 mL solution, where 25.00 mL was analyzed using single flask method. If the sample requires 27.50 mL of standard 0.0125 N HCl to reach the phenolphthalein endpoint and another 28.40 mL to reach the bromcresol green endpoint, calculate the percentage composition (in %w/w) of all the basic components in the sample.
a. What mass of Ag2SO4 is formed when 34 mL of 0.300 M AgNO3 are mixed with 26 mL of 30.0 g/L Na2SO4? b. Potassium can be determined by flame emission spectrometry (flame photometry) using lithium internal standard. The following data were obtained for standard solutions of KCI and an unknown containing a constant, known amount of Lil as the internal standard. The intensity of a blank was 0.04. Calculate the concentration of K in the unknown. ck, ppm Intensity of K emission Intensity of Li emission 5.0 34.7 5.8 20.0 110.2 9.1 Unknown 57.3 6.8