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© Macmillan Learning The concentration of arsenic trioxide (As2O3) can be experimentally determined via titration with coulometrically generated iodine. To perform the analysis, solid As2O3 (MW = 197.84 g/mol) is first dissolved in an aqueous sodium bicarbonate solution, forming arsenious acid (As(OH)3) by the equilibrium shown. As2O3(s) + 3H2O(1) 2 As(OH)3(aq) The iodine is coulometrically generated by passing a constant current through the solution which contains potassium iodide (KI ). The arsenious acid in solution is then oxidized by the iodine. Once the reaction has gone to completion, excess generated iodine reacts with a starch indicator, generating a color change and signaling the titration end point. The amount of time it takes to reach the end point is used to determine the amount of As2O3 in solution. 21¯¯ = 12 + 2e¯ 12 + As(OH)3 + H2O = AsO(OH)3 + 2H+ + 21¯ An unknown amount of As2O3 was dissolved in 53.00 mL of an aqueous sodium bicarbonate solution, and to this sample, 3.0 g of KI were added. To reach the titration end point, 666 s were required at 41.8 mA. Determine the As2O3 concentration in the original sample and report the value in milligrams per milliliter (mg/mL). As2O3 concentration = mg/mL

© Macmillan Learning The concentration of arsenic trioxide (As2O3) can be experimentally determined via titration with coulometrically generated iodine. To perform the analysis, solid As2O3 (MW = 197.84 g/mol) is first dissolved in an aqueous sodium bicarbonate solution, forming arsenious acid (As(OH)3) by the equilibrium shown. As2O3(s) + 3H2O(1) 2 As(OH)3(aq) The iodine is coulometrically generated by passing a constant current through the solution which contains potassium iodide (KI ). The arsenious acid in solution is then oxidized by the iodine. Once the reaction has gone to completion, excess generated iodine reacts with a starch indicator, generating a color change and signaling the titration end point. The amount of time it takes to reach the end point is used to determine the amount of As2O3 in solution. 21¯¯ = 12 + 2e¯ 12 + As(OH)3 + H2O = AsO(OH)3 + 2H+ + 21¯ An unknown amount of As2O3 was dissolved in 53.00 mL of an aqueous sodium bicarbonate solution, and to this sample, 3.0 g of KI were added. To reach the titration end point, 666 s were required at 41.8 mA. Determine the As2O3 concentration in the original sample and report the value in milligrams per milliliter (mg/mL). As2O3 concentration = mg/mL

Introductory Chemistry: A Foundation
Introductory Chemistry: A Foundation
9th Edition
ISBN:9781337399425
Author:Steven S. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Donald J. DeCoste
Chapter17: Equilibrium
Section: Chapter Questions
Problem 66QAP: . Chromiurn(III) hydroxide dissolves in water only to the extent of 8.21105M at 25 °C. Calculate...
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© Macmillan Learning The concentration of arsenic trioxide (As2O3) can be experimentally determined via titration with coulometrically generated iodine. To perform the analysis, solid As2O3 (MW = 197.84 g/mol) is first dissolved in an aqueous sodium bicarbonate solution, forming arsenious acid (As(OH)3) by the equilibrium shown. As2O3(s) + 3H2O(1) 2 As(OH)3(aq) The iodine is coulometrically generated by passing a constant current through the solution which contains potassium iodide (KI ). The arsenious acid in solution is then oxidized by the iodine. Once the reaction has gone to completion, excess generated iodine reacts with a starch indicator, generating a color change and signaling the titration end point. The amount of time it takes to reach the end point is used to determine the amount of As2O3 in solution. 21¯¯ = 12 + 2e¯ 12 + As(OH)3 + H2O = AsO(OH)3 + 2H+ + 21¯ An unknown amount of As2O3 was dissolved in 53.00 mL of an aqueous sodium bicarbonate solution, and to this sample, 3.0 g of KI were added. To reach the titration end point, 666 s were required at 41.8 mA. Determine the As2O3 concentration in the original sample and report the value in milligrams per milliliter (mg/mL). As2O3 concentration = mg/mL
Transcribed Image Text:© Macmillan Learning The concentration of arsenic trioxide (As2O3) can be experimentally determined via titration with coulometrically generated iodine. To perform the analysis, solid As2O3 (MW = 197.84 g/mol) is first dissolved in an aqueous sodium bicarbonate solution, forming arsenious acid (As(OH)3) by the equilibrium shown. As2O3(s) + 3H2O(1) 2 As(OH)3(aq) The iodine is coulometrically generated by passing a constant current through the solution which contains potassium iodide (KI ). The arsenious acid in solution is then oxidized by the iodine. Once the reaction has gone to completion, excess generated iodine reacts with a starch indicator, generating a color change and signaling the titration end point. The amount of time it takes to reach the end point is used to determine the amount of As2O3 in solution. 21¯¯ = 12 + 2e¯ 12 + As(OH)3 + H2O = AsO(OH)3 + 2H+ + 21¯ An unknown amount of As2O3 was dissolved in 53.00 mL of an aqueous sodium bicarbonate solution, and to this sample, 3.0 g of KI were added. To reach the titration end point, 666 s were required at 41.8 mA. Determine the As2O3 concentration in the original sample and report the value in milligrams per milliliter (mg/mL). As2O3 concentration = mg/mL
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