A 5.27-g sample of an ant-control preparation was decomposed by wet ashing with H₂SO4 and HNO3. The arsenic in une residue was reduced to the trivalent state with hydrazine. After the excess reducing agent had been removed, the arsenic(III) was oxidized with electrolytically generated 12 in a faintly alkaline medium: HASO + 1₂ + 2HCO HASO + 2 + 2CO + H₂O The titration was complete after a constant current of 105.2 mA had been passed for 10 min and 43 s. Express the results of this analysis in terms of the percentage As2O3 in the original sample.

A 5.27-g sample of an ant-control preparation was decomposed by wet ashing with H₂SO4 and HNO3. The arsenic in une residue was reduced to the trivalent state with hydrazine. After the excess reducing agent had been removed, the arsenic(III) was oxidized with electrolytically generated 12 in a faintly alkaline medium: HASO + 1₂ + 2HCO HASO + 2 + 2CO + H₂O The titration was complete after a constant current of 105.2 mA had been passed for 10 min and 43 s. Express the results of this analysis in terms of the percentage As2O3 in the original 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

Chapter23: Potentiometry

Section: Chapter Questions

Problem 23.23QAP: The following cell was found to have a potential of —0.492 V: Ag|AgCl(sat’d)||HA(0.200 M),NaA(0.300...

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Why must the charge balance in oxidation-reduction reactions?
The following cell was found to have a potential of —0.492 V: Ag|AgCl(sat’d)||HA(0.200 M),NaA(0.300 M)|H2(1.00 atm),Pt Calculate the dissociation constant of HA, neglecting the junction potential.
For the following half-reaction, = 2.07 V: A1F63(aq)+3eAl(s)+6F(aq) Using data from Table 17-1, calculate the equilibrium constant at 25C for the reaction A13+(aq)+6F(aq)A1F63(aq)K=?
Explain why colour of KMnO4 disappears when oxalic acid is added to its solution in acidic medium.
A 100.0-mL sample of spring water was treated to convert any iron present to Fe21. Addition of25.00-mL of 0.002517 M K2Cr2O7 resulted in the reaction6Fe2+ + Cr2O7 2- + 14H+ → 6Fe3+ + 2Cr3+ + 7H2OThe excess K2Cr2O7 was back-titrated with 8.53 mL of 0.00949 M Fe2+ solution. Calculate the concentration of iron in the sample in parts per million.
Given the unbalanced reaction Cu2O3 + Cl- ⇌ Cu2+ + HClO2, which takes place in acidic solution, what is thecoefficient of water in the balanced reaction equation?
5. 0.1500 g sample of chromium ore was dissolved and the chromium oxidized to chromate ion. The solution was treated with 25.00 mL of 0.3500 M AGNO3. The resulting precipitate, from the reaction of the excess and analyte in 1: 1 mole relationship, Ag2CrO4 was removed and discarded. The excess AGNO3 required 30.50 mL of 0.200 M KSCN for titration in a 1:1 mole relationship. Calculate the % Cr2O3 in the ore if the mole relationship between Cr2O3 and CrO42- is 1:2 respectively.
3. A 100.0 mL sample of ground water was treated to convert the iron present to Fe2+. Addition of 25.00 mL of 0.002412 M K2Cr2O7 resulted in the reaction below. 6Fe2+ + Cr2O72 - + 14H+ → 6Fe3+ + 2Cr3+ + 7H2O The excess K2Cr2O7 was back-titrated with 8.12 mL of 0.00859 M Fe2+ solution. What is the concentration of Fe in the sample in parts per million?
7) Write Electrochemical equations for the oxidation and reduction processes which occur during: i. The corrosion of aluminium by air-free sulfuric acid ii. Corrosion of iron in aerated sulfuric acid containing ferric sulphate iii. Corrosion of copper in aerated sulfuric acid containing ferric sulphate iv. Corrosion of nickel in seawater v. Corrosion of iron in air-free ferric chloride solution vi. The uniform corrosion of a 50% iron-chromium alloy in aerated hydrochloric acid
46 Solution of hydrogen sulfite was added to a solution of potassium dichromate. H2SO3 + Cr2072- Cr3+ + SO42- pr the reaction above: Relate the observations to the species involved Write balanced half equations and the overall equation for the reaction Identify with reasons the oxidant and the reductant in terms of change in oxidation number or electron transfer.
A dilute solution of CuSO4 was electrolyzed using Pt- electrodes. The amount of Cu in the anodic solution was found to be 0.6350 g and 0.6236 g before and after electrolysis, respectively. The weight of Ag deposited in a silver coulometer, placed in series, was found to be 0.1351 g. Calculate the transport numbers of Cu+2 and SO4-2.
Give the half reaction of the reduction of Cr2O7-2 in chromic acid and the reduction of ClO-1 in the hypochlorite oxidation.