Principles of Instrumental Analysis
7th Edition
ISBN: 9781305577213
Author: Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher: Cengage Learning
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Chapter 24, Problem 24.9QAP
Interpretation Introduction
Interpretation:
The percentage of
Concept introduction:
The Faraday’s law states that the quantity of electric change and mass of the substance is directly proportional to the amount of that substance liberated or deposited in the process of
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The digestion of a 0.1432 g sample of a compound containing phosphorous in a mixture of HNO3
and H2SO, resulted in the formation of CO2, H2O and H3PO4 Addition of ammonium molybdate
yielded a solid having the composition (NH)3PO, 12M0O3 (MW=1876.3 g/mol). This precipitate
was filtered washed, and dissolved in 50 00 mL of 0.2000 M NaOH:
(NH,)3PO4-12MO03(s)+ 26OH (aq)
HPO,2 (aq) +12M00,2 (aq) +14H2O(1) + 3NH3(g)
After the solution was boiled to remove NH3, the excess NaOH was titrated with 14.71mL of 0.1741
M HCI to a phenolphthalein end point (back titration). Calculate the percentage of phosphorous
in the solid sample.
6.19%
10.6%
O 27.6%
O0 238%
O 19.5
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 + 2HCO3 → HASO +21+ 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.
Consider the reaction between dissolved Fe2+ and elemental sulfur (S0) to form hematite (Fe2O3) and sulfide a) Identify the oxidant and reductant in this reaction, determine half-reactions, and balance thereaction.
b) Is this reaction thermodynamically favorable?
c) Would you expect HS- to react readily with Fe2O3 (i.e. the reverse of the reaction)?
Chapter 24 Solutions
Principles of Instrumental Analysis
Ch. 24 - Prob. 24.1QAPCh. 24 - Calculate the minimum difference in standard...Ch. 24 - Prob. 24.3QAPCh. 24 - Halide ions can he deposited at a silver anode,...Ch. 24 - What cathode potential (versus SCE) would be...Ch. 24 - Calculate the Lime required for a constant current...Ch. 24 - Calculate the time required for a constant current...Ch. 24 - Prob. 24.8QAPCh. 24 - Prob. 24.9QAPCh. 24 - A 0.0712-g sample of a purified organic acid was...
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- Explain why colour of KMnO4 disappears when oxalic acid is added to its solution in acidic medium.arrow_forwardGive the half reaction of the reduction of Cr2O7-2 in chromic acid and the reduction of ClO-1 in the hypochlorite oxidation.arrow_forward(a) What is the percentage of MnO2 in a pyrolusite ore if a sample weighing 0.4000 g is treated with a 0.6000 g of pure H2C2O4.2H20 and dilute H2SO4 and after reduction has taken place (MnO2 + H2C2O4 + 2H+ Mn2+ + 2CO2 + 2H2O), the excess oxalic acid requires 26.26 mL of 0.1000 N KMNO4 for titration? (b) If pure As2O3 were used instead of oxalic acid, how many grams would be required in order for the other numerical data to remain the same?arrow_forward
- (a) What is the percentage of MnO2 in a pyrolusite ore if a sample weighing 0.4000g is treated with 0.6000g of pure H2C2O4•2H2O and dilute H2SO4 and after reduction has taken place (MnO2 + H2C2O4 + 2H+→ Mn2++ 2CO2 + 2H2O), the excess oxalic acid requires 26.26ml of 0.1000N KMnO4 for titration? (b) If pure As2O3 were used instead of oxalic acid, how many grams would be required in order for the other numerical data to remain the same?arrow_forwardThe Ksp at 298 K for iron(II) fluoride is 2.4 * 10-6. (a) Write a half-reaction that gives the likely products of the two-electron reduction of FeF21s2 in water.arrow_forward46 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.arrow_forward
- Write a balanced net-ionic equations to describe a. reduction of Fe3+ to fe2+ by SO2b. reaction of H2MoO4 in a Jones reductorc. oxidation of HNO2 by a solution of MnO4-d. reaction of aniline (C6H4NH2) with a mixture of KBrO3 and KBr in acidic solutione. air oxidation of HAsO3(2-) to HAsO4(2-)f. reaction of KI with HNO2 in acidic solutionarrow_forward(b) Draw and explain the cyclic voltammo- gram of Fe (n-C5H5)2 in CH₂Cl2, where [NBu4] [PF6] is used as supporting electrolyte and Pt electrode as working electrode.arrow_forwardWrite balanced net-ionic equations to describe: (a) the reduction of Fe3+ to Fe2+ by SO2 (b) the reaction of H2MoO4 in a Jones reductor (c) the oxidation of HNO2 by a solution of MnO-4. (d) The reaction of aniline (C6H4NH2) with a mixture of KBrO3 and KBr in acidic solution (e) the air oxidation of HAsO2-3 to HasO2-4 (f) the reaction of KI with HNO2 in acidic solution Please answer letters d, e, and farrow_forward
- 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.arrow_forwardA 7.13 g sample of an ant-control preparation was decomposed by wet-ashing with H₂SO and HNO₂. The As in the residue was reduced to the trivalent state with hydrazine. After removal of the excess reducing agent, the As(III) required 31.46 mL titration with 0.03142 M I₂ in a faintly alkaline medium. What is the % As in the original sample? Select one: O 1.20% 2.08% O 1.04% O 00 0.519%arrow_forwardWhen I was a boy, I watched Uncle Wilbur measure the iron content of runoff from his banana ranch. He acidified a 25.0-mL sample with HNO3 and treated it with excess KSCN to form a red complex. (KSCN itself is colorless.) He then diluted the solution to 100.0 mL and put it in a variablepathlength cell. For comparison, he treated a 10.0-mL reference sample of 6.80 3 1024 M Fe31 with HNO3 and KSCN and diluted it to 50.0 mL. The reference was placed in a cell with a 1.00-cm pathlength. Runoff had the same absorbance as the reference when the pathlength of the runoff cell was 2.48 cm. What was the concentration of iron in Uncle Wilbur’s runoff ?arrow_forward
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