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Chapter 16: Q25P (page 392)

The pathogenic bacterium Salmonella enterica uses tetrathionate found in the human gut as an oxidant- just as we useO2to metabolize our food. Write the half-reaction in which tetrathionate serves as an oxidant. Is tetrathionate as powerful an oxidant asO2?

Short Answer

Expert verified

The half reaction of tetrathionate as an oxidant is,

S4O62-+2e⇇2S2O32

Step by step solution

01

Definition of redox titration

  • Redox reactions are oxidation-reduction chemical reactions in which the oxidation states of the reactants change. The term redox refers to the reduction-oxidation process.
  • In a redox reaction, or Oxidation-Reduction process, the oxidation and reduction reactions always happen at the same time.
02

Determine the half reaction in which tetrathionate as an oxidant.

Half reaction of tetrathionate as an oxidant:

S4O62-+2e⇇2S2O32E0=0.080V

Half reaction of oxygen as an oxidant:

12O2+2H+2e-⇇H2OE0=1.23V

Values of standard reduction potential for each reaction can be found in appendix H. Since oxygen has a higher potential value it is a stronger oxidant than tetrathionate.

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Most popular questions from this chapter

Some people have an allergic reaction to the food preservative sulfite (SO32-), which can be measured by instrumental methods 37 or by a redox titration: To 50.0mL of wine were added 50.0mL of solution containing (0.8043gKIO3+6.0gKI)/100mL . Acidification with 1.0 mL of 6.0MH2SO4 quantitatively converted role="math" localid="1663606948648" lO3 into l3 . The l3 reacted with SO32- to generate role="math" localid="1663607055826" SO42- , leaving excess l3 in solution. The excess l3 required of 12.86mLof0.04818MNa2S2O3to reach a starch end point.

(a) Write the reaction that occurs when H2SO4is added to KIO3+ KI and explain why 6.0 gKI were added to the stock solution. Is it necessary to measure out 6.0 g accurately? Is it necessary to measure 1.0 mL
ofH2SO4 accurately?

(b) Write a balanced reaction betweenl3 and sulfite.

(c) Find the concentration of sulfite in the wine. Express your answer in mol/L and inmgSO32- per liter.

(d) t test. Another wine was found to contain 277.7mgSO32-/Lwith a standard deviation of ±2.2mg/Lfor three determinations by the iodimetric method. A spectrophotometric method gaverole="math" localid="1663607422230" 273.2±2.1mg/L in three determinations. Are these results significantly different at the 95 % confidence level?

Whenof unknown were passed through a Jones reductor, molybdate ion (MoO42-)was converted into Mo3+. The filtrate required 16.43mLof 0.01033MKMnO4to reach the purple end point.

MnO4-+Mo3+→Mn2++MoO22+

A blank required 0.04mL. Balance the reaction and find the molarity of Molybdate in the unknown.

Explain what we mean by pre-oxidation and pre-reduction. Why is it important to be able to destroy the reagents used for these purposes?

A 25.00mL volume of commercial hydrogen peroxide solution was diluted to 250.0mL in a volumetric flask. Then 250.0 of the diluted solution were mixed with 200mL of water and 20mLof 3MH2SO4 and titrated with 0.02123MKMnO4. The first pink color was observed with 27.66mL of titrant. A blank prepared from water in place ofH2O2 required 0.04Ml to give visible pink color. Using theH2O2 reaction in Table16 - 3, find the molarity of the commercial H2O2.

Iodometric analysis of high-temperature superconductor. The procedure in Box16 - 3 was carried out to find the effective copper oxidation state, and therefore the number of oxygen atoms, in the formula YBa2Cu3O7, where 0≤z≤0.5.

(a) In Experiment A of Box 16 - 3, 1.00 g of superconductor required 4.55 mmol of role="math" localid="1654948290716" S2O32-. In Experiment B,1.00 g of superconductor required 5.68 mmol ofS2O32- Calculate the value of z in the formula YBa2Cu3O7-z(FM ).

(b) Propagation of uncertainty. In several replications of Experiment A, the thiosulfate required was 4.55(±0.010)mmol of role="math" localid="1654948278531" S2O32- per gram of YBa2Cu3O7. In ExperimentB, the thiosulfate required was 5.68(±0.05)mmol of S2O32-per gram. Calculate the uncertainty x of in the formulaYBa2Cu3Ox.
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