I need a full answer and correct for self-test 5.3 EXAMPLE 5.3 Using the electro

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I need a full answer and correct for self-test 5.3

EXAMPLE 5.3 Using the electrochemical series Among the couples in Table 5.2 is the permanganate ion, Mno,, the common analytical reagent used in redox titrations of iron. Which of the ions Fe, CI, and Ce" can permanganate oxidize in acidic solution? Answer We need to note that a reagent that is capable of reducing Mno, ions must be the reduced form of a redox couple having a more negative standard potential than the couple Mno;/Mn. The standard potential of the couple MnO;/Mn2+ in acidic solution is +1.51 V. The standard potentials of Fe Fe", cl,/CI, and Ce Ce" are +0.77 +1.36, and +1.76 V, respectively It follows that l MnO; ions are suffciently strong oxidizing agents in acidic solution (pH 0) to oxidize Fe and C which have less positive standard potentials. Permanganate ions cannot oxidize Ce, which has a more positive standard potential. It should be noted that the presence of other ions in the solution can modify the potentials and the conclusions (Section 5.10); this variation with conditions is particularly important in the case of H ions, and the influence of pH is discussed in Section 5.6. The ability of Mn0, ions to oxidize Cl means that HCl cannot be used to acidify redox reactions involving permanganate but H, S0, is used instead. Self test 5.3 Another common analytical oxidizing agent is an acidic solution of dichromate ions, Cr,0. for which E (Cr,0, C)138 V. Is the solution useful for a redox titration of Fe' to Fe2 Could there be a side reaction when Cl is present?

Explanation / Answer

A reagent that is capable of reducing Cr2O72- ions must be the reduced form of a redox couple having a more negative standard potential than the couple Cr2O72-/Cr3+ .The standard potential of Fe3+/Fe2+ is +0.77V and standard ppotential of Cl2/Cl- is +1.36 V.The standard potential of  Cr2O72-/Cr3+ is +1.38V .So Cr2O72- ions are sufficiently strong oxidizing agent to oxidize Cl- and Fe2+ which have less positive standard potential.so yhe solution is useful for a redox totration of Fe2+ to Fe3+ .obviously there will be a side reaction if Cl- is present as Cl- will also oxidise to Cl2

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