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NEET-XII-Chemistry

08: The d-and f-Block Elements

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Qstn# II-17-i Prvs-QstnNext-Qstn
  • #17-i
    The stability of Fe3+ in acid solution as compared to that of Cr3+ or Mn3+ and
    () The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
    Ans : The value for Fe3+/Fe2+ ­­ is higher than that for Cr3+/Cr2+ and lower than that for Mn3+/Mn2+. So, the reduction of Fe3+ to Fe2+ is easier than the reduction of Mn3+ to Mn2+, but not as easy as the reduction of Cr3+ to Cr2+. Hence, Fe3+ is more stable than Mn3+, but less stable than Cr3+. These metal ions can be arranged in the increasing order of their stability as: Mn3+ < Fe3+ < Cr3+
    () The reduction potentials for the given pairs increase in the following order.

    Mn2+ / Mn < Cr2+ / Cr < Fe2+ /Fe

    So, the oxidation of Fe to Fe2+ is not as easy as the oxidation of Cr to Cr2+ and the oxidation of Mn to Mn2+. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: Fe < Cr < Mn
  • #17-ii
    The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.
    Ans : The reduction potentials for the given pairs increase in the following order.

    Mn2+ / Mn < Cr2+ / Cr < Fe2+ /Fe

    So, the oxidation of Fe to Fe2+ is not as easy as the oxidation of Cr to Cr2+ and the oxidation of Mn to Mn2+. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: Fe < Cr < Mn