The d-And-f-Block Elements

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Why is cerium a good analytical reagent?

Cerium (Ce) shows +4 oxidation state as in this it acquires stable noble gas configuration but it is a strong oxidising agent and oxidises to Ce3+ (common) state. Its E° value for Ce4+/Ce3+ is 1.74 V. It oxidises water but the rate of reaction is slow and thus can be studied in detailed and analysed. Hence Ce acquires great use in analytical reagents.
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    Complete the following reaction equations:
    (i) Cr2O7 2 + Sn2+ + H+ →
    (ii) MnO4– + Fe2+ + H+ →

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    Give reasons:
    Ce4+ is used as an oxidising agent in volumetric analysis.

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    Actinide cations are coloured? Why?

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    Why La, Gd and Lu has low value of 3rd ionisation enthalpies?

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    Give reasons:
    Zn2+ salts are white while Cu2+ salts are blue.

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    Given below are the electrode potential values, E° for some of the first row of transition elements:
    Elements V(23) Cr(24) Mn(25)Fe(26)Co(27)Ni(28) Cu(29)
    E°M2+/M(V) –1.18 – 0.91 – 0.44 – 0.28 –0.28 –0.25 +0.34
    Explain the irregularities in these values on the basis of electronic structures of atoms.
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    Give reasons:
    Among transition metals, the highest oxidation state is exhibited in oxoanions of a metal.

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    Explain the following facts:
    Transition metals form coloured complexes.

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    Eu2+, Yb2+ are good reductants whereas Tb+4 is an oxidant. Why?
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