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प्रश्न
Why is the `"E"_(("V"^(3+)//"V"^(2+)))^"o"` value for vanadium comparatively low?
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उत्तर
The low value for V is related to the stability of V2+ (half-filled t2g level).
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संबंधित प्रश्न
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
Give reasons: Sc3+ is colourless in aqueous solution whereas Ti3+ is coloured.
Which among the following transition metal has the lowest melting point?
Read the passage given below and answer the following question:
The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.
In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.
Assertion: Transition metals form protective oxide films.
Reason: Oxides of transition metals are always stoichiometric.
When acidified \[\ce{K2Cr2O7}\] solution is added to \[\ce{Sn^{2+}}\] salts then \[\ce{Sn^{2+}}\] changes to ______.
Highest oxidation state of manganese in fluoride is \[\ce{+4 (MnF4)}\] but highest oxidation state in oxides is \[\ce{+7 (Mn2O7)}\] because ______.
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
A complex in which dsp2 hybridisation takes place is ______.
Give reasons for the following statement:
Transition metals and most of their compounds show paramagnetic behaviour.
Assertion (A): Transition metals have high enthalpy of atomisation.
Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.
