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The d-And-f-Block Elements

Long Answer Type

281. What is the cause of lanthanide contraction?

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Short Answer Type

282. What happens when acidified potassium dichromate solution is added to potassium iodide solution?

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283.

Which out of V(IV) and V(V) is paramagnetic and why?

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284.

Why does a transition series contain only ten elements?

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285.

Why are Cd²⁺salts white?

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286.

Which one of the two Co or Zn would be repelled by a magnetic field?

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287.

Why is electronic configuration 1s²2s²2p⁶3s²3p⁶4s²3d⁴ not correct for ground state of Cr (24)?

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288.

How is the magnetic moment of a species related to number of unpaired electrons?

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289.

Which property of the transition metals makes them good catalyst?

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290.
What is the effect of increasing pH on K₂Cr₂O₇ solution?

The potassium dichromate (K₂Cr₂O₇), solution contain dichromate (Cr₂O₇^2- ion . The ion is less basic and so increase in P_H increase in the basicity of the compound.

In simple words, by decreasing hydrogen ion concentration the dichromate ion is converted to chromate ion or vice versa.

Cr₂O₇^2- +2OH^- à 2CrO₄^2- +H₂O

2CrO₄^2- +2H⁺ à Cr₂O₇^2-+H₂O

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