Account for the following :E° value for the Mn3+/Mn2+ couple is

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 Multiple Choice QuestionsShort Answer Type

351.

Explain giving reasons:

(i) Transition metals and their compounds generally exhibit a paramagnetic behaviour.

(ii) The chemistry of actinoids is not as smooth as that of lanthanoids.
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352.

Complete the following chemical equations:

straight i right parenthesis space MnO subscript 4 superscript minus straight space left parenthesis aq right parenthesis straight space plus straight space straight S subscript 2 straight O subscript 3 superscript 2 minus end superscript straight space left parenthesis aq right parenthesis straight space plus straight space straight H subscript 2 straight O straight space left parenthesis straight l right parenthesis straight space rightwards arrow
ii right parenthesis space Cr subscript 2 straight O subscript 7 superscript 2 minus end superscript straight space left parenthesis aq right parenthesis straight space plus straight space Fe to the power of 2 plus end exponent left parenthesis aq right parenthesis straight space plus straight space straight H to the power of plus straight space left parenthesis aq right parenthesis straight space rightwards arrow

Or

State reasons for the following:

(i) Cu (I) ion is not stable in an aqueous solution.

(ii) Unlike Cr3+, Mn2+, Fe3+ and the subsequent other M2+ ions of the 3d series of elements, the 4d and the 5d series metals generally do not form stable cationic species.

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 Multiple Choice QuestionsLong Answer Type

353.

(a) Complete the following equations :
(i) Cr2O72- + 2OH- --->
(ii) MnO4- + 4H+ + 3e- --->

(b) Account for the following :
(i) Zn is not considered as a transition element.
(ii) Transition metals form a large number of complexes.
(iii) The E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+ couple.

OR

(i) With reference to structural variability and chemical reactivity, write the differences between lanthanoids and actinoids.

(ii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.
(iii) Complete the following equation :
MnO4- + 8H+ + 5e---->
iv) Mn3+ is more paramagnetic than Cr3+.

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 Multiple Choice QuestionsShort Answer Type

354.

Write the formula of an oxo-anion of Manganese (Mn) in which it shows the oxidation state equal to its group number.

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355.

What happens when
(NH4)2Cr2O7 is heated?

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356.

Account for the following :
Transition metals form large number of complex compounds.

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357.

Account for the following :
The lowest oxide of transition metal is basic whereas the highest oxide is
amphoteric or acidic.

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358.

Account for the following :
E° value for the Mn3+/Mn2+ couple is highly positive (+1.57 V) as compared to Cr3+/Cr2+.


Mn2+ exists in 3d5 configuration which is a half-filled configuration which provides extra stability to the Metal Ion. While Mn3+ will exist in 3d4 configuration which is less stable than 3d5. Hence the conversion from 3+ to 2+ is very feasible. Hence E° value is more. while in

 Cr+3 exist in 3d3 half-filled d orbital (3 e; electrons in t2g ) extra stability is attained by Cr+3 than Cr+2. Hence Cr+3 →Cr+2 is less feasible. And hence it has less reduction potential as compare to Mn+3/Mn+2.

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359.

Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

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360.

Out of Cu+ and Cu2+, which ion is unstable in aqueous solution and why?

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