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  • (a) The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co Ni Cu Zn Answer the following (i) Copper has exceptionally positive <img alt="E^{0}\left ( M^{2+}/M \right )" src="https://entrancecorner.codecogs.com/gif.l

(a) The elements of 3d transition series are given as:
Sc Ti V Cr Mn Fe Co Ni Cu Zn
Answer the following
(i) Copper has exceptionally positive E^{0}\left ( M^{2+}/M \right ) value Why?
(ii) Which element is a strong reducing agent in +2 oxidation state and Why?
(iii) zn2+ salts are colourless. Why?
(b) Write the preparation of sodium dichromate from chromite ore(FeCr2O4).

 

 

 

 
 
 
 
 

Answers (1)

(a) (i) On has exceptionally positive E0m2+/m value because 2nd e- has to be removed from extra stable fully filled configuration 3d10. The low value of \Delta H_{nyd} cannot compensate the high energy required to transform Cu to Cu2+.
(ii) Cr is a strong reducing agent in +2 oxidation state , it havy nearly easily loss e- to achieve its highest oxidation state of +6 to become extra stable.
(iii) zn2+ salts are colourless because zn2+ doesnot have unpaired electrons, it has fully filled d-orbital and unpaired excite to give colour to compounds.
(b) preparation of Na2Cr2O7 from FeCr2O4
4FeCr_{2}O_{4}+8Na_{2}CO_{3}+7O_{2}\rightarrow 8Na_{2}CrO_{4}+2Fe_{2}O_{3}+8CO_{2}
Chromire ore
2Na_{2}CrO_{4}+H_{2}SO_{4}\rightarrow Na_{2}Cr_{2}O_{r}+Na_{2}SO_{4}+H_{2}O
                                                        sodium dichromate

Posted by

Sumit Saini

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