Oxides of Group 6 transition metals (Cr, Mo, W) in their highest oxidation state have the general formula MO 3 . These oxides are acidic and dissolve in strong alkali to form [ MO 4 ] 2 − ions. It

Question

Oxides of Group 6 transition metals (Cr, Mo, W) in their highest oxidation state have the general formula MO 3 ​ . These oxides are acidic and dissolve in strong alkali to form [ MO 4 ​ ] 2 − ions. It is observed that [ CrO 4 ​ ] 2 − is readily reduced, while [ MoO 4 ​ ] 2 − and [ WO 4 ​ ] 2 − are not easily reduced. Which of the following statements explain(s) this difference?

TestHub · Accepted Answer

Although in the p-block the lower oxidation states are favoured by the heavier members [due to inert pair effect), the opposite is true in the groups of d-block. For example. in group 6, Mo[VI] and W[VI] are found to be more stable than Cr[VI]. Thus Cr(VI) in the form of dichromate in acidic medium is a strong oxidising agent, whereas MoO 3 ​ and WO 3 ​ are not.

Chemistry - Complete d-block Question with Solution | TestHub

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