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(a) Account for the following:
(i) Mn2O7 is acidic whereas MnO is basic.
(ii) Zr and Hf exhibit similar properties.
(iii) Transition metals form a large number of complex compounds.
(b) Write the preparation of K2MnO4 from pyrolusite ore(MnO2). Write the type of magnetism shown by KMnO4 and K2MnO4.

 

 

 

 
 
 
 
 

Answers (1)

(a) (i) Mn2O is acidic but MnO is basic because in Mn2O4 , oxidation state of Mn is +7 \therefore Those oxide are covalent, due to higher charge it on accept electrons whereas in MnO, Mn is m +2 oxidation state and bring ionic they produce base in turn gives OH ions in solution
(ii) zn and Hf exhibit similar properties since there is an overall decrease in atomic radic of element of f-electrons which is unable to counter balance effect of increased nuclear charge
(iii) trasition metals can form large number of compounds due to presence of valence electrons in two different sets of orbitals ie outer ns and (n-1)d Both of them can get involved in bend formation due to small energy difference between them, they can show variable oxidation state.
(b) Preperation of K2MnO4 from MnO2
2MnO_{2}+4KoH+O_{2}\rightarrow 2K_{2}MnO_{4}+2H_{2}O
Black                                                Dark Green
K2MnO4 is paramagnetic and KMnO4 is diamagnetic.

Posted by

Sumit Saini

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