question_answer

\[Mn{{O}_{4}}^{2-}\] undergoes disproportionation reaction in acidic medium but \[Mn{{O}_{4}}^{-}\] does not because

A) In \[Mn{{O}_{4}}^{2-}Mn\] is in intermediate oxidation state

B) In \[Mn{{O}_{4}}^{2-},Mn\] is in lowest oxidation state

C) In \[Mn{{O}_{4}}^{2-},Mn\] is in intermediate oxidation state

D) None of the above

Correct Answer: A

Solution :

[a] In \[Mn{{O}_{4}}^{2-},\] the oxidation number of\[Mn\] is + 6. It can increase its oxidation number (to + 7) or decrease its oxidation number (to + 4, + 3, + 2, 0). Hence it undergoes disproprotion rection is acidic medium.

In \[Mn{{O}_{4}}^{-},Mn\] is in its highest oxidation state i.e., +7. It can only decrease its oxidation number. Hence, it cannot undergo disproportionation reaction.