Question

How would you prepare
(i) `K_(2)MnO_(4)` and `MnO_(2)`? (ii) `Na_(2)Cr_(2)O_(7)` from `Na_(2)CrO_(4)` ?

Answer 1

(i)`MnO_(2)` is fused with KOH in the presence of oxygen (air).
`4KOH+2MnO_(2)+O_(2) overset(Heat) to 2K_(2)MnO_(4)+2H_(2)O`
(ii) `2Na_(2)CeO_(4)` is treated with dilute `H_(2)SO_(4)`.
`2Na_(2)CrO_(4)+H_(2)SO_(4) to Na_(2)Cr_(2)O_(7)+Na_(2)SO_(4)+H_(2)O`