\(\quad \quad \quad \quad \quad \quad \quad Green\quad \quad \quad Black\)
In \({K}_{2} {MnO}_{4}\), manganese oxidation state is \(+6\) and hence it has one unpaired \({e}^{-}\).
$FeCr _{2} O _{4}+ Na _{2} CO _{3}+ O _{2} \rightarrow A + Fe _{2} O _{3}+ CO _{2}$
$A + H ^{+} \rightarrow B + H _{2} O + Na ^{+}$
(પરમાણ્વીય ક્રમાંક: $Ce = 58, Sm = 62,$$ Eu = 63, Yb = 70$)