Class 12 NEET Chemistry D And F Block Elements Questions

Concept:Heating $\mathrm{KMnO_4}$ at 513 K causes a decomposition reaction that produces a green, paramagnetic manganate salt due to the presence of an unpaired electron in the manganese ion.Explanation:The thermal decomposition of $\mathrm{KMnO_4}$ follows the equation:$2\mathrm{KMnO_4} \rightarrow \mathrm{K_2MnO_4} + \mathrm{MnO_2} + \mathrm{O_2}$.The product $\mathrm{K_2MnO_4}$ contains manganese in the +6 oxidation state, which has a $d^1$ electronic configuration.This single unpaired electron makes the compound paramagnetic.The manganate ion ($\mathrm{MnO_4^{2-}}$) also imparts a characteristic green colour to the compound.Among the given options, only $\mathrm{K_2MnO_4}$ fits both the green colour and paramagnetic nature.$\mathrm{KO_2}$ is yellow‑orange, $\mathrm{Mn_3O_4}$ is black, and $\mathrm{MnO}$ is green but not paramagnetic and is not the primary product of this reaction at 513 K.Answer:Option B: $\mathrm{K_2MnO_4}$