In acidic medium,iodide $(I^{-})$ is oxidized to iodine $(I_2)$ by $KMnO_4$. What is the change in the oxidation number of manganese in this reaction?

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$K_2Cr_2O_7 \xrightarrow{\Delta } K_2CrO_4 + Cr_2O_3 + O_2 \uparrow$

The number of electrons involved in the reduction of permanganate to manganese dioxide in acidic medium is $.......$.

If an iron rod is dipped in $CuSO_4$ solution,what happens?

In the reaction $2[Fe(CN)_6]^{3-} + H_2O_2 + 2OH^{-} \rightarrow 2[Fe(CN)_6]^{4-} + 2H_2O + O_2$,what is the equivalent weight of the reductant? $(Fe = 56, C = 12, N = 14, O = 16, H = 1)$

When $4$ moles of electrons are added to $NO_3^-$,the product obtained is .......