How many moles of acidified $$\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$$ is required to liberate 6 moles of $$\mathrm{I}_2$$ from an aqueous solution of $$\mathrm{I}^{-}$$?

The oxidation number of nitrogen atoms in $$\mathrm{NH}_4 \mathrm{NO}_3$$ are

In which of the following cases a chemical reaction is possible?

The number of moles of electron required to reduce 0.2 mole of $$\mathrm{Cr}_2 \mathrm{O}_7^{-2}$$ to $$\mathrm{Cr}^{+3}$$ is