Number of moles of $$\mathrm{H}^{+}$$ ions required by $$1 \mathrm{~mole}$$ of $$\mathrm{MnO}_4^{-}$$ to oxidise oxalate ion to $$\mathrm{CO}_2$$ is _________.

Total number of species from the following which can undergo disproportionation reaction is ________.

$$\mathrm{H}_2 \mathrm{O}_2, \mathrm{ClO}_3^{-}, \mathrm{P}_4, \mathrm{Cl}_2, \mathrm{Ag}, \mathrm{Cu}^{+1}, \mathrm{~F}_2, \mathrm{NO}_2, \mathrm{K}^{+}$$

$$2 \mathrm{MnO}_4^{-}+\mathrm{bI}^{-}+\mathrm{cH}_2 \mathrm{O} \rightarrow x \mathrm{I}_2+y \mathrm{MnO}_2+z \overline{\mathrm{O}} \mathrm{H}$$

If the above equation is balanced with integer coefficients, the value of $$z$$ is ________.

The oxidation number of iron in the compound formed during brown ring test for NO$$_3^-$$ iron is ________.