Identify the element reduced in following reaction.

$$\mathrm{Cr}_2 \mathrm{O}_7^{2-}+14 \mathrm{H}^{+}+6 \mathrm{I}^{-} \longrightarrow 2 \mathrm{Cr}^{3+}+3 \mathrm{H}_2 \mathrm{O}+3 \mathrm{I}_2$$

What is the oxidation number of underlined species in $\mathrm{PF}_6^{-}$and $\mathrm{V}_2 \mathrm{O}_7^{-4}$ ions respectively?

Which among the following species is reduced by tin easily?

What is the number of moles of electrons gained by one mole oxidizing agent in following redox reaction?

$$\mathrm{Zn_{(s)}+2HCl_{(aq)}}$$ $$\longrightarrow$$ $$\mathrm{ZnCl_2+H_2}$$