$E^{\ominus}$ values of some redox couples are given below. On the basis of these values choose the correct option.

$$\begin{aligned} E^{\ominus} \text { values: } \mathrm{Br}_2 / \mathrm{Br}^{-} & =+1.90 \\ \mathrm{Ag}^{+} / \mathrm{Ag}(s) & =+0.80 \\ \mathrm{Cu}^{2+} / \mathrm{Cu}(s) & =+0.34 ; \mathrm{I}_2(s) / \mathrm{I}^{-}=+0.54 \end{aligned}$$

Using the standard electrode potential, find out the pair between which redox reaction is not feasible.

$$\begin{aligned} & E^{\ominus} \text { values: } \mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}=+0.77 ; \mathrm{I}_2 / \mathrm{I}^{-}=+0.54 ; \\ & \mathrm{Cu}^{2+} / \mathrm{Cu}=+0.34 ; \mathrm{Ag}^{+} / \mathrm{Ag}=+0.80 \mathrm{~V} \end{aligned}$$

Thiosulphate reacts differently with iodine and bromine in the reactions given below

$$\begin{gathered} 2 \mathrm{~S}_2 \mathrm{O}_3^{2-}+\mathrm{I}_2 \rightarrow \mathrm{S}_4 \mathrm{O}_6^{2-}+2 \mathrm{I}^{-} \\ \mathrm{S}_2 \mathrm{O}_3^{2-}+2 \mathrm{Br}_2+5 \mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{SO}_4^{2-}+2 \mathrm{Br}^{-}+10 \mathrm{H}^{+} \end{gathered}$$

Which of the following statements justifies the above dual behaviour of thiosulphate?

The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following is incorrect in this respect?

In which of the following compounds, an element exhibits two different oxidation states?