Which of the following is the correct order of negative values of $E^o\,M^{2+} | M$ for the elements $Cr, Mn, Fe,$ and $Co$?

The set of correct statements is:
$(i)$ Manganese exhibits $+7$ oxidation state in its oxide.
$(ii)$ Ruthenium and Osmium exhibit $+8$ oxidation state in their oxides.
$(iii)$ $Sc$ shows $+4$ oxidation state which is oxidizing in nature.
$(iv)$ $Cr$ shows oxidizing nature in $+6$ oxidation state.

$(a)$ Transition metals can act as catalysts because they can change their oxidation state. How does $Fe(III)$ catalyze the reaction between iodide and persulphate ions?
$(b)$ Mention any three processes where transition metals act as catalysts.

Concentrated sodium hydroxide can separate a mixture of

Transition metal with low oxidation number will act as

Discuss the catalytic properties of transition elements.