Which of the following characteristics of the transition metals is associated with their catalytic activity?

Which one of these is not known?

Which of the following will not form an amalgam?

$(a)$ 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.

Which of the following are basic oxides among $Mn_2O_7 (I)$,$V_2O_3 (II)$,$V_2O_5 (III)$,$CrO (IV)$,and $Cr_2O_3 (V)$?

Explain the catalytic properties of transition metals.