$(a)$ Transition metals can act as catalysts because these can change their oxidation state. How does $Fe(III)$ catalyse the reaction between iodide and persulphate ions ?
$(b)$ Mention any three processes where transition metals act as catalysts.
$(a)$ Reaction between iodide and persulphate ions is given by $2 \mathrm{I}^{-}+\mathrm{S}_{2} \mathrm{O}_{8}^{2-} \stackrel{\mathrm{Fe}(\mathrm{III})}{\longrightarrow} \mathrm{I}_{2}+2 \mathrm{SO}_{4}^{2-}$
Mechanism :
$(i)$ $2 \mathrm{Fe}^{3+}+2 \mathrm{I}^{-} \rightarrow 2 \mathrm{Fe}^{2+}+\mathrm{I}_{2}$
$(ii)$ $2 \mathrm{Fe}^{2+}+2 \mathrm{~S}_{2} \mathrm{O}_{8}^{2-} \rightarrow 2 \mathrm{Fe}^{3+}+2 \mathrm{SO}_{4}^{2-}$
$(b)$ $(i)$ Contact process : $\mathrm{V}_{2} \mathrm{O}_{5}$
$(ii)$ Haber's process : Finely divided : Fe
$(iii)$ Decomposition of $\mathrm{KClO}_{3}: \mathrm{MnO}_{2}$
Which of the following metals make the most efficient catalyst
The correct order of decreasing third ionisation enthalpy of $Ti, \,V,\, Cr,\, Mn$ is
Which one of the following statements shows the correct percentage of carbon in steel, pig iron and wrought iron
The fusion of chromite ore with sodium carbonate in the presence of air leads to the formation of products $\mathrm{A}$ and $\mathrm{B}$ along with the evolution of $\mathrm{CO}_2$. The sum of spin-only magnetic moment values of $A$ and $B$ is .......... $B.M.$ (Nearest integer)
(Given atomic number: $\mathrm{C}: 6, \mathrm{Na}: 11, \mathrm{O}: 8$, $\mathrm{Fe}: 26, \mathrm{Cr}: 24 \mathrm{~J}$
Which have melting point below $500\,^{\circ} C$.