The d-and f-Block Elements — Chemistry STD 12 Science — Question
Bihar BoardEnglish MediumSTD 12 ScienceChemistryThe d-and f-Block Elements2 Marks
Question
Explain Catalytic property of transition element.
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Answer
→ The transition metals and their compounds are known for their catalytic activity. → This activity is ascribed to their ability to adopt multiple oxidation states and to form complexes. → Vanadium (V) oxide (in Contact Process), finely divided iron (in Haber's Process), and nickel (in Catalytic Hydrogenation) are some of the examples. → Catalysts at a solid surface involve the formation of bonds between reactant molecules and atoms of the surface of the catalyst (first row transition metals utilise 3d and 4s electrons for bonding). → This has the effect of increasing the concentration of the reactants at the catalyst surface and also weakening of the bonds in the reacting molecules (the activation energy is lowering). → The Transition metal ions can change their oxidation states, they become more effective as catalysts. → For example, iron (III) catalyses the reaction between iodide and persulphate ions. $ 2 I ^{-}+ S _2 O _8^{2-} \rightarrow I _2+2 SO _4^{2-} $ → An explanation of this catalytic action can be given as : $ \begin{array}{l} 2 Fe ^{3+}+2 I ^{-} \rightarrow 2 Fe ^{2+}+ I _2 \\ 2 Fe ^{2+}+ S _2 O _8^{2-} \rightarrow 2 Fe ^{3+}+2 SO _4^{2-} \end{array} $
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