(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): 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)
- Catalyst is the inert chemical species which increases the rate of reaction without taking part in the reaction.
- Transition metal can show variable oxidation state due to small energy gaps between ns and (n−1)d subshells.
- Due to the small energy gap, electrons of both subshells take part in oxidation and reduction reactions. Thus, transition metal acts as a catalyst.
- The reaction between iodide and persulfate ions in presence of Fe(III) is written below:
2l−+S2O2−3Fe(III)−−−−−→CatalystI2+2SO2−4
The role of Fe(III) in this reaction is described below:
(i) In the first step, Fe(III) acts as an oxidising agent and oxidises the iodide ion to iodine and reduce itself to Fe(II).
2I−+2Fe3+→I2+2Fe2+
(ii) In the second step, Fe(II) acts as a reducing agent and reduces the persulfate ion and oxidizes itself to Fe(III).
2Fe2++S−2O2−8→2SO2−4+2Fe3+
(B):
Reactions where transition metals act as catalysts:
Haber′s process:
Finely divided iron is used as a catalyst in Haber’s process which is used for manufacturing of ammonia.
IronOxideN2(g)+3H2(g) ⇌ 2NH3(g)
Contact process:
V2O5 acts as a catalyst in the contact process which is used for the synthesis of H2SO4.
During this process sulphur dioxide and oxygen are passed over the catalyst such that SO2 gets oxidised to SO3
V2O52SO4 +O2 ⇌2SO3Catalyst
Decomposition of KClO3:
MnO2 is used as a catalyst in the preparation of oxygen from KClO3.
MnO2
2KClO3 ⇌ 2KCl+3O2
Catalyst
- Catalyst is the inert chemical species which increases the rate of reaction without taking part in the reaction.
- Transition metal can show variable oxidation state due to small energy gaps between ns and (n−1)d subshells.
- Due to the small energy gap, electrons of both subshells take part in oxidation and reduction reactions. Thus, transition metal acts as a catalyst.
- The reaction between iodide and persulfate ions in presence of Fe(III) is written below:
2l−+S2O2−3Fe(III)−−−−−→CatalystI2+2SO2−4
The role of Fe(III) in this reaction is described below:(i) In the first step, Fe(III) acts as an oxidising agent and oxidises the iodide ion to iodine and reduce itself to Fe(II).
2I−+2Fe3+→I2+2Fe2+
(ii) In the second step, Fe(II) acts as a reducing agent and reduces the persulfate ion and oxidizes itself to Fe(III).
2Fe2++S−2O2−8→2SO2−4+2Fe3+
(B):
Reactions where transition metals act as catalysts:
Haber′s process:
Finely divided iron is used as a catalyst in Haber’s process which is used for manufacturing of ammonia.
IronOxideN2(g)+3H2(g) ⇌ 2NH3(g)
Contact process:
V2O5 acts as a catalyst in the contact process which is used for the synthesis of H2SO4.
During this process sulphur dioxide and oxygen are passed over the catalyst such that SO2 gets oxidised to SO3
V2O52SO4 +O2 ⇌2SO3Catalyst
Decomposition of KClO3:
MnO2 is used as a catalyst in the preparation of oxygen from KClO3.
MnO2
2KClO3 ⇌ 2KCl+3O2
Catalyst
