Question
Which of the following processes does not involve oxidation of iron?
A.
Rusting of iron sheets
B.
Decolourisation of blue $$CuS{O_4}$$ solution by iron
C.
Formation of $$Fe{\left( {CO} \right)_5}$$ from $$Fe$$
D.
Liberation of $${H_2}$$ from steam by iron a high temperature
Answer :
Formation of $$Fe{\left( {CO} \right)_5}$$ from $$Fe$$
Solution :
$$\eqalign{
& \left( {\text{A}} \right)\mathop {Fe}\limits^0 + \underbrace {{H_2}O + {O_2}}_{{\text{from}}\,\,{\text{air}}} \to \mathop F\limits^{{\text{III}}} {e_2}{O_3} \cdot x{H_2}O \cr
& \left( {\text{B}} \right)\mathop {Fe}\limits^0 + CuS{O_4} \to \mathop {Fe}\limits^{{\text{II}}} S{O_4} + Cu \cr
& \left( {\text{C}} \right)\mathop {Fe}\limits^0 + 5CO \to \mathop {Fe}\limits^0 {\left( {CO} \right)_5} \cr
& \left( {\text{D}} \right)\mathop {Fe}\limits^0 + \mathop {{H_2}O}\limits_{{\text{Stream}}} \to \mathop F\limits^{{\text{III}}} {e_2}{O_3} + {H_2} \cr} $$
∴ Formation of $$Fe{\left( {CO} \right)_5}$$ from $$Fe$$ does not involve oxidation of iron because there is no change in oxidation state.