Question

Rusting of iron is catalyzed by which of the following:
A)$\text{ Fe }$
B) $\text{ Zn }$
C) $\text{ }{{\text{O}}_{\text{2}}}\text{ }$
D) $\text{ }{{\text{H}}^{\text{+}}}\text{ }$

Answer 1

The rusting is a process of formation of a layer of oxide on the metal surface. The common example is the rusting of iron. The rate of rusting of iron is controlled by the rate of evolution of hydrogen gas at the metallic surface.

Complete step by step answer:
The rusting is defined as the formation of the rust, iron oxides on the surface of the object. The formation of rust is a redox reaction between the oxygen and the water from the environment (moisture).
Rust is an iron oxide. These are a hydrated iron (III) oxide having the general formula as$\text{ F}{{\text{e}}_{\text{2}}}{{\text{O}}_{\text{3}}}\text{ }\text{.n}{{\text{H}}_{\text{2}}}\text{O }$. The iron exhibits the two different valencies $\text{ + 2 }$ and$\text{+3}$. Therefore, we observe the two types of iron oxides which are ferrous oxide and ferric oxide.
The rusting is a corrosion of the metal surface. The metal reacts with the moisture from the surrounding, the metal at the surface oxides to form a layer of metal oxide. These layers prevent the further corrosion of the metal and result in the slow disintegration of metal due to the rusting.
The general reaction of the oxidation of iron is given as follows,
$\text{ Fe }\to \text{ Fe}{{\text{ }}^{\text{2+}}}\text{ + 2}{{e}^{-}}\text{ }$
There are several other cathode reactions. But there is a one cathode reaction that controls the corrosion rate. the reaction is as shown below,
$\text{ 2}{{\text{H}}^{\text{+}}}\text{ + 2}{{e}^{-}}\to \text{ }{{\text{H}}_{\text{2}}}\text{ }$
The usual rate of corrosion is slow. But in the presence of$\text{ }{{\text{H}}^{\text{+}}}\text{ }$. The rate of corrosion depends on how fast the hydrogen gas is discharged at the cathode. The $\text{ pH }$is responsible for the catalytic property of the corrosion of iron. This property is measured by the potential difference of the cathode and the equilibrium potential of a hydrogen electrode in the same solution. This difference in the potential is called the hydrogen overvoltage.
The platinum, copper, and iron are the best catalytic surfaces that have the cathodic reduction of oxygen. The reduction is rapid in presence of an acid medium. It is so rapid that all the oxygen which is reaching to iron immediately reacts and increases the rate of corrosion.
Rusting of iron is catalyzed by the acidic medium (in presence of $\text{ }{{\text{H}}^{\text{+}}}\text{ }$ ions). Therefore, the $\text{ }{{\text{H}}^{\text{+}}}\text{ }$ions in the solution catalyse the rusting of iron.

Hence, (D) is the correct option.

Note: The rusting of iron is considered as the demerit of the metal. But we have procedures which can be utilized to prevent the rusting of metal. One of the techniques is galvanization. The galvanization is a process of coating iron with the zinc. The zinc retains on the metal surface as it is protected from the layer of hydrated oxide. Another method involves the coating of metal with an impermeable layer (such as paint) which prevents exposure to the damp air.