Question

In corrosion of iron:
A. An electrochemical reaction (galvanic cell) is formed in which $Fe$acts as anode and cathode is where ${O_2}$ is reduced.
B. Electrons flow from anode to cathode through the metal while ions flow through the water-droplets.
C. Dissolved ${O_2}$ oxidizes $F{e^{2 + }}$ to $F{e^{3 + }}$ before it is deposited as rust ($F{e_2}{O_3}.{H_2}O$)
D. All of the above takes place

Answer 1

Hint: We have studies about galvanic cells. It is an electro-chemical cell that generates electrical energy from spontaneous redox reactions taking place inside the cell. It is also called a voltaic cell. Also, we know the corrosion process. It is a process through which metals deteriorate when exposed to oxygen.

Complete step by step answer:
A galvanic cell consists of two different metals immersed in electrolytes of the same metals in aqueous solution. The ions are connected by a salt bridge, separated by a porous membrane.
Galvanic corrosion is an electrochemical process of erosion of metals.
We know that corrosion generally occurs when two dissimilar metals are in contact with each other in the presence of electrolyte like salt water. The hydrogen gas is formed on the more noble or less active metal. Thus, the resulting electrochemical potential develops an electric current that dissolves the less active metal electrochemically.
When iron corrodes, it forms a reddish-brown coloured metal oxide which is represented by a chemical formula - $F{e_2}{O_3}.{H_2}O$. This oxide is called rust. This rust flakes off from the surface of iron to expose the fresh metal surface for oxidation.
In corrosion, iron metal acts as an anode in a galvanic cell. It is oxidized to $F{e^{2 + }}$.
At cathode, the oxygen is reduced to water.
The following reaction takes place,
At anode-
$F{e_{(s)}} \to Fe_{(aq)}^{2 + } + 2{e^ - }$
At cathode-
${O_{2(g)}} + 4H_{(aq)}^ + + 4{e^ - } \to 2{H_2}{O_{(l)}}$
The $F{e^{2 + }}$ ion produced at anode is oxidized by dissolved oxygen to $F{e^{3 + }}$before forming rust.
The electrons in the solute flows from anode to cathode through metals, while the ions flow through water droplets.
From this study, we can observe that in the iron corrosion process, all the processes take place.

So, the correct answer is Option D.

Note: We should remember that the oxidation of many metals is a thermodynamic spontaneous process except for gold and platinum. To prevent corrosion, we can apply an anti-corrosive layer of another material which can or cannot be a metal. Like if we apply paint, it can prevent corrosion. This is the simplest and the efficient way which is practiced in day-to-day life, everywhere around us. The paint acts as a protective layer, allowing no room for oxygen to enter.