Question

Which of the following is most corroded in moist air?
A. Zn
B. Fe
C. Ni
D. Sn

Answer 1

Hint: Corrosion is defined as the process through which the refined metals are converted into more stable compounds such as metal oxides, metal sulfides or metal hydroxides. It is usually an undesirable phenomenon since it negatively affects the desirable properties of metal.

Complete step by step answer:
Corrosion is a spontaneous/ irreversible process wherein the metals turn into a much stable chemical compound like oxides, sulphides, hydroxides etc. Metals placed higher in the reactivity series such as iron, zinc get corroded very easily whereas the metals placed lower in the reactivity series like gold, platinum and palladium do not corrode.
Among the given options, Fe is most corroded in moist air. When it is exposed to the moist air, it reacts with oxygen to form rust.
Moreover, oxygen is a highly active oxidizing agent whereas iron is a reducing agent. Therefore, the iron atom immediately gives up the electrons when exposed to oxygen. The reactions taking place are given below:
 $Fe \to F{e^{2 + }} + 2{e^ - }$
Further, the oxidation state of iron is increased by the oxygen atom when water is present in the atmosphere.
 $4F{e^{2 + }} + 4{H^ + } + {O_2} \to 4F{e^{3 + }} + 2{H_2}O$

Hence, option B is correct.

Note: Preventing corrosion is of utmost importance in order to avoid huge losses. Various methods to prevent corrosion are electroplating, cathodic protection, Galvanization, Painting and Greasing and using corrosion inhibitors.