Question

Which of the following statement is correct regarding rusting of iron?

• A. It can take place in the absence of oxygen
• B. It can take place in presence of either oxygen or water
• C. Both water and oxygen are required for rusting of iron
• D. None of the above

Answer 1

The correct option is C Both water and oxygen are required for rusting of iron

Rusting of Iron may be considered as an electrochemical phenomenon. It occurs in presence of both, moisture and oxygen.

Rusting of Iron
$2Fe\left(s\right)+\frac{3}{2}{O}_2\left(g\right)+x{H}_{2}O\left(l\right)\rightleftharpoons F{e}_2{O}_3.x{H}_{2}O\left(s\right)$

Theory :

Here we can see that both air (oxygen) and water are required for rusting. In the first case(from left) both are present and hence rusting take place but in the middle test tube air contact is deprived due to oil layer. Although water is present but oxygen is also needed for rusting. In the right most test tube, anhydrous $CaC{l}_2$ absorbs all the moisture from the air, and thus due to absence of water rusting do not take place.