Respostas
Resposta:
Chemical transformations occur all the time around us, for example it is very common to notice that metallic materials such as fences, gates, nails, among others, when exposed to the environment end up deteriorating. This is due to the contact of the chemical element iron (Fe) with oxygen atoms (O) present in atmospheric air and water. We can also notice that in coastal regions these materials suffer even more damage due to the presence of salts and a higher humidity.

Rusty padlock. Photo: sezer66 / Shutterstock.com
This phenomenon is known as rust and occurs due to an oxidation reaction. But what is an oxidoreduction reaction? This type of reaction occurs when electrons are transferred between the atoms involved. And in this case the substance that receives electrons is reduced and consequently is the oxidizing agent; and whoever loses electrons gets oxidized and is the reducing agent. And we must always remember that one process does not occur without the other, that is, they are dependent.
In the case of rust, the oxidizer (reducing agent) is iron and this occurs according to the reactions below:
Explicação:
Fe (s) → Fe2 + + 2e- (oxidation of iron)
O2 + 2H2O + 4e- → 4OH- (oxygen reduction)
2Fe + O2 + 2H2O → 2Fe (OH) 2 (general equation)
In the first reaction we have the oxidation of iron, then the reduction of oxygen. Then the global equation or reaction is shown.
However, there are very practical ways of preventing iron materials from being attacked, one of which is to make it impossible for water and air to come into contact with metal through waterproofing using paint or oil.