Question

Which of the following is more stable form of iron in an oxygenated solution?

(a) Fe2O3

(b) Fe(OH)2

(c) 2Fe(OH)3

(d) Fe3O4

I had been asked this question in a national level competition.

This interesting question is from Corrosion Principles topic in portion Corrosion Principles of Corrosion Engineering

Answer 1

The correct option is (c) 2Fe(OH)3

The best explanation: +3 oxidation state of iron is more stable state of iron than +2 oxidation state. The reaction is follows as

Fe+H2O+½O2==>Fe(OH)2

2Fe(OH)2+H2O+1/2O2==>2Fe(OH)3.