What is rusting electrochemical theory?, Chemistry

Assignment Help:

According to this theory, the impure iron surface behaves like a small electrochemical cell presence of water containing dissolved oxygen or carbon dioxide. Such a cell is also called corrosion cell or corrosion couple. In these miniature corrosion cells, pure iron acts as anode and impure surfaces acts as cathode. Moisture dissolved oxygen or carbon dioxide in it comprises electrolytic solution.


At anode, oxidization of Fe atoms takes place. Thus, Fe atoms pass into solution as Fe2+ ions leaving behind electrons in the metal which are pushed into cathodic area.
                                              
Fe  2370_halides.png  Fe+2 + 2e-;  604_Rusting theory.png = - 0.44 V        (i)


At cathode, the electrons are picked up by the H+ ions which are produced either from H2O or from H2CO3 (formed by dissolution of CO2in moisture).
                                 
CO2 + H2O  2370_halides.png  H+ + HCO3-
                           
2H+(aq) + 2e-  2370_halides.png  2H


The H atoms, thus, formed, reduce the dissolved oxygen as
                                 
2H + ½ O2  2370_halides.png  H2O

The net reduction process at the cathodic area is
                        
2H + ½ O2 + 2e-  2370_halides.png  H2O; 1581_Rusting theory1.png = 1.23 V                      (ii)


The net reaction of the corrosion cell can be obtained by adding equations (i) and (ii)
                                     
F2 + 2H+  2370_halides.png   ½O2 
                               
2 Fe2+ + H2O;  = 1.67 V


The ferrous ions so formed move through water and come at the surface of iron object where these are further oxidized to ferric state by atmospheric oxygen and constitute rust which is hydrated iron (III) oxide.
                  
2Fe2+ + ½ O2 + 2H2O  2370_halides.png  Fe2O3 + 4H+
                                 
Fe2+ + xH2O  2370_halides.png  Fe2O3xH2O (rust)

 

 

 

 

 


Related Discussions:- What is rusting electrochemical theory?

The number of quantum numbers required describe an electron, The number of ...

The number of quantum numbers required to describe an electron in an atom completely is: (1) 1          (2) 2         (3) 3     (4) 4 Ans: 4

Mole concept , what is the relation between gram atomic mass and avogadro'...

what is the relation between gram atomic mass and avogadro''s no ?

Assingment, introduction of chemical bond

introduction of chemical bond

Calculate the mole fraction of nh3, What will happen if you mix nitrogen an...

What will happen if you mix nitrogen and hydrogen gas at room temperature? Explain your reasoning. Calculate the mole fraction of NH 3 that would form theoretically at 298.15

Isolation and purification of metals, Q. Isolation and purification of meta...

Q. Isolation and purification of metals? metals as a group of elements have acquired a unique importance in the modern world. However, nature' does not generally offer us metal

The magnetic quantum number specifies, The magnetic quantum number specifie...

The magnetic quantum number specifies : (1) Size of orbitals (2) Shape of orbitals (3) Orientation of orbitals (4) Nuclear stability Ans:   Orientation of orbitals

Chemistry, importance of chemistry in computer engineering

importance of chemistry in computer engineering

Miller indices of the diagonal plane of a cube, Miller indices of the diago...

Miller indices of the diagonal plane of a cube are   (110)

Quantitative elemental analysis, Quantitative elemental analysis: The ...

Quantitative elemental analysis: The instrument used for AFS consists of atom reservoir that might be a flame or a furnace etc., a basic source emitting the features absorptio

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd