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?

Molar conductivity, Molar conductivity: The rate of charge transfer is ...

Molar conductivity: The rate of charge transfer is proportional to the number of ions in the solution between the plates, which itself will vary with the concentration, c, of

Determine the impurities in the sample of oil, Q. Determine the impurities ...

Q. Determine the impurities in the sample of oil? After conducting this activity, you will be able to: • determine impurities such as total dirt and organic dirt in the giv

Determine mass of an electron, Q. Determine mass of an electron? Ans. ...

Q. Determine mass of an electron? Ans. Three years later after J.J Thomson discovered the electron, the American scientist Robert Millikan used an oil drop experiment to accu

Equivalent mass, x gram of metal reacts with chlorine to form y gram of met...

x gram of metal reacts with chlorine to form y gram of metal chloride.calculate equivalent mass of metal.

Uses of resorcinol, Uses of Resorcinol (a) Resorcinol is used as antise...

Uses of Resorcinol (a) Resorcinol is used as antiseptic and for creating dyes. (b) Resorcinol is also used in the medicine of eczema. 2, 4, 6-trinitroresorcinol is required

Electrochemical, I need a tutor for grad-level electrochemical specifically...

I need a tutor for grad-level electrochemical specifically cyclic voltammetry. Can you provide this?

Illustrate relative amount of two co-existing phases, Illustrate and demons...

Illustrate and demonstrate that, for correct mass balance, relative amount of two co-existing phases or micro constituents should be as given by lever rule. The lever rule giv

The number of radial nodes 3s and 2p orbitals respectively, The number of r...

The number of radial nodes of 3s and 2p orbitals are respectively : (1) 2, 0   (2) 0, 2          (3) 1, 2             (4) 2, 1 Ans: 2, 0

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