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?

Atomic Mass, why C-12 is taken as standard for atomic mass?

why C-12 is taken as standard for atomic mass?

Copper, stuck on a chemistry assignment i need a way to include the elctron...

stuck on a chemistry assignment i need a way to include the elctron configuration and chemical properties of copper into a oral that is also a sales pitch.

Write the reaction involved in phenol to salicyclic acid, Write the reactio...

Write the reactions and the conditions involved in the conversion of: a. Propene to 1-Propanol b. Phenol to Salicyclic acid

The frequency of yellow light having wavelength, The frequency of yellow li...

The frequency of yellow light having wavelength 600 nm is: (1) 5.0x10 14 Hz                 (2)  2.5 x 10 7 Hz        (3) 5.0x 10 7 Hz

Steric effect, steric effect affecting the end product of organic compound

steric effect affecting the end product of organic compound

Atomic structure, the value of charge on the oil droplets experimentally ob...

the value of charge on the oil droplets experimentally observed were -1.6*10-19 and -4*10-19coulomb. the value of the electronic charge,indicated by these results is

Substrate concentration , How does the substrate concentration affect the s...

How does the substrate concentration affect the speed of enzymatic reactions? Ans) Initially as substrate concentration enhances the speed of the reaction enhances, this happens

Define product process problem in experimental design method, Define Produc...

Define Product process problem in experimental design method In food product design, there are two different kinds of system problems - process and mixture problems - that shou

Smell - physical characteristics of carbonyl compounds, Smell - Physical ch...

Smell - Physical characteristics of carbonyl compounds Along with the exception of lower aldehydes that have unpleasant odours, aldehydes and ketones have usually pleasant smel

Reaction intermediates, Reaction Intermediates Short lived fragments th...

Reaction Intermediates Short lived fragments that are known as reaction intermediates result from homolytic and heterolytic bond fission. The significant reaction substances ar

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