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 type of orbitals present in fe is, The type of orbitals present in Fe ...

The type of orbitals present in Fe  is : (1) s                       (2) s  and p     (3)  s, p and d            ()s, p, d, and f Ans: s, p and d

Standard molar reaction enthalpy and temperature dependence, Q: For a homog...

Q: For a homogeneous reaction in which the reactants and products are solutes in a solution, write a rigorous relation between the standard molar reaction enthalpy and the temperat

P-block, oxidation state of p-block elements?

oxidation state of p-block elements?

Determine the electronic configurations, Aufbau principle is obeyed in whic...

Aufbau principle is obeyed in which of the following electronic configurations: (1) 1s 2 2s 2 2p 6                    (2)  1s 2 3p 6 3s 2      (3)  1s 2 3s 2 3p 6

Chlorobenzene, Formation of aniline from chlorobenzene

Formation of aniline from chlorobenzene

What concentration of b alone is increased to three times, A reaction is of...

A reaction is of first order in reactant A and of second order in reactant B. How is the rate of this reaction affected when (i) the concentration of B alone is increased t

Beilstein test or copper wire test - halogens, Beilstein test or copper wi...

Beilstein test or copper wire test  - Halogens A clean copper wire is heated in the Bunsen flame till it does not impart any type of green colour to the flame. The heated side

Mole concept, The difference in the mass of 100 moles of sodium atoms and s...

The difference in the mass of 100 moles of sodium atoms and sodium ions is 5.48002grams .compute the mass of an electron

Show the reactions of boric oxide, Q. Show the Reactions of Boric Oxide? ...

Q. Show the Reactions of Boric Oxide? Boric oxide, B 2 0 3 , is the principal oxide of boron. It is also known as boron trioxide, boron sesquioxide and boric anhydride. It is p

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