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Explain the process involved in corrosion. |
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Answer» 1) Corrosion is an electrochemical phenomenon. 2) In corrosion, a metal is oxidised by loss of electrons generally to oxygen and results in the formation of oxides. 3) During corrosion at a particular spot on the surface of an object made of iron, oxidation takes place and that spot behaves as anode. Anode : 2 Fe(s) → 2 Fe2+ + 4e- 4) Electrons released at this anodic spot move through the metal and go to another spot and reduce oxygen at that spot in the presence of H+. 5) This spot behaves as cathode. Cathode : O2(g) + 4 H+(aq) + 4e- → 2H2O(I) Net reaction : 2 Fe(s) + O2(g) + 4 H+(aq) → 2 Fe2+(aq) + 2 H2O(I) 6) The ferrous ions are further oxidised by atmospheric oxygen to ferric ions which come out as rust in the form of hydrated ferric oxide (Fe2O3 . XH2O) and with further production of hydrogen ions. |
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