This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Wet Theory of Corrosion”.
1. In wet corrosion, _________________ are formed at the cathodic areas.
a) Organic compounds
b) Metallic ions
c) Non-metallic ions
d) Inorganic compounds
Explanation: In wet corrosion, non-metallic ions are formed at the cathodic areas. Cathodes are negatively charged electrodes and attract positive charges or non-metallic ions.
2. Which type of reaction occurs at anodic areas?
Explanation: Oxidation occurs at anodic areas. Oxidation means addition of oxygen or removal of hydrogen.
3. Rusting of iron in neutral aqueous solution of electrolyte occurs in the presence of oxygen with the evolution of
Explanation: Rusting of iron in neutral aqueous solution of electrolyte occurs in the presence of oxygen with the evolution of hydrogen. Only hydrogen gas is evolved in this process.
4. Where does corrosion occurs in the rusting of iron?
a) At cathode
b) At anode
c) In electrolytic solution
d) Outside the solution
Explanation: Corrosion occurs at anode but rust is deposited near cathode.
5. Which of the following cathodic reaction does not occur due to release of electrons at the anode?
a) Oxygen absorption
b) Hydrogen evolution
Explanation: Oxygen absorption, hydrogen evolution and electroplating occur due to release of electrons at the anode.
6. Select the incorrect statement about the wet corrosion from the following option.
a) It involves the setting up of large number of galvanic cells
b) It is explained by absorption mechanism
c) It occurs only on heterogeneous metal surface
d) It is a fast process
Explanation: Wet corrosion is explained by mechanism of electrochemical reaction. All the other options are correct.
7. Which of the following factor does not contribute to the rusting of iron?
a) Presence of acids and electrolytes
b) Contact with less reactive metal
c) Presence of water and oxygen
d) Contact with more reactive metal
Explanation: Contact with more reactive metal does not contribute to the rusting of iron whereas all the other given factors contribute to the rusting of iron.
8. Concentration cell corrosion occurs when a metallic surface is partially immersed in an electrolyte and partially exposed to air.
Explanation: Concentration cell corrosion occurs when a metallic surface is partially immersed in an electrolyte and partially exposed to air. This is due to the the half part which is exposed to air. It gets in contact with air molecules and gets corroded.
9. Which of the following does not promote the differential aeration corrosion?
a) Accumulation of dirt
b) Partially covering metals
c) Wire fence kind of structures
d) Accumulation of oxygen
Explanation: Accumulation of dirt, partially covering metals and wire fence kind of structures are the factors which promote the differential aeration corrosion.
10. Poorly oxygenated part becomes cathode whereas well oxygenated part becomes anode in the differential aeration corrosion.
Explanation: Poorly oxygenated part becomes anode and undergoes oxidation whereas well oxygenated part becomes cathode in the differential aeration corrosion.
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