Answer the questions based on the passage given below:

Adsorption is a surface phenomenon and it differs from absorption which occurs throughout the body of the substance that absorbs. In physisorption the attractive forces are mainly van der Waals forces while in chemisorption ionic / covalent bonds are formed between particles of adsorbent and adsorbate. The catalytic activity of finely divided iron in Haber's process of ammonia manufacture can be explained by adsorption theory. Adsorption being an exothermic process, the heat of adsorption is utilized in enhancing the rate of the reaction. Adsorption has many applications being used in gas masks, control of humidity, chromatograph separation, curing diseases etc.

Which of the following is not a surface phenomenon?

Electrolytic process

The correct answer is option 4. Electrolytic process.

An electrolytic process involves the use of electrical energy to drive non-spontaneous chemical reactions, typically carried out in an electrolytic cell. In this process, electrical current is passed through an electrolyte solution, causing chemical changes at the electrodes.

Electrolyte Solution: The reactions occur in a solution containing ions, not just at the surface of the electrodes.

Electrodes: The reactions at the electrodes (anode and cathode) are indeed surface phenomena because the exchange of electrons and the associated chemical reactions occur at the electrode surfaces. However, the overall process includes both the bulk solution and the surface interactions at the electrodes.

Surface vs. Bulk Phenomena:

Surface Phenomenon: Involves interactions occurring specifically at interfaces, such as surface reactions, adsorption, and catalysis on solid surfaces.

Bulk Phenomenon: Involves interactions within the bulk of the material, including processes that involve the entire volume or large parts of a substance, such as melting (fusion) and electrolytic processes in solution.

Conclusion:

Electrolytic Processes involve both the bulk electrolyte and surface reactions at the electrodes. While the surface interactions are critical, the overall process is not confined to just surface phenomena but also includes the entire electrolyte solution.  Thus, considering the broader scope of the electrolytic process, the correct understanding is that it is not solely a surface phenomenon but includes interactions beyond just the surface.

So the accurate answer is option 4: Electrolytic Process.