Step 1: Understanding the Question:
The goal is to identify which process involves physical adsorption (physisorption), which is characterized by weak intermolecular forces rather than chemical bonds.
Step 2: Detailed Explanation:
Physisorption occurs due to weak van der Waals forces. It is non-specific and reversible.
- Option A: Adsorption of \(NH_3\) on charcoal can involve dipole-dipole or hydrogen bonding, but it is often borderline; however, noble gases are the purest example of van der Waals interaction.
- Option B: Hydrogen on Nickel involves the breaking of H-H bonds and formation of Ni-H bonds (Chemisorption).
- Option C: Noble gases (He, Ne, Ar, etc.) are chemically inert. They cannot form chemical bonds easily. Therefore, their adsorption on solids occurs only through very weak van der Waals forces. This is a definitive example of physisorption.
- Option D: Oxygen on heated metals typically forms metal oxides (Chemisorption).
Step 3: Final Answer:
The adsorption of noble gases on a solid surface is a standard example of physisorption.