Adsorption

Given:

• Work needed to decrease coverage by 1 cm²: W = 25.0 × 10⁻⁷ J
• Area change: ΔA = 1 cm² = 1 × 10⁻⁴ m²
• Surface tension of pure water: γ_water = 0.072 N/m

Relationship between work and surface tension:

When a film is removed from the surface, work is done against surface tension. The work done is:

$ $

Answer: 0.047 N/m

$ \text{Explanation of Physisorption}$

Physisorption (or Physical Adsorption) is a type of adsorption where the gas molecules (adsorbate) are held to the surface of the solid (adsorbent) by weak intermolecular forces.

The primary force responsible for this weak interaction is the van der Waals force.

Van der Waals forces include London dispersion forces, dipole-dipole interactions, and dipole-induced dipole interactions. These are general, non-specific forces that exist between all atoms and molecules.

• (A) This assumption is correct. Langmuir adsorption model assumes that adsorption occurs in a single monolayer, meaning only one molecule adsorbs at each site.
• (B) This is also correct. Langmuir model assumes that all adsorption sites are identical and have the same energy of adsorption.
• (C) This assumption is incorrect. Langmuir adsorption model assumes that adsorption on one site does not affect adsorption on neighboring sites (no interaction between adsorbed molecules).
• (D) This is correct. At equilibrium, the rate of adsorption equals the rate of desorption in the Langmuir adsorption model.

Thus, the correct answers are (A), (B), and (D)