Q1(g). Why a finely powdered adsorbent works better

Answer in brief

Adsorption is a surface phenomenon. Powdering raises the surface area per gram enormously and exposes more active sites, so more gas or solute is adsorbed, and faster.

Key points

• Amount adsorbed per gram, x/m, is proportional to the specific surface area available.
• A 1 cm cube (6 cm²) cut into 1 µm cubes gives 10¹² cubes totalling 6 m², a 10⁴-fold increase; spheres: S = 6/(ρd).
• More surface atoms with unsatisfied valencies (residual forces); edges, corners, steps and defects are high-energy active sites.
• Porosity adds internal surface: activated charcoal 500 to 1500 m² g⁻¹, silica gel 500 to 800 m² g⁻¹.
• Rate also improves: shorter diffusion paths, so equilibrium is reached faster.