CHEM 156 Study Guide - Comprehensive Final Exam Guide - Amplitude Modulation, Page 3, Polymerization
Document Summary
Part of gas/ vapor phase remained attached to the solid surface. Physisorption (physical adsorption): weak vanderwaals attraction btwn adsorbate and solid surface. Characterization of porous materials allows determination of specific surface area, pore size distribution and pore volume. Low heats of adsorption, no violent or disruptive structural changes. Can involve multiple layers of adsorbate, thus allowing for pore measurements. Adsprotion equilibrium is achieved quickly since no activation energy is generally required. Physical adsorption is fully reversible, allowing adsorbate to fully adsorv and desorb. Adsorption isotherms: obtained by measuring amount of gas adsorbed across wide range of relative pressures at constant temp. Desorption isotherms: measuring gas removed as pressure is reduced. Type 1 isotherm: pores typically microporous with exposed surface residing almost exclusively inside micropores, which once filled with adsorbate, leave little or no external surface for furthur adsorption. Type 2: most frequently found when adsorption occurs in nonporous powders or powders with diameters exceeding micropores.
