Q1(k). Physical and chemical adsorption

Answer in brief

Physisorption involves weak intermolecular forces; chemisorption involves surface chemical bonding and usually provides reactant activation in heterogeneous catalysis.

Key points

• Physisorption is relatively nonspecific, often reversible, can form multilayers and generally has smaller adsorption enthalpy. It typically requires little activation energy.
• Chemisorption is specific to adsorbate and surface, normally forms a monolayer, has larger bonding energies and may require activation. Strong binding can make desorption difficult.
• In heterogeneous catalysis, chemisorption commonly weakens reactant bonds and creates activated surface species that react before desorbing.