Explain that catalysts lower Ea but don't change ΔH
Distinguish homogeneous vs heterogeneous catalysts
Understand enzymes as biological catalysts
Key Facts
• Catalyst provides alternative pathway with lower Ea
• Does NOT change ΔH (same reactants/products)
• Does NOT change equilibrium position
• Increases rate of BOTH forward and reverse
• Catalyst is regenerated (not consumed)
• Enzymes: lock-and-key or induced fit model
Tags
catalystactivation energyenzymeenergy diagram
Ea uncatalyzed (kJ/mol) 80
Ea catalyzed (kJ/mol) 40
ΔH rxn (kJ/mol) -50
Ea (no cat)
80
Ea (catalyzed)
40
ΔH
-50
Speedup (≈)
—
Catalyst types:
• Homogeneous: Same phase as reactants (e.g., H⁺ in ester hydrolysis)
• Heterogeneous: Different phase (e.g., Pt surface in catalytic converter)
• Enzyme: Biological protein catalyst (substrate fits active site)