10.2 Catalysts Flashcards
What is a catalyst?
Substance that changes rate of reaction without undergoing any permanent change itself
What does a catalyst do?
Not used up in a chemical reaction
May react with a reactant to form an intermediate or could provide a surface for the reaction to take place
At the end of the reaction, catalyst is regenerated
How do catalysts increase rate of chemical reaction?
Provide an alternative reaction pathway of lower activation energy
Enthalpy of products and reactants in an exothermic reaction
Reactants have greater energy than products
Enthalpy of reactants and products in an endothermic reaction
Products have greater enthalpy than the reactants
Types of catalysts
Homogeneous catalysts
Heterogeneous catalysts
What is a homogeneous catalyst?
It has the same physical state as the reactants
Catalyst reacts with reactants to form an intermediate
Intermediate breaks down to give product and regenerates the catalyst
Examples of homogeneous catalysts
Making esters with sulfuric acid (all are liquids)
Ozone depletion with Cl radicals as catalysts (gases)
What are heterogeneous catalysts?
It has a different physical state from the reactants
Usually solids in contact with gaseous reactants or reactants in solution.
What happens with heterogeneous catalysts?
Reactant molecules are adsorbed (weakly bonded) onto the surface of the catalyst, where reaction takes place
After reaction, the product molecules leave the surface of the catalyst by desorption
Common industrial processes using heterogeneous catalysts
Haber process
Reforming
Hydrogenation of alkenes
Contact process
Haber process catalyst
Fe (s)
Reforming catalysts
Pt (s)
Rh (s)
Hydrogenation of alkenes catalyst
Ni (s)
Contact process catalyst
V2O5 (s)
