Catalysts Flashcards
What are catalysts?
Substances that increase the rate of reaction BY providing an alternative reaction pathway which has a lower Ea.
So a greater proportion of collisions result in reaction
Catalysts before and after a reaction
Unchanged and not used up
Are catalysts specific to one reaction?
Yes
2 types of catalyst
Homogeneous
Heterogeneous
Heterogeneous vs homogeneous catalysts
Homogeneous catalysts are the same state as reactants
Heterogeneous catalysts are different state as reactants
names of stages in heterogeneous catalysis
Adsorption
Reaction/ chemisorption
Desorption
Adsorption
Reactant molecules arrives at surface of catalyst and forms temporary bonds to it
Reaction/chemisorption
Bonds within reactant molecules are broken forming radicals
These then bond to form new products
Desorption
The temporary bond the product molecules had to catalyst is broken and the product molecule is released
Effect of a heterogeneous catalyst on energy profile diagram
The activation energy was lowered so lower peak
Homogeneous catalysts stages
-Reactants combine to form an intermediate species
-Then reformation of products and reformation of catalyst
Effect of homogeneous catalyst on energy profile diagram
Divides Ea into 2 humps: the stage for combining reactant and catalyst
The stage for formation of products and reformation of catalyst
How is the effect of catalysts shown on a maxwell-Boltzmann distribution?
Activation energy line is moved to left showing less energy
And therefore a larger area under graph shows more particles collide with sufficient energy to overcome Ea
Economic benefits of a catalyst
Lower production costs by lowering energy costs needed for a reaction
In a reversible reaction, by having a lower temp thanks to catalyst then more product in endothermic reaction is formed
