reaction rates and equilibrium 10.2- Catalysts Flashcards
(8 cards)
what is a catalyst?
a substance that changes the rate of a chemical reaction without undergoing any permanent change itself.
what are 3 features of catalysts?
-are not used up in the reaction
-may react with a reactant to form an intermediate, or may provide a surface on which the reaction can take place.
-at the end of the reaction, the catalyst is regenerated.
How does a catalyst increase rate of reaction?
provides an alternative pathway of lower activation energy.
What is a homogenous catalyst?
has the SAME physical state as the reactants.
How do homogenous catalysts work?
It reacts with the reactants to form an intermediate. The intermediate then breaks down to give the product and regenerates the catalyst.
e.g. making esters with sulfuric acid as a catalyst.
e.g. ozone depletion (Cl. as catalyst)
What is a heterogenous catalyst?
Has a DIFFERENT physical state from the reactants. They are usually solids in contact with gaseous reactants or reactants in a solution.
How does a heterogenous catalyst work?
Reactant molecules are absorbed (weakly bonded) onto the surface of the catalyst where the reaction takes place. After the reaction, the product molecules leave the surface of the catalyst by desorption.
e.g. making ammonia (Haber process)
e.g. hydrogenation of alkenes.
How are catalysts economical?
They increase rate of reaction by lowering activation energy.
This then reduces the temperature needed for the process and the energy requirements.
This means less electricity or fossil fuel is used. This can cut costs and increase profitability. These outweigh any costs associated with developing a catalytic process.
-sustainability requires industry to have high atom economy and fewer pollutants. Using less fossil fuels will cut emissions of CO2.
