10.2 - Catalysts Flashcards
What does a catalyst do?
A catalyst is a substance that changes the rate of a chemical reaction without undergoing any permanent change itself
What can happen to a catalyst during a reaction?
A catalyst may react with a reactant to form an intermediate or may provide on which the reaction can take place.
At the end of the reaction the catalyst is regenerated.
How does a catalyst increase the rate of a chemical reaction?
A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway of lower activation energy.
What is a homogeneous catalyst?
A homogeneous catalyst has the same physical state as the reactants. The catalyst reacts with the reactants to form an intermediate. The intermediate then breaks down to give the product and regenerates the catalyst e.g. in ozone depletion.
What is a heterogeneous catalyst?
A heterogeneous catalyst has a different physical state from the reactants. Heterogeneous catalysts are usually solids in contact with gaseous reactants or reactants in solution. Reactant molecules are absorbed (weakly bonded) onto the surface of the catalyst, where the reaction takes place. After reaction, the product molecules leave the surface of the catalyst by desorption. e.g. Fe (s) in the Haber process.
