10.2 - Catalysts Flashcards
Define catalyst
A substance that changes the rate of a chemical reaction without undergoing any permanent change itself
What are 3 key things to remember about catalysts ?
- not used up in a chemical 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
Does a catalyst increase or decrease the rate of a chemical reaction ?
Increases the rate of a chemical reaction by providing an alternative reaction pathway of lower activation energy
Define homogeneous catalysts
Has the same physical state as the reactants
What are two examples of a reaction of gases and liquids that use homogeneous catalysts ?
- Making esters with sulfuric acid as a catalyst
- Ozone depletion
Define heterogenous catalysts
Has a different physical state from the reactants
What state are heterogeneous catalysts usually in ?
Solids
What happens when a heterogeneous catalyst comes 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
What are some examples of industrial processes that use heterogeneous catalysis ?
- making ammonia ( Haber process )
- reforming
- hydrogenation of alkenes
- making sulfur trioxide for sulfuric acid ( contact process )
Do catalysts increase the rate of industrial chemical reactions ?
Yes by lowering the activation energy
This then reduces the temperature needed for the process and the energy requirements
What is the economic advantage of reduced energy need in this process ?
If a chemical process requires less energy = less electricity or fossil fuel is used
Making the product faster and using less energy can cut costs and increase profitability
The economic advantage of using a catalyst outweigh any costs associated with developing a catalytic process
