Catalysts Flashcards
(21 cards)
Define catalyst:
A catalyst increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy.
What happens to the catalyst at the end of the reaction?
It is chemically unchanged.
Does it matter which reaction a catalyst catalyses?
Yes, they are very selective and usually only catalyse one reaction.
Can catalysts be reused?
Yes
Is a large amount of catalyst required to speed up a reaction?
No, only a small amount is needed.
What can catalysts either be?
They can either be homogeneous or heterogeneous.
What is meant by a homogeneous catalyst?
This is a catalyst that is in the same physical state as the reactants.
How does a homogeneous catalyst work?
It forms an intermediate species. The reatants combine with the catalyst to make the intermediate species, which then reacts to form the products and reform the catalyst.
What is meant by a heterogeneous catalyst?
This is a catalyst that is in a different phase from the reactants.
Where does the reaction happen on a heterogeneous catalyst?
It happens on the surface of the catalyst.
What would happen if you increased the surface area of a heterogeneous catalyst?
More reactants could react at the same time so the rate of reaction increases.
What would happen if you increased the surface area of a homogeneous catalyst?
Nothing
What is used to increase the surface area of a heterogeneous catalyst?
A honeycomb structure.
What catalyst is used in ammonia production?
Iron
What else can a catalyst be used for?
It can be used to change the properties of a product to make it more useful.
What are the key properties of polyethene if made without a catalyst?
It is less dense and less rigid.
What are the key properties of polyethene when made with a catalyst?
It is more dense, more rigid and has a higher melting point.
What is saved as a result of using a catalyst?
Lower temperatures and pressures can be used which will reduce the amount of energy needed for the reaction, meaning that there is less of a reliance on fossil fuels.
Why is there less waste when a catalyst is used?
Catalysts allow a different reaction with a better atom economy.
What is the purpose of catalytic converters?
To reduce the amount of of pollution released into the atmosphere.
What are catalytic converters made from?
They are made from alloys of platinum, palladium and rhodium.
