Catalytic Activity Flashcards
What is a catalyst ?
A substance that speeds up the rate of reaction but is itself unchanged or reformed at the end of the reaction
How do catalysts work ?
they provide an alternate route for the reaction to happen that has a lower activation energy.
why can transition metals act as catalysts ?
they can change their oxidation state by gaining or losing electrons within their d orbitals
The partially filled d orbitals can be used to form weak chemical bonds with the reactants which absorb onto the surface
This weakens the bonds in the reactants and holds the reactants close together on the metal surface
How can the efficiency of a catalyst be increased to decrease cost ?
Increasing the surface are
Use of an inert support medium- catalyst is spread on to or impregnated into a support medium. This increases the surface to mass ratio and reduces the amount needed.
purifying the reactants to minimise poisoning of the catalyst
What is an example of an inert support medium ?
a catalytic converter
How does purifying the reactants minmise poisoning of the catalyst ?
impurities block active sites
What are heterogenous catalysts ?
catalysts which are in a different phase to the reactants
What are homogenous catalysts ?
Catalysts which are in the same phase as the reactants
Why might an uncatalysed reaction with two negatively charged ions reacting together have a high activation energy ?
the negative ions repel eachother
What is Autocatalysis ?
when the products from a reaction is a catalyst for the reaction
What are features of a reaction that has Autocatalysis ?
the reaction rate is initially slow (no catalyst has been formed)
As the concentration of the catalyst product increases, the rate will also increase
