reaction rates Flashcards
what is a catalyst
a substance that changes the rate of a reaction without undergoing any permanent change itself
how does a catalyst work
provides an alternative reaction pathway of lower activation energy, it may react with a reactant to form an intermediate or provide a surface on which the reaction can take place
what is a homogeneous catalyst
has same physical state as the reactants, reacting with the reactants to form an intermediate which then breaks down to give the product and regenerates the catalyst
what is a heterogeneous catalyst
has a different physical state from the reactants, usually solids in contact with gaseous reactants or reactants in solution
how does a heterogeneous catalyst work
molecules are absorbed onto the surface of the catalyst where the reaction takes place then the products leave by desorption
what happens on a boltzmann distribution curve as temperature increases
peak is lower and shifted to the right as a greater no of molecules can overcome the activation energy
what can be seen on a boltzmann distribution curve when a catalyst is used
a new activation energy is drawn (Ec) meaning a greater proportion of molecules exceeds the lower activation energy
what is dynamic equilibrium
rate of the forward reaction is equal to rate of reverse reaction and concs of reactants and products dont change
what is le chateliers principle
when a system in equilibrium is subject to an external change the system readjusts itself to minimise the effect of the change
if there are more products formed, has the position of equilibrium shifted to the left or right
right
