DM.2 Flashcards
Catalytic activity
What are catalysts?
Catalysts are substances that speed up the rate of reactions without being used up in the process, by providing an alternative reaction pathway with a lower activation enthalpy.
What chemical property of transition metals make they good catalysts?
The availability of 3d and 4s electrons and their ability to change oxidation states.
What is heterogeneous catalysis?
This is when the catalyst is in a different phase/physical state from the reactants.
For heterogeneous catalysis with transition metals, what phase is the catalyst typically in and what phases are reactants in?
The transition metal catalysts are normally solid, and the reactants being in liquid or gas phase.
What happens in a heterogeneous catalysis with a transition metal catalyst?
The transition metal atoms on the surface can use its 3d and 4s electrons to form weak bonds with the reactants. Once the reaction has occurred on the surface, these bonds will break and products are released.
What is chemisorption?
It is a kind of adsortion when chemical bonds are formed between the catalyst surface and reactant.
What is homogeneous catalysis?
This is when the catalyst is in the same phase/physical state as the reactants.
For homogeneous catalysis with transition metals, what phases does the reaction normally take place in?
Both the transition metal catalyst and reactants are in aqueous phase.
What happens in a homogeneous catalysis with a transition metal ion catalyst?
The transition metal ion forms an intermediate compound with one or more of the reactants, which then breaks down to give the products.
Why are transition metal ions particularly effective catalysts for redox reactions?
This is because move readily from one oxidation state to another, acting as both oxidising and reducing agents. This oxidation state change can normally be observe as colour changes.
