5.3- CATALYSTS Flashcards
What are catalysts?
substances that affect rate of chemical reactions without being chemically changed themselves at end of reaction
What are catalysts usually used for?
used to speed up reactions so they’re important in industry
Why is it cheaper to use a catalyst than using high temps + pressures?
catalysts not used up
Why do catalysts work?
they provide different pathway for reaction, one with lower activation energy
What do catalysts reduce?
activation energy of reaction
Do catalysts affect the enthalpy change of a reaction?
no
Do catalysts affect the position of equilibrium in a reversible reaction?
no
What are all new petrol-engine cars now equipped with?
catalytic converters in their exhaust systems
What do catalytic converters in the exhaust systems of petrol-engine cars do?
reduce levels of number of polluting gases
What is the catalytic converter?
honeycomb, made of ceramic material coated with platinum + rhodium metals- catalysts
What does the honeycomb shape of catalytic converters provide?
enormous SA, on which reactions take place, so little of these expensive metals goes a long way
Reactions for the polluting gases forming less harmful products from catalytic converters? (2)
carbon monoxide + nitrogen oxides -> nitrogen + carbon dioxide
hydrocarbons + nitrogen oxides -> nitrogen + carbon dioxide + water
Where does the reactions for the catalytic converter happen?
on surface of catalyst
What is the first process for the catalytic convert reactions?
adsorption
What is adsorption (first step of catalytic convert reactions)?
gases first form weak bonds with metal atoms of catalyst
