5.3 Flashcards
Define a catalyst (2)
(1) a substance that increases the RoR
(2) without being chemically changed
How do catalysts work? (2)
(1) They provide an alternative path for molecules to react
(2) this path has a lower Ea, which is why catalysts reduce the Ea
When a catalyst is added, how does the enthalpy diagram change? (2)
(1) the transition state
(2) is lower
Do catalysts affect the enthalpy change of reactions? (1)
No
Do catalysts affect the position of the equilibrium in a reversible reaction? (1)
No
Which catalyst is used for the Haber process? (1)
Iron
Which catalysts are used for the Ostwald process when making nitric acid? (2)
(1) rhodium
(2) platinum
Which catalyst is used for the hardening of fats with hydrogen? (1)
nickel
Which catalysts are used to crack hydrocarbon chains from crude oil? (3)
(1) aluminium oxide
(2) silicon dioxide
(3) zeolite
Which catalysts are used for catalytic converter reactions in car exhausts? (2)
(1) platinum
(2) rhodium
Which catalyst is used for esterification? (1)
H+ ions
What is the purpose of catalytic converters in cars? (1)
it reduces the levels of a number of polluting gases
Describe the structure & contents of catalytic converters? (3)
(1) honeycomb structure (provides high S.A.)
(2) made of ceramic
(3) coated with platinum & rhodium metals (catalysts)
How do catalytic converters work? (3)
(1) gases pass over the catalyst
(2) the polluting gases react with each other,
(3) forming less harmful products
Explain how reactions take place on catalysts. (5)
(1) Gases form weak bonds with the metal atoms of the catalyst - ADSORPTION
(2) This holds the gas molecules in just the right position for them to react together
(3) The gases then react on the surface
(4) The products break away from the metal atoms - DESORPTION
(5) This frees up room on the catalyst surface for more gases to take their place & react
During the reactions that take place on catalysts, why is the level of strength of the bonds that are between the catalyst & the gases very critical? (2)
(1) They must be strong enough to hold the gases for long enough to react
(2) but they also have to be weak enough to release the products easily
