5. catalysts Flashcards
definition
catalyst
a catalyst increases the rate of reaction by providing an alternative reaction pathway with a lower activation energy
the catalyst is chemically unchanged at the end of the reaction
do catalysts take part in reactions?
yes
but they are remade at the end
what catalyst is used in the Haber process to make ammonia
iron
Fe(s)
equation for the haber process
N2(g) + 3H2(g) 2NH3(g)
when you add a catalyst, why do more particles react in a given time
activation energy lowered
more particles with enough energy to react (when they collide)
what is a heterogeneous catalyst
a catalyst which is in a different phase from the reactants (different physical state s, l, g, aq)
e.g. of a heterogeneous catalyst
Fe(s) in Haber process. reactants N2(g) and H2(g) passed over the Fe(s) catalyst
why does increasing the surface are of the heterogenous catalyst e.g. Fe(s) in the Haber process increase the rate of reaction
reaction happens on the surface of the heterogeneous catalyst.
increasing SA of catalyst =
increased number of molecules that can react at the same time =
increased rate of reaction.
what is a homogenous catalyst
a catalyst which is in the same physical state as the reactants
(usually aq)
how does a homogeneous catalyst work
by forming intermediate species…
- reactant combines with catalyst to form intermediate species
- then reacts to form products and reform catalyst
why is the use of the catalyst Fe(s) in the haber process good for industry
without catalyst temperature would have to be raised to make reaction happen quick enough.
costs more and reduces amount of ammonia produced
what can a catalyst do to the properties of a product
make them more useful
e.g. of how catalyst changes the properties of a product to make them more useful
polyethene
without catalyst- less dense, less rigid
with catalyst - more dense, more rigid, higher mpt
how are catalysts good for environmental sustainability
lower temp and pressure = energy saved = less CO2 released & fossil fuel reserves preserved
allow different reaction to be used with better atom economy = reduced waste
what are catalytic converters on cars made from
alloys of platinum, palladium and rhodium
