A2 AQA Chem5 - Transition Metals: Heterogenous Catalysts | Homogeneous catlysts

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  • Created by: Jamila
  • Created on: 05-06-15 20:56
What is a catalyst?
A substance that speeds up the rate of a reaction by lowering the activation point whilst staying chemically unchanged.
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What is a heterogeneous catalyst?
A catalyst in a different phase as its reactants.
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What is a homogeneous catalyst?
A catalyst in the same phase as its reactants.
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What is a support medium?
It is a substance that is used to maximise the surface area of a heterogenous catalyst to increase the rate of reaction and minimise cost.
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What is Fe's role in the Harber process?
It is a heterogeneous catalyst in process making ammonia. Fe can be poisoned by sulpher impurities, when theybind to the Fe reducing surface area of Fe and rate of the haber process reaction.
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What us catalyst poisoning?
It is when impurities bind to the active site on the surface of the heterogeneous catalyst reducing the efficiency.
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Which hetererogeneoes catlysts and support medium are in a catalytic converter?
Pt, Pd and Rh on ceremic support shaped liek honeycomb which increases the surface area and reduces amount of catalyst needed,a as the metals are expensive. But can be poisoned by lead.
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What are catalytic converters?
They reduce the emmision of Co and No gasses by allowing them to react together to form CO2 and N2 which are less harmful. But they can be poisoned by lead.
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Which catalyst is used in the manufacture of methonal and what type of catalyst is it?
Cr2O3 us used in reaction between carbon monoxide and hydrogen. It is a heterogeneous catalyst.
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What is the contact process?
It is one of the stages in the manufacture of sulfuric acid.
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What makes transition metals good catalysts?
They can change their oxidation state as they have partially filled D orbitals so they can be catalysts.
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Which catalyst is used in the contact process?
V2O5 has variable oxidation state. It gets reduced into V2O4 and catalyses SO2 into SO3 then it gets oxiidised by oxygen back to V2O5.
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What homoegeneous catalyst is used during esterification?
Cocentrated sulfuric acid.
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what is the uncatalysed ereaction between Iodide and peroxodisulphate(VI) slow?
The two negative ions repel eachother to form I2 + 2SO42-
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What homogeneous catalyst is used to catalyse between Iodide and peroxodisulphate(VI)?
Fe2+ in a two step processwhere it makes the intermediate Fe3+.
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Which redox titration is autocatalysed by Mn2+.
In the redox titration between MnO4- and C2O42- mn2+ acts as a autcatalyist speeding up reaction between the two negative ions that repel each other.
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What is autocatalysis?
When the catalyst is a product in th reaction, and the reaction becomes self-catalysing.
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Why does the reaction between MnO4- and C2O42- eventually slow down?
When the MnO4- is used up the reaction eventually stops.
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What can be used to monitor the reaction between MnO4- and C2O42-?
MnO4- is purple and the products are colourless and the colorimeter does not interfere with the reaction as well as allows rapid determination of concentration.
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Active site of a heterogeneous catalyst?
The place where reactants are adsorbed and where the reaction takes place.
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Card 2

Front

What is a heterogeneous catalyst?

Back

A catalyst in a different phase as its reactants.

Card 3

Front

What is a homogeneous catalyst?

Back

Preview of the front of card 3

Card 4

Front

What is a support medium?

Back

Preview of the front of card 4

Card 5

Front

What is Fe's role in the Harber process?

Back

Preview of the front of card 5
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