10.2 Catalysts
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What is a catalyst
A substance that changes the rate of a chemical reaction without undergoing any permanent change itself Catalyst is not used up in chemical reaction Catalyst may react with a reactant to form an intermediate or may provide a surface on which the reaction can take place At the end of the reaction, the catalyst is regenerated
A catalyst ______ the rate of a chemical reaction by providing an ______ reaction ______ of lower ______ energy.
Increases Alternative Pathway Activation
A homogeneous catalyst has the ______ physical state as the reactants. The catalyst reacts with the reactants to form an ______. The ______ then breaks down to give the product and ______ the catalyst.
Same Intermediate Intermediate Regenerates
Examples of reactions of gases and liquids that use homogenous catalysis
Making esters with sulfuric acid as a catalyst Ozone depletion (Cl• radicals as catalyst) 2O3(g) 3O2(g) The reactant and catalyst are both gases
A heterogeneous catalyst has a ______ physical state from the reactants. Heterogeneous catalysts are usually ______ in contact with ______ reactants or reactants in ______. Reactant molecules are ______ onto the surface of the catalyst where the reaction takes place. After the reaction, the product molecules leave the surface of the catalyst by ______.
Different Solids Gaseous Solution Absorbed Desorption
What do catalytic converters contain
A catalyst made of platinum, rhodium and palladium supported on a honeycomb mesh that provides a large surface area on which the reactions can take place.
How do catalytic converters work
Contain a catalyst made of platinum, rhodium and palladium on a honeycomb mesh to provide a large SA on which reactions can take place. Hot exhaust gases are passed over this heterogeneous catalyst, and harmful gases are converted into less harmful products.
What does combustion in a petrol engine form
The toxic gases carbon monoxide and nitrogen monoxide.
What does a catalytic converter convert carbon monoxide to
Oxidised to form carbon dioxide
What does a catalytic converter convert nitrogen monoxide
Reduced to nitrogen gas
What are any unburnt hydrocarbons oxidised to in a catalytic converter
Oxidised to water and carbon dioxide
It is estimated that 90% of all chemical materials are produced using…
…a catalyst
Catalysts increase the rate of many industrial chemical reactions by…
…lowering the activation energy. This then reduces the temperature needed for the process and the energy requirements
If a chemical process requires less energy, then less…
…energy or fossil fuel is used
What is the modern focus on sustainability
Requires industry to operate processes with high atom economies and fewer pollutants Using less fossil fuel will cut emissions of carbon dioxide
When is a chemical reaction said to have undergone autocatalysis
If a reaction product acts as a catalyst for that reaction Typically the reaction starts slowly and then speeds up as the products are formed
Example of autocatalysis
2MnO4- + 16H+ + 5C2O42- –> 2Mn2+ + 8H2O + 10CO2