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Catalysts for SQA Higher Chemistry
This page covers the following topics:
1. Reaction profile
2. Catalysts
3. Applications of catalysts
Another type of graph can be used when assessing rate of reaction. This graph shows the energy available in the reactant particles and indicates the proportion of them that have the required energy for a reaction.
A catalyst is a substance that lowers the activation energy of a reaction by providing an alternative pathway for reaction. The catalyst doesn't take part in the reaction so will not be altered or used up.
Catalysts are important to many industrial and biological reactions (inside plants or animals). Biological catalysts are given the name 'enzyme' and different enzymes are present in every cell of the human body to perform a number of vital reactions.
1
Look at this graph showing enzyme activity at different temperatures. Why does the rate of reaction fall at higher temperatures and not continue to increase?
At high temperatures the enzymes are deactivated as the structure of the proteins within them is altered (the proteins have been denatured).
2
What factor would result in more reactant particles being present in the reaction space?
Increasing pressure or concentration
3
What is the catalyst used in the Haber process? (the reaction between nitrogen and hydrogen to form ammonia)
Iron
4
How do catalysts affect rate of reaction using collision theory?
Catalysts increase rate of reaction as they lower Ea so more particles will have sufficient energy to react and there will be more frequent successful collisions.
5
What is the general mechanism of catalysis?
A transition metal will form a complex with the reagent undergoing oxidation or reduction to give or remove electrons as required. This elevates the reagent to a more reactive state so less energy is required for the reaction to take place.
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