Catalysts and measuring rate
Introduced| English | Meaning |
|---|---|
| catalyst/ˈkætəlɪst/ | A substance that increases a reaction rate without being used up overall. |
| enzymes/ˈenzaɪmz/ | Biological catalysts that increase reaction rates without being used up overall. |
| Haber process/ˈheɪbə ˈprəʊses/ | The industrial production of ammonia by reacting nitrogen with hydrogen under controlled temperature and pressure using a catalyst. |
Speeding reactions without using anything up
- Some substances make a reaction go faster yet are not used up themselves.
- These are catalysts 催化剂, and they work by lowering the activation energy.
A catalyst speeds up a reaction by:
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A lower Ea means more successful collisions.
After the reaction, a catalyst is:
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Catalysts are regenerated and reused.
A catalyst provides a pathway with a lower ______ energy.
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Lower Ea lets more collisions succeed.
How catalysts work
- A catalyst speeds up a reaction by providing a pathway with a lower activation energy.
- It is not used up, so a small amount can be reused again and again.
A catalyst lowers the activation-energy hill, so more collisions succeed and the reaction speeds up.
Catalysts & measuring rate
conc = c₀·bᵗ
A catalyst speeds the fall in concentration.
Biological catalysts found in living things are called:
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Enzymes are biological catalysts.
Catalysts in action
- Enzymes 酶 are biological catalysts in living things.
- Industry uses catalysts (e.g. iron in the Haber process 哈伯法) to speed reactions and save energy.
A gas syringe measures the volume of gas given off at regular times
A steeper gradient on a rate graph means a faster reaction.
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Gradient measures rate.
Measuring rate
- Rate can be found from the gradient of a graph (e.g. gas volume vs time).
- A steeper gradient means a faster rate; the line flattens when the reaction finishes.
A catalyst is not used up. It takes part in the reaction but is regenerated, so the same catalyst keeps working. That's why only a small amount is needed.
You've got it
- a catalyst speeds up a reaction by lowering the activation energy
- it is not used up, so a little is reused many times
- enzymes are biological catalysts; rate = the gradient of a rate graph