Catalysts
| English | Chinese | Pinyin |
|---|---|---|
| catalyst | 催化剂 | cuī huà jì |
| reaction mechanism | 反应机理 | fǎn yìng jī lǐ |
| homogeneous catalyst | 均相催化剂 | jūn xiāng cuī huà jì |
| heterogeneous catalyst | 多相催化剂 | duō xiāng cuī huà jì |
A shortcut for reactions
- A catalyst 催化剂 speeds up a reaction but is not used up.
- It works by giving a new route with a lower activation energy.
- It does not change the enthalpy of the reaction.
A catalyst speeds up a reaction by:
A catalyst offers a new mechanism with a lower Eₐ, so more molecules can react; it is not used up.
A catalyst speeds up a reaction by providing a route with a lower activation energy.
It is not used up.
How a catalyst works
- A catalyst provides a different reaction mechanism 反应机理 with a lower $E_A$.
- On the Boltzmann distribution, lowering $E_A$ moves the line left, so more molecules can react → more effective collisions → faster rate.
- The enthalpy change $\Delta H$ is unchanged — only the activation energy is lowered.
A catalyst gives a route with lower activation energy; the enthalpy change is unchanged
Catalysts
a catalyst lowers Ea
A catalyst lowers Ea, so a bigger fraction of molecules can react — without heating.
A catalyst does NOT change the:
A catalyst lowers Eₐ and speeds the rate, but the overall ΔH (reactants to products) is unchanged.
Match each catalyst idea to its meaning.
Each item links the term to its correct meaning.
Two types
- a homogeneous catalyst 均相催化剂 is in the same physical state as the reactants (e.g. an acid dissolved among liquids).
- a heterogeneous catalyst 多相催化剂 is in a different state (e.g. solid iron speeding up the gases in the Haber process; a car's catalytic converter).
A homogeneous catalyst mixes in with the reactants; a heterogeneous one is a separate surface
A heterogeneous catalyst is one that is:
Heterogeneous = different state (e.g. solid catalyst, gas reactants); homogeneous = same state.
Solid iron speeding up the gas reaction in the Haber process is an example of a:
The solid iron is in a different state from the gaseous reactants, so it is a heterogeneous catalyst.
How a catalyst changes the picture
- A catalyst gives an alternative pathway with a lower activation energy.
- More molecules now have enough energy to react, so the rate rises — without being used up.
You've got it
- a catalyst speeds up a reaction, is not used up, and gives a route with lower $E_A$
- lower $E_A$ → more molecules can react → faster rate; $\Delta H$ is unchanged
- homogeneous = same state as reactants; heterogeneous = different state (e.g. solid iron, catalytic converter)