9701 · 8.3
Homogeneous and heterogeneous catalysts
Catalysts are chemical matchmakers that speed up reactions by providing an easier route, without getting used up themselves. They come in two main types: homogeneous (in the same state as reactants) and heterogeneous (in a different state).
Need to know
What you need to know
- A catalyst provides an alternative reaction route with a lower activation energy ($E_a$).
- It is not used up in the overall reaction; it is regenerated.
- It does not affect the enthalpy change ($\Delta H$) of the reaction.
- It does not change the position of equilibrium but allows it to be reached more quickly.
Explanation
Catalysts: The Reaction Accelerators
- A catalyst provides an alternative reaction pathway with a lower activation energy ($E_a$), increasing the reaction rate. It is not consumed in the overall reaction.
- In homogeneous catalysis, the catalyst is in the same physical state (phase) as the reactants, often forming an intermediate species.
- In heterogeneous catalysis, the catalyst is in a different phase from the reactants. The reaction occurs on the catalyst's surface via adsorption.
- A catalyst does not change the overall enthalpy change ($\Delta H$) or the position of equilibrium ($K_c$). It increases the rate of both the forward and reverse reactions equally.