11.3 - Rate Factors & Collision Theory

Catalysts

• A catalyst is a substance that speeds up a chemical reaction without being used up in the process.
• It remains chemically unchanged, so its mass is the same at the start and end of the reaction.
• A catalyst doesn't appear in the balanced equation for the reaction.
• Enzymes are biological catalysts.

How a catalyst works

• A catalyst provides an alternative reaction pathway with a lower activation energy.
• A greater proportion of colliding particles have enough energy to react, so there are more successful collisions per second.

Catalysts in industry

• Catalysts allow reactions to run at lower temperatures and pressures.
• This reduces energy costs and burns less fossil fuel, making processes cheaper and more sustainable.

Example - Decomposing hydrogen peroxide

Hydrogen peroxide decomposes very slowly on its own. Adding solid manganese(IV) oxide speeds up the reaction:

hydrogen peroxide → water + oxygen

2H₂O₂(aq) → 2H₂O(l) + O₂(g)