����ý

The rate of a reaction can be increased by adding a suitable catalyst. A catalyst is a substance which increases the rate of a chemical reaction but it is not used up (remains chemically unchanged at the end). It provides an alternative reaction pathway of lower activation energy.

Only a very small amount of catalyst is needed to increase the rate of reaction between large amounts of reactants.

A catalyst is specific to a particular reaction:

• different catalysts catalyse different reactions
• not all reactions have suitable catalysts

Activation energy

Activation energy is the minimum energy needed for a reaction to occur when two particles collide. It can be represented on an energy level diagram.

The diagram shows that a catalyst provided a reaction pathway of lower activation energy. This makes more of the collisions successful at a given temperature.

Prescribed Practical C6 - Investigate how changing a variable changes the rate of reaction