3.2.2 reaction rates

Reactions can only occur when collisions take place between particles that have enough energy Energy is needed to break the relevant bonds in reactant molecules Minimum energy is activation energy

Minimum energy which particles need to collide to start a reaction

There are more particles per unit volume so the particles collide with a greater frequency Higher frequency of effective collisions

Change in concentration of a substance in unit time Mol dm-3 s-1 Gradient = rate of reaction Initial rate = rate at the start of the reaction where it is fastest Draw a tangent

Increase reaction rates without getting used up Do this by providing alternative route with a lower activation energy so more molecules have energy above activation energy

In a different phase from the reactants Usually solids whereas reactants are gaseous or in solution Reaction occurs at surface of the catalyst

Same phase at the reactants Reaction proceeds through intermediate species

Speed up the rate of reaction - lower temperatures and pressures may be used Saves energy costs > fewer co2 emissions from burning of fossil fuels Less waste products

Connect gas syringe to tube going into conical flask