Rates of reaction

Variables that affect reaction rate

• Temperature

• Concentration

• presence of a catalyst

• surface area

• pressure

What has to happen for stimulated particles to react

1. The reacting particles have to collide

2. They have to have activation energy(E_a) to have a successful collision

Collision theory

High Temperature

• More collisions per second

  • The particles move faster therefore there are more collisions

  • High temp—> particles have more energy—> particles move faster—> more frequent collisions

• More energy per particle

  • The average energy increases

  • High temp—> more energy—> more likely to have equal or greater energy than the E_a —> more frequent successful collisions

High surface area

• More collisions per second

  • More particles are able to be collided with

High concentration

• More collisions per second

  • There are more particles to collide with the other particles

  • High concentration—> more particles per unit of volume—> particles will travel shorter distances before colliding—>more frequent collisions

Catalyst

A substance used to increase the rate of reaction but is not used up in the reaction. it can often be recovered and reused

It does this by providing an alternate reaction pathway which requires less E_a.

As particles require less E_a to react the proportion of collisions that result in a successful reaction is higher.

More frequent successful collisions means a faster rate of reaction.