Chemistry I Honors

Kinetics

What is Kinetics?

• This is a totally different study than anything we have done.

• Some of it uses concepts from Unit 1, but the main focus of the topic is new.

• Kinetics is the study of the rate of a reaction.

• There is no worry as to whether the reaction will occur – it is assumed that a reaction does happen.

• Instead, we focus on how fast the reactants are consumed.

From Unit #1

Exothermic Reaction Endothermic Reaction

The Boltzman Distribution

Kinetics Factor #1

• Part of the study of Kinetics will focus on variables that change the rate at which the reaction occurs. The most common variable is the temperature.

• Remember that the velocity and energy of the particles in a system changes directly with the temperature.

• As the temperature increases, the energy of the particles increases.

• Question is – what does this do to the Boltzman distribution?

Changing the Temperature

Kinetics Factor #2

• The 2nd factor considered is the presence of a catalyst.

• We learned in Unit 1 that a catalyst speeds up a reaction.

• The graph on the right shows what a catalyst does to the exothermic graph.

Catalyst and the Boltzman Distribution

Kinetics Factor #3

• The final kinetics factor is the concentration of the reactant particles.

• Think of this simply as the number of available molecules to react.

Consider Dodgeball

Dodgeball Kinetics

• At the beginning of the game, there are lots of reactant “people” and the rate at which they are eliminated (reacted) is high.

• High concentration of reactant particles results in higher rate of reaction.

• But as the number of reactant “people” decreases, there are fewer collisions – the rate of reaction goes down.

• Lower concentration of reactant particles results in lower rate of reaction.