Reaction Kinetics

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Slide 1

Chemical Kinetics

Slide 2

CA Standards

Slide 3

Collision Model

Collisions must have enough energy to produce the reaction (must equal or exceed the activation energy).

Reactants must have proper orientation to allow the formation of new bonds.

Slide 4

Activation Energy

The minimum energy required to transform reactants into the activated complex

(The minimum energy required to produce an effective collision)

Flame, spark, high temperature, radiation are all sources of activation energy

Slide 5

Exothermic Processes

Processes in which energy is released as it proceeds, and surroundings become warmer

Reactants  Products + energy

Slide 6

Endothermic Processes

Processes in which energy is absorbed as it proceeds, and surroundings become colder

Reactants + energy  Products

Slide 7

2NO2(g)  2NO(g) + O2(g)

Reaction Rates:

2. Can measure

appearance of

products

1. Can measure

disappearance of

reactants

3. Are proportional

stoichiometrically

Slide 8

The Reaction Mechanism

The reaction mechanism is the series of steps by which a chemical reaction occurs.

A chemical equation does not tell us how reactants become products; it is a summary of the overall process.

The  sign has represents the reaction mechanism, but gives no indication of the steps in the mechanism

Reactants  Products

Slide 9

The Rate-Determining Step

In a multi-step reaction, the slowest step is the rate-determining step. It therefore determines the rate of reaction.

Slide 10

Factors Affecting Rate

Temperature

Increasing temperature always increases the rate of a reaction.

Surface Area

Increasing surface area increases the rate of a reaction

Concentration

Increasing concentration USUALLY increases the rate of a reaction

Presence of Catalysts

Slide 11

Catalysis