Chemical Kinetics

Vocabulary
1. Reaction rate- is the speed at which a chemical reaction occurs
2. Chemical Kinetics- is the area of chemistry concerned with the speeds, or rates, of reactions.
3. instantaneous rate- of a reaction, which is the rate at a particular instant during the reaction.
4. catalyst- is a substance that increases the rate of a reaction without undergoing a net chemical change itself
5. homogeneous catalyst- is one that is in the same phase as the reactants.
6. heterogeneous catalyst -has a different phase from the reactants
7. reaction mechanism -details the individual steps that occur in the course of a reaction.
8. unimolecular, bimolecular, or termolecular,- depending on whether one, two, or three reactant molecules are involved
Factors that affect reaction rates
1. 1- Physical state of the reactants. Reactants must come together to react. The more readily reactant molecules collide with one another, the more rapidly they react
2. 2- Reactant concentrations. Most chemical reactions proceed faster if the concentration of one or more reactants is increased.
3. 3- . Reaction temperature. Reaction rates generally increase as temperature is increased.
4. 4- The presence of a catalyst. Catalysts are agents that increase reaction rates without themselves being used up.
Reaction rates
1. The speed of an event is defined as the change that occurs in a given time interval, which means that whenever we talk about speed, we necessarily bring in the notion of time.
2. Similarly, the speed of a chemical reaction—its reaction rate—is the change in the concentration of reactants or products per unit of time.
Reaction Orders
1. The Exponents in the Rate Law The rate law for most reactions has the form Rate = k[reactant 1]m[reactant 2]n The exponents m and n are called reaction orders.
THE CHANGE OF CONCENTRATION WITH TIME
1. first order reactions
  1. n is one whose rate depends on the concentration of a single reactant raised to the first power
2. integrated rate law
  1. ln[A]t - ln[A]0 = -kt or ln [A]t [A]0 = -kt
3. differential rate law
  1. Rate = - [A]/t = k[A]
4. second order reactions
  1. rate depends either on a reactant concentration raised to the second power or on the concentrations of two reactants each raised to the first power.
5. half life
  1. Half-life is a convenient way to describe how fast a reaction occurs, especially if it is a first-order process. A fast reaction has a short half-life

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Chemical Kinetics

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	Created by rodrigo sala about 10 years ago