2. What is chemical kinetics?
Chemical kinetics is the study of chemical reactions rates
Kinetics can be more simply described as how the
concentration of given reactant or product changes in time
during a chemical reaction
3. What is chemical kinetics?
In kinetics experiments, reaction conditions are changed in
a systematic way
The effect on the rate of the reaction (i.e. speed of
reaction) is measured
Reaction rates can be measured using a variety of
spectroscopic methods
4. Kinetics and mechanism
Kinetics provides a way to study complicate reactions and
determine how they proceed
Once we know how a reaction proceeds, we may able to
learn to control it
Kinetic studies can also provide evidence and support for
a theory about how a reaction works (its mechanism) but
never “Proved” the mechanism
5. Macroscopic Vs Microscopic
Aspects of kinetics
The microscopic aspect involves how fast the reaction
runs (overall)
Rate laws are determined by experiment
Rate laws shows the dependence on concentrations and/or
partial pressures of reactants
6. Macroscopic Vs Microscopic
Aspects of kinetics
The microscopic aspects of reactions involves how the
reaction proceeds at the molecular level
A reaction mechanism is determined, which includes a
series of elementary steps in converting reactants to
products
7. Kinetics and Mechanism
Example: SN1 Reaction
(H3C)C Br + H3C OH boil (H3C) O CH3
When t-butyl bromide is boiled in methanol, the reaction
produces methyl t-butyl ether
This looks like a very specific reaction, but it can be placed in a
large category of reactions called “First-Order”
8. Collision Theory and Reaction Rate
Collision theory affects the basic framework for
understanding chemical kinetics
The basic assumption is that molecules must be come into
contact (Collide) to react
Therefore, (forward) reaction rates are affected by several
factors
9. Factors Affecting Reaction Rates
1. Concentration of the reactant:
higher concentration leads to a faster rate
because there are more collisions
2.Temperature:
higher temperature leads to more collision and
with greater energy, which leads to a faster rate
10. Factors Affecting Reaction Rates
3. The Physical State of the reacants:
Molecules must mix to react (Solutions provide
more opportunites for mixing)
The amount of surface area on a solid available for
reaction
e.g. Nanoparticles have more surface area than
larger particles i.e. more surface area – faster rate
11. Factors Affecting Reaction Rates
The addition of catalyst:
Usually it involves different mechanism of
reaction
e.g. Enzymes, such as Trypsin, act as catalysts in
chemical reactions
