CHEMICAL KINETICS

Chemical Kinetics

It is the study of reaction rates and mechanism

Reaction Rate

It is the change in concentration of reactants or products per unit time. Its unit is molar per second or M/s

Rate Law

It is an expression which relates that rate of a reaction to the rate constant and the concentrations of the reactants.

Reaction Order

The order of a reaction is important in that it enables us to classify specific chemical reactions easily and efficiently.

Zero Order

the rate is independent of the concentration so rate is equal to rate constant

First Order

the rate is dependent on the concentration

Second Order

the rate is dependent on the square of the concentration

Half life of Chemical Reaction

It is the time it takes for the concentration of a reactant to decrease to half of its initial value

For first order

the half-life is constant and independent of the initial concentration

For other orders

the half-life depends on the initial concentration

Transition state theory

it also known as activated complex theory, explains reaction rates by proposing that reactions proceed through a short-lived, unstable intermediate state

Transition state

It is a configuration where the potential energy of the system is at a maximum along the reaction pathway. It’s a fleeting, unstable structure that exists for a very short time, transitioning either back to the reactants or on to the products

Molecularity of chemical reaction

It is the number of molecules or ions that participate in the rate determining step

Unimolecular

a single species makes up the transition state

Bimolecular

two reacting species combine in the transition state of the rate-determining step

Termolecular

relatively improbable case of three independent specifies coming together in the transition state

Collision theory

It states that the rate of a chemical reaction is determine by the frequency of collisions between reactant molecules

Collision frequency

The more often reactant molecules collide, the faster the reaction rate

Collision energy

The collision must have enough energy to break the bonds in the reactants and form new bonds in the products. This energy is called the activation energy

Collision orientation

The colliding molecules must be in the correct orientation to form new bonds

Activation energy

The minimum energy required to bring about a chemical reaction

Activation energy

Molecules must collide in order to react. In order to effectively initiate a reaction, collisions must be sufficiently energetic (kinetic energy) to break chemical bonds

Effect of temperature

High temperatures mean more particles have enough energy to overcome the activation energy barrier, leading to a faster reaction rate

Effect of temperature

increases the average kinetic energy of the molecules, which increases the number of collisions with enough energy to react

Effect of concentration

increases the rate of a chemical reaction because more reactant particles in a given space lead to more frequent collisions, which in turn increase the chance of successful reactions

Effect of surface area

increases the rate of a chemical reaction because more particles are exposed, leading to more frequent and successful collisions

Effects of pressure

increases the reaction rate because it forces gas molecules closer together, leading to more frequent and effective collisions

Effect of catalyst

increases the rate of chemical reaction without being consumed itself, by providing an alternative reaction pathway with a lower activation energy