Reaction Kinetic : 11.3 Factor Affecting Reaction Rate

• There are 4 factors that affect the rate of reaction which are:
  • concentration
  • particle size
  • pressure
  • temperature

• Concentration
  • the relationship between the rate of reaction and the concentration can be show below:

   

• as concentration increase, the number of molecules per unit volume increase. 
• Therefore, the frequency of collision between the reactant molecules increase.
• the frequency of effective collision also increase hence increase the rate of reaction.

• Particle size
  • The relationship between the rate of reaction and the particle size can be show below:

  

• When the size of particles for the same masses of particles decrease, the total surface area of the particles increase
• The total surface area exposes for the collision increase, hence, the frequency of collision increase
• The frequency of effective collision also increase hence it increase the rate of reaction

• Pressure
  • Only applied for gaseous reactants
  • The relationship between the rate of reaction and pressure of the reactant can be show below:

  

• When the pressure increase, the volume of the reactant decrease.
• The reactant molecules become closer from each other, thus easier to collide
• Therefore, the frequency to collision increase and the frequency of effective collision also increase
• Hence, the rate of reaction increase

• Temperature
  • The relationship between the rate of reaction and temperature of the reactant can be show below :

  

• As the temperature increase, the average kinetic energy of the reactant particles increase
• Thus, it move faster and collide more often thus the frequency of collision increase

The frequency of effective collision also increase hence the rate of reaction increase

Reaction Kinetic : 11.2 Collision Theory and Transition State Theory

Ø Collision theory

-          Reaction is result from colliding particles with a certain frequency and minimum energy

-          The collision which produces a reaction is called effective collision

Ø Effective collision

         The collision which occur when the following condition is fulfilled:

-          Colliding molecules posses minimum energy which is equal or more than the activation energy

-          The reactants molecules collide at correct orientation

Ø Activation energy

         The minimum amount of energy required to initiate a chemical reaction

Ø Transition state

       Temporary state formed by reactant molecules as a result of collisions to form products.

       Characteristics of transition state :

-          Exist momentarity (temporary)

-          High-energy (potential energy higher than that of reactant and products

-          unstable

Reaction Kinetic : 11.1 Reaction Rate

• What is reaction rate?
  

• how fast the concentration of reactant(or product) are change in a chemical reaction
  

• How to expressing the reaction rate? 
  

                                              A + B 

                reaction rate = -d[A]/dt = d[B]/dt

• The negative value of [A] indicates the decreasing amount of A which is the reactant
  

• How to calculate the reaction rate ?
  

- by calculating the gradient of the following graph

• How to differential the rate of reaction?
  
  aA + bB → cC + dD
  

• rate equation for the above reaction can be written as:

   -1/a d[A]/dt = -1/b d[B]/dt = 1/c d[C]/dt = 1/d d[D]/dt

• Rate law and order of reaction