Rate of Reaction

Chemical reaction can be observed by

1. Volume of gas liberated (Laboratory Work 1.2, Experiment 1.1)
2. Pressure changes
3. Precipitate formation (Experiment 1.2)
4. Change in the concentration of a liquid reactant
5. Change in the pH value
6. Change in mass during the reaction
7. Colour changes / Change on the colour of intensity
8. Temperature changes (Experiment 1.3)

Rate of reaction is the measurement of the speed which reactants are converted into products in a chemical reaction.
Average rate of reaction is the average value of the rate of reaction over an interval of time.

Instantaneous rate of reaction / Rate of reaction at a given time are the actual rate of reaction at that instant.
Factors Affecting the Rate of Reaction

1. Total surface area of solid reactant
2. Concentration of reactant
3. Temperature of reactant
4. Use of catalyst
5. Pressure of gaseous reactant

Effect of total surface area of solid reactant on the rate of reaction

1. Smaller the size (increase the total surface area), cm³, of the solid reactant, the higher the rate of reaction, cm³ s^-1 or cm³ min^-1.

Effect of concentration of a liquid reactant on the rate of reaction

1. Higher the concentration, mol dm^-3, of a liquid reactant, the higher the rate of reaction, mol dm^-3 s^-1 or mol dm^-3 min^-1.

Effect of temperature on the rate of reaction

1. Increase in temperature, the higher the rate of reaction.

Effect of catalyst on the rate of reaction

1. Alters the rate of reaction
2. It is specific in its action. It can only catalyse a particular reaction
3. Does not change the quantity of products formed
4. Only small amount of catalyst is needed to increases the rate of reaction. (An increase in the quantity of catalyst will increase the rate of reaction but only a very slight increase.)
5. Catalyst remains chemically unchanged but may undergo physical changes.

Effect of pressure on the rate of reaction

1. Increase in pressure, the higher the rate of reaction (reversible reaction and gaseous reactants and gaseous product).

Collision Theory and Activation Energy
Collision theory states a reaction occur when the particle of the reactant collide with each other with the correct orientation and achieve activation energy.
Effective collision is the particles collide with the correct orientation and achieve activation energy which result in a reaction.
Ineffective collision is the particles that collide with energy less than activation energy or wrong orientation.
Activation energy, E_a, is the minimum kinetic energy that colliding particles of the reactants must possess. It can be visualised by energy profile diagram.