What is collision theory? A theory used to explain chemical reactions in terms

of:

I. Collisions between particles

II. Effective collisions

III. Activation energy

The collision theory state: A chemical reaction occurs when the reactant particles

collide with each other for bond breaking & bond formation

Not all collision result in a reaction to form the product

Effective collisions: A collisions which achieved a minimum energy and with the correct orientation

What is activation energy? The minimum amount of energy which a reactant

must have that can result a chemical reaction.

Tenaga minimum yang diperlukan oleh bahan tindak balasyang akan menghasilkan tindak balas

Energy profile diagram

Exothermic reaction Endothermic reaction

Frequency of effective collision The number of effective collisions occuring in one

second

Frequency of effective collision

High

High rate of reaction

Low

Low rate of reaction

Collision Theory and Factors Affecting the

Rate of Reactions

Effect of Total Surface Area When size of reactant smaller, the total surface

area exposed to collision with other reactants is

bigger.

Thus, the frequency of collision increase.

Frequency of effective collision increase.

Hence, rate of reaction high.

Effect of Total Surface Area When size of calcium carbonate smaller, the

total surface area exposed to collision with other

reactants is bigger.

Thus, the frequency of collision between hydrogen ions and carbonate ions increase.

Frequency of effective collision between hydrogen ions and carbonate ions increase.

Hence, rate of reaction high.

Effect of Concentration & Pressure When concentration of solution increase, the

number of particles per unit volume of the

reactant increase.

Thus, the frequency of collision increase.

Frequency of effective collision increase.

Hence, rate of reaction high.

Effect of Concentration & Pressure When concentration of sodium thiosulphate

solution increase, the number of thiosulphateions per unit volume increase.

Thus, the frequency of collision between thiosulphate ions and hydrogen ions increase.

Frequency of effective collision between thiosulphate ions and hydrogen ions increase.

Hence, rate of reaction high.

Effect of Temperature When temperature increase, the kinetic energy

of the reactant increase.

Thus, frequency of collision increase.

Frequency of effective collision increase.

Hence, rate of reaction high.

Effect of Temperature When temperature increase, the kinetic energy

of the thiosulphate ion increase.

Thus, frequency of collision between thiosulphate ions and hydrogen ions increase.

Frequency of effective collision between thiosulphate ions and hydrogen ions increase.

Hence, rate of reaction high.

Effect of Catalyst The presence of catalyst allows the reaction to take

place through alternative path which requires a

lower activation energy.

Thus, colliding particles able to achieve the lower activation energy.

Frequency of effective collision increase.

Hence, rate of reaction high.

Effect of Catalyst The presence of copper(II) sulphate lower the

activation energy.

Thus, frequency of collision between zinc atom and hydrogen ions increase.

Frequency of effective collision between zinc atom and hydrogen ions increase.

Hence, rate of reaction high.

Ea

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