This document discusses 5 key factors that affect the rate of chemical reactions: 1. The surface area of solid reactants - increasing the surface area by powdering increases the rate. 2. The concentration of reactants - higher concentrations increase the number of collisions and thus the rate. 3. The temperature - higher temperatures provide more energy to overcome the activation energy barrier. 4. The presence of catalysts - catalysts lower the activation energy and increase the rate. 5. Exposure to light - light provides photons that can supply the energy needed to initiate photochemical reactions.

1. Objective:To Understand the factors
affecting the rate of reaction
Factors affecting the rate of reaction
are
1. Surface area of any solid reactant
2. Concentration of reactant
3. Temperature
4. Catalyst
5. Influence of light in some reaction

2. Surface Area of Solid Reactant
Rate of reaction faster when the sample is
powered
A solid has large surface area when
powered than when it is in larger pieces.
Mixed powders will be in greater contact
with each other and are more likely to
react

3. Concentration
• Rate of reaction increases when the
concentration of reactant increases.
• According to collision theory rate is
proportional to number of effective collisions
between the reactant molecules .
• If concentration increases number of effective
collisions increases and rate increases.

4. Temperature
When temperature increases rate of
reaction increases.
At high temperatures fraction of
molecules having energy greater than
activation energy increases.

5. Catalyst
• A substance that increases the rate of a
reaction without being consumed in the
reaction .
• It increases the rate by lowering the activation
energy of the reaction.
• Examples : Iron – Haber process
• Manganese Dioxide –
Decomposition of Hydrogen Peroxide

7. Effect of Light
Greater the intensity of light greater
is the speed of some reactions.
Light contains photons which have
sufficient energy to overcome
activation energy.

8. Examples of Photochemical reactions
• Photosynthesis
C6H12O6 +6 O2 6 CO2 + 6 H2O
Photography
2 AgBrsunlight2 Ag + Br2
2 Br-Br2 + 2 electrons
Ag+ + electron Ag (basis of photography)