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
Surface Area of Solid ReactantRate 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
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.
TemperatureWhen temperature increases rate of reaction increases. At high temperatures fraction ofmolecules having energy greater than activation energy increases.
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
Effect of LightGreater the intensity of light greater is the speed of some reactions. Light contains photons which have sufficient energy to overcome activation energy.
Examples of Photochemical reactions• PhotosynthesisC6H12O6 +6 O2 6 CO2 + 6 H2OPhotography2 AgBrsunlight2 Ag + Br22 Br-Br2 + 2 electronsAg+ + electron Ag (basis of photography)