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rateofreactionsdjdjdkdmdmmrsjsks ppt.ppt
- 1.
- 2. Fast or SlowReactions • Extremely slow reactions – Iron rusting – Limestone weathering • Extremely fast reactions – Explosion
- 3. Measuring Rate of Reactions •Some rate of reactions have detectable change with respect to time • Changes that are observable like – When a volume of gas is given off – When there is a change in mass during the reaction – When there are temperature changes – When there are colour changes – When a precipitate forms – When there are pH changes
- 4. Collision Theory • Fora reaction to occur – The reacting particles must collide into each other – The reacting particles must possess enough activation energy • Once products are formed, effective collisions have occurred
- 5. Factors affecting Rate ofReactions • Temperature of the substances used (reactants) • Concentration of the substances used (reactants) • Pressure on the reaction • Particle size (surface area) of the substances used (reactants) • Presence of catalyst
- 6. Temperature • Rate ofreaction increases with increasing temperature • High temperature, particles have greater heat energy • Particles move faster with greater kinetic energy • Leading to more collisions between particles • Increased probability of effective collision • Reactions take place faster • Speed of reaction doubles when the temperature rises by 10 C
- 7. Temperature Amt of productformed Time Higher temperature Lower temperature
- 8. Concentration • Rate ofreaction increases with increasing concentration • Higher concentration, more reacting particles are present • Greater probability of an effective collision • Faster rate of reaction
- 9. Concentration – Same no.of moles Amt of product formed Time/s Higher concentration Lower concentration
- 10. Concentration – Different no.of moles Amt of product formed Time/s Higher concentration Lower concentration
- 11. Pressure • Rate ofreaction increases with increasing pressure • Higher pressures, reacting particles are closer together • Increasing concentration per unit volume • Greater probability of an effective collision • Faster rate of reaction
- 12. Pressure Amt of productformed Time/s Higher pressure Lower pressure
- 13. Particle Size • Rateof reaction increases when particle size decreases • Smaller particles has greater surface area than larger particles of the same mass • Greater surface area for collision by another reacting particle • Greater probability of an effective collision • Faster rate of reaction
- 14. Particle size Amt ofproduct formed Time/s Smaller particle size Larger particle size
- 15. Catalyst • Presence ofcatalyst increases rate of reaction • (Presence of inhibitors decreases rate of reaction) • Catalysts lower activation energy of reactants • Aids the formation of unstable intermediate products • Increases probability of formation of products • Faster rate of reaction
- 16. Catalyst Amt of productformed Time/s Use of catalyst Absence of catalyst
- 17. Catalyst Energy Time/s Use of catalyst Absenceof catalyst Ea Ea
- 18. Catalyst Definition: A substancewhich increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy but remains unchanged at the end of the reaction