logging in or signing up Reaction Rates Revision pwict Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 1778 Category: Education License: All Rights Reserved Like it (0) Dislike it (0) Added: August 12, 2008 This Presentation is Public Favorites: 0 Presentation Description For Year 12 Chemistry Students Comments Posting comment... By: cpj2 (26 month(s) ago) Gostaria de receber esse excelente material no seguinte email: cpj2@uol.com.br Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Rates of Reaction : Rates of Reaction Chapter 26 Measuring Rates of Reaction : Measuring Rates of Reaction No too interested in accurate timing More interested in comparisons Rates as rx proceeds? : Rates as rx proceeds? Many reactions tend to slow down Occurs as reactants get used up Factors Affecting Rx Rates : Factors Affecting Rx Rates Collision Theory Demolition Derby Illustration : Demolition Derby Illustration Rate of wipeouts depends on: How crowded the field is How fast the cars travel Size of the cars Strength of the cars Geometry of collisions (head-on or side-on etc) Demolition Derby Illustration : Demolition Derby Illustration Application to reactions: How crowded concentration Speed temperature Size surface area Strength stability of reactants Geometry accounts for randomness Explanations : Explanations Concentration – particles are closer and more likely to collide faster rx Temperature – faster – more collision impact faster rx Surface area – more chance of contact faster rx Strength & Geometry – can’t do much to change this – depends on the substances Activation Energy : Activation Energy Most rxs not spontaneous Usually require something to start Petrol – tiny spark Coal – roaring fire Provides an energy barrier for the rx Higher temp more particles have energy to overcome the energy barrier Distribution of particle energy : Distribution of particle energy Energy of particles (average speed) Number of particles (frequency) A B Normal distribution at 25oC Distribution of particle energy : Distribution of particle energy Energy of particles (average speed) Number of particles (frequency) A B Normal distribution at 55oC Activation Energy –Exothermic Rx : Activation Energy –Exothermic Rx Energy Reactants Products Before rx After rx Activation Energy H Activation Energy –Endothermic Rx : Activation Energy –Endothermic Rx Energy Reactants Products Before rx After rx ActivationEnergy H Activation complex : Activation complex Intermediate step – more energy Activation complex Eg. H2 + ½ O2 H2O First H2 and ½ O2 split into individual atoms Reaction Mechanisms : Reaction Mechanisms Single step rx – only 1 activation complex Many rxs involve multiple steps Substances formed after each step – intermediates Each step also has an activation complex with its own activation energy Multiple Step Rx : Multiple Step Rx Energy ActivationEnergy H Intermediates Activated complexes Rate determining step : Rate determining step Multi-step rx – step with highest activation energy slowest Rate determining step Catalysts : Catalysts Speeds up a rx by providing an alternate pathway with a lower activation energy Does not get used up in the rx – can be used again and again Small amount of catalyst can make a big difference Can speed up a rx by 108 to 1011 times Catalysts may be damaged physically Hurdles analogy : Hurdles analogy Uncatalysed pathway – few particles have enough energy to go over Catalysed pathway – most particles have enough energy to go over Catalysts : Catalysts Catalysts may be altered physicallyeg may melt, break into bits etc Catalysts may be poisoned – if a chemical attaches to it and prevents the catalysis Catalysis and the Haber process : Catalysis and the Haber process ½ N2 + 1½ H2 NH3 Very slow reaction Catalyst of iron and a mixture of other substances works best Requires a large surface area Depend on adsorbtion – sticking to surface Catalyst can last for 8 years Can be poisoned by H2S Enzymes : Enzymes p 439 Enzymes cf Catalysts : Enzymes cf Catalysts Enzymes - proteins “Biological catalysts? Specificity Mild conditions Denaturing Image from www-news.uchicago.edu/.../06/061011.ied.shtml Human insulin degrading enzyme How enzymes work : How enzymes work Substrate Active site Shape Specific Images from: www.chem4kids.com/files/bio_enzymes.html Catalysts in Everyday Life : Catalysts in Everyday Life Examples For polymerisation For hydrogenation For producing ammonia For reducing air pollution from cars Catalytic Converter : Catalytic Converter Catalytic Converter : Catalytic Converter The end : The end You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
Reaction Rates Revision pwict Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 1778 Category: Education License: All Rights Reserved Like it (0) Dislike it (0) Added: August 12, 2008 This Presentation is Public Favorites: 0 Presentation Description For Year 12 Chemistry Students Comments Posting comment... By: cpj2 (26 month(s) ago) Gostaria de receber esse excelente material no seguinte email: cpj2@uol.com.br Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Rates of Reaction : Rates of Reaction Chapter 26 Measuring Rates of Reaction : Measuring Rates of Reaction No too interested in accurate timing More interested in comparisons Rates as rx proceeds? : Rates as rx proceeds? Many reactions tend to slow down Occurs as reactants get used up Factors Affecting Rx Rates : Factors Affecting Rx Rates Collision Theory Demolition Derby Illustration : Demolition Derby Illustration Rate of wipeouts depends on: How crowded the field is How fast the cars travel Size of the cars Strength of the cars Geometry of collisions (head-on or side-on etc) Demolition Derby Illustration : Demolition Derby Illustration Application to reactions: How crowded concentration Speed temperature Size surface area Strength stability of reactants Geometry accounts for randomness Explanations : Explanations Concentration – particles are closer and more likely to collide faster rx Temperature – faster – more collision impact faster rx Surface area – more chance of contact faster rx Strength & Geometry – can’t do much to change this – depends on the substances Activation Energy : Activation Energy Most rxs not spontaneous Usually require something to start Petrol – tiny spark Coal – roaring fire Provides an energy barrier for the rx Higher temp more particles have energy to overcome the energy barrier Distribution of particle energy : Distribution of particle energy Energy of particles (average speed) Number of particles (frequency) A B Normal distribution at 25oC Distribution of particle energy : Distribution of particle energy Energy of particles (average speed) Number of particles (frequency) A B Normal distribution at 55oC Activation Energy –Exothermic Rx : Activation Energy –Exothermic Rx Energy Reactants Products Before rx After rx Activation Energy H Activation Energy –Endothermic Rx : Activation Energy –Endothermic Rx Energy Reactants Products Before rx After rx ActivationEnergy H Activation complex : Activation complex Intermediate step – more energy Activation complex Eg. H2 + ½ O2 H2O First H2 and ½ O2 split into individual atoms Reaction Mechanisms : Reaction Mechanisms Single step rx – only 1 activation complex Many rxs involve multiple steps Substances formed after each step – intermediates Each step also has an activation complex with its own activation energy Multiple Step Rx : Multiple Step Rx Energy ActivationEnergy H Intermediates Activated complexes Rate determining step : Rate determining step Multi-step rx – step with highest activation energy slowest Rate determining step Catalysts : Catalysts Speeds up a rx by providing an alternate pathway with a lower activation energy Does not get used up in the rx – can be used again and again Small amount of catalyst can make a big difference Can speed up a rx by 108 to 1011 times Catalysts may be damaged physically Hurdles analogy : Hurdles analogy Uncatalysed pathway – few particles have enough energy to go over Catalysed pathway – most particles have enough energy to go over Catalysts : Catalysts Catalysts may be altered physicallyeg may melt, break into bits etc Catalysts may be poisoned – if a chemical attaches to it and prevents the catalysis Catalysis and the Haber process : Catalysis and the Haber process ½ N2 + 1½ H2 NH3 Very slow reaction Catalyst of iron and a mixture of other substances works best Requires a large surface area Depend on adsorbtion – sticking to surface Catalyst can last for 8 years Can be poisoned by H2S Enzymes : Enzymes p 439 Enzymes cf Catalysts : Enzymes cf Catalysts Enzymes - proteins “Biological catalysts? Specificity Mild conditions Denaturing Image from www-news.uchicago.edu/.../06/061011.ied.shtml Human insulin degrading enzyme How enzymes work : How enzymes work Substrate Active site Shape Specific Images from: www.chem4kids.com/files/bio_enzymes.html Catalysts in Everyday Life : Catalysts in Everyday Life Examples For polymerisation For hydrogenation For producing ammonia For reducing air pollution from cars Catalytic Converter : Catalytic Converter Catalytic Converter : Catalytic Converter The end : The end