Kinetics Collision Theory: How reactions takes place

Why are kinetics important? In order to control processes.  speed up useful reactions that occur to slowly  slow down reactions that are harmful Example:  Catalysts are used in our cars to rapidly convert toxic substances into safer substances  Refrigerators are used to slow the process of spoiling in food

Collision Theory How do reactions occur at the molecular level?  Molecules collide with each othercollide  Form activated complex Svante Arrhenius  Did some fancy math to figure out that number of collisions alone don’t account for reaction rates  He found that reactants also require: Activation energy (E a - energy to break bonds) AnimationAnimation Right orientation (Animation)Animation

What affects reaction rate? Temperature (Animation)Animation  Increased number of collisions  More molecules have enough activation energy  Remember Maxwell-Boltzmann distribution Increased temperature, distribution flattens out More molecules have Ea

What affects reaction rate? Higher concentration  Number of collisions increased Animation Animation 2 Increased surface area  Number of collisions increased  Animation Animation

What affects reaction rate? Catalysts  Def’n: substance that speeds up a rxn w/o being used up itself  Number of collisions with Ea increase Ea lowers Catalysts hold molecules in right orientation Homogeneous catalyst (same phase of matter)  Demo: Catalysis by Co 2+ (demo) Demodemo Heterogeneous catalyst (different phase) AnimationAnimation