cm4 - Reaction Rate How Fast Does the Reaction Go?...

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Reaction Rate How Fast Does the Reaction Go?
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Collision Theory In order to react molecules and atoms must touch each other. They must hit each other hard enough to react. Must break bonds Anything that increases how often and how hard will make the reaction faster.
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Energy Reaction coordinate Reactants Products
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Energy Reaction coordinate Reactants Products Activation Energy - Minimum energy to make the reaction happen – how hard
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Energy Reaction coordinate Reactants Products Activated Complex or Transition State
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Activation Energy Must be supplied to start the reaction Low activation energy Lots of collision are hard enough fast reaction High Activation energy Few collisions hard enough Slow reaction
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Activation energy If reaction is endothermic you must keep supplying heat If it is exothermic it releases energy That energy can be used to supply the activation energy to those that follow
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Energy Reaction coordinate Reactants Products Overall energy change
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Things that Affect Rate Temperature Higher temperature faster particles. More and harder collisions. Faster Reactions. Concentration More concentrated molecules closer together Collide more often. Faster reaction.
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Things that Affect Rate Particle size Molecules can only collide at the surface. Smaller particles bigger surface area. Smaller particles faster reaction. Smallest possible is molecules or ions. Dissolving speeds up reactions. Getting two solids to react with each other is slow.
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Things that Affect Rate Catalysts- substances that speed up a reaction without being used up.(enzyme). Speeds up reaction by giving the reaction a new path. The new path has a lower activation energy. More molecules have this energy. The reaction goes faster. Inhibitor- a substance that blocks a catalyst.
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Energy Reaction coordinate Reactants Products
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Pt surface H H H H H H H H Hydrogen bonds to surface of metal. Break H-H bonds Catalysts
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Pt surface H H H H Catalysts C H H C H H
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Pt surface H H H H Catalysts C H H C H H The double bond breaks and bonds to the catalyst.
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Pt surface H H H H Catalysts C H H C H H The hydrogen atoms bond with the carbon
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Pt surface H Catalysts C H H C H H H H H
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Reversible Reactions Reactions are spontaneous if G is negative. If G is positive the reaction happens in the opposite direction . 2H 2 (g) + O 2 (g) 2H 2 O(g) + energy 2H 2 O(g) + energy 2 H 2 (g) + O 2 (g) 2H 2 (g) + O 2 (g) 2H 2 O(g) + energy
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When I first put reactants together the forward reaction starts. Since there are no products there is no reverse reaction. As the forward reaction proceeds the
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This document was uploaded on 02/06/2011.

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cm4 - Reaction Rate How Fast Does the Reaction Go?...

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