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Reaction Rates
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Kinetics is the branch of chemistry dealing with reaction rates.
Kinetics help chemists understand underlying mechanism by which the reaction occurs.
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How Do we Speed up Chemical Reactions?
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Reaction Rates rate at which a chemical reaction takes place
measured by the rate of formation of a product or disappearance of a reactant rate of a rxn changes with time during the rxn fastest at beginning and slowest at end
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Factors Affecting Rate
concentration pressure temperature surface area catalysts
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Concentration Particles must collide in order to react.
Reaction rates increase when concentrations increase. More particles(greater concentration) = more likely collisions will occur. If concentration is doubled # of collisions will double. As reaction proceeds, reactants are consumed, concentration declines, and rate decreases
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Pressure Doubling the pressure of a gas doubles its concentration so reaction rate increases
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Temperature Greatly effects rate
When the temp is high, particles move faster so more collisions More collisions = increased rate
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Surface Area More surface area = more collisions
More collisions = higher rxn rate Smaller particles gives more surface area Powder form has highest rxn rate
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Reaction Pathways and Activation
For 2 particles to rxt, they must collide violently enough to overcome the repulsion of their electrons. Only particles with enough kinetic energy are likely to rxt. activation energy, Ea minimum energy 2 colliding particles need to rxt.
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Catalysts Speed up reaction by reducing activation energy
Not changed or used in the reaction
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Enzymes Proteins that catalyze metabolic activity
Ex: lactase catalyzes reaction of lactose (sugar in milk). People that don’t produce lactase have lactose intolerance
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Bombardier Beetle
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