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7 .4 : reaction rates and equilibrium

7 .4 : reaction rates and equilibrium. Factors affecting reaction rates. Think about the following observations: A potato slice takes 5 minutes to cook at 200° C but takes 10 minutes to cook at 100 ° C. Therefore potatoes cook faster at higher temperatures.

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7 .4 : reaction rates and equilibrium

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  1. 7.4: reaction rates and equilibrium

  2. Factors affecting reaction rates • Think about the following observations: • A potato slice takes 5 minutes to cook at 200° C but takes 10 minutes to cook at 100 ° C. Therefore potatoes cook faster at higher temperatures. • Potato slices take 10 minutes to cook, but whole potatoes take about 30 minutes to cook. Therefore, potatoes cut into smaller pieces cook faster • These have to do with the speed of reactions

  3. Factors affecting reaction rates • Anything that increases contact between particles will increase the rate of a reaction • 1) higher temperatures speed up reactions • Particles move faster at higher temperatures • Faster moving particles collide more often, so there is a greater chance for the particles to react

  4. Factors affecting reaction rates • 2) A large surface area speeds up rxns • Cutting up a potato exposes inner area • 3) Higher concentrations of reactants speed up rxns • Ex) the more wood you put on a fire, the more it will burn • 4) Higher pressure increases speed of rxns • Because there is less space in which the particles can move • 5) Smaller molecules react quicker

  5. catalysts • A catalyst speeds up or slows down a rxn but is not changed by the rxn • IF it slows down the rxn, it’s called an inhibitor • Enzymes are catalysts for chemical rxns in living things • Most enzymes provide a surface for the reaction to occur • Substrate – the reactant that is catalyzed, or acted on, by the enzyme

  6. Equilibrium • Reactions that go in both directions • Chemical equilibrium – a state in which a reversible chemical rxn is proceeding in both directions equally • Symbolized by double arrows • Ex) CaCO3CaO + CO2

  7. equilibrium • Le Chatelier’s Principle – if a change is made to a system in chemical equilibrium, the equilibrium shifts to oppose the change until a new equilibrium is reached.

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