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20 Cards in this Set
- Front
- Back
Factors Affecting Reaction Rates
Particle Size |
*the smaller the particle size, the larger the surface area for a given mass of particles
-an increase in surface area increases the amount of reactant exposed for reaction -this increases the collision frequency and therefore the reaction rate *one way to increase surface area is to dissolve reactants -this separates the particles and makes them more accessible to other reactants |
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Collision Theory
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atoms, ions, and molecules can react to form products when they collide, provided that the particles have enough kinetic energy
*particles lacking the necessary kinetic energy to react bounce apart when they collide |
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activation energy
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*the minimum amount of energy that particles must have in order to react
-acts as a barrier that reactants must cross to become products |
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activated complex
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*the arrangement of atoms at the peak of the activation-energy barrier
-lifetime is typically about 10e-13 seconds -very unstable: is as likely to form products as it is to re-form reactants -also called the transition state |
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Factors Affecting Reaction Rates
Temperature |
*Raising the temperature speeds up reactions
-directly related *at higher temperatures, particles move faster and are more chaotic -therefore, they have enough energy to react when they collide -more colliding particles are energetic enough to slip over the activation-energy barrier |
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Factors Affecting Reaction Rates
Concentration |
*cramming particles into a fixed volume increases the concentration of reactants, the collision frequency, and therefore the reaction rate
*increase in concentration=increase in reaction rate -directly related |
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catalyst
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substance that increases reaction rate w/o being used up itself in the reaction: allows reactions to proceed at a lower energy than is required
*catalysts lower the activation-energy barrier *often written above the yield arrow |
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inhibitor
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substance that interferes with the action of a catalyst
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chemical equilibrium
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*a state in which the forward and reverse reactions take place at the same rate
-concentrations of the components on both sides of the chemical equation are not necessarily the same |
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equilibrium position
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*given by the relative concentrations of the system's components at equilibrium
-indicates whether the components on the left or right side of a reversible reaction are at a higher concentration |
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Le Chatelier's Principle
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*if a stress is applied to a system in dynamic equilibrium, the system changes to relieve the stress
-stresses include concentration, temperature, and pressure |
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effect of Pressure on equilibrium position
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Increase in pressure:
-shift moves toward lower number of moles Decrease in pressure: -shift moves toward higher number of moles |
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effect of Concentration on equilibrium position
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(Pg. 542)
*removing a product always pulls a reversible reaction in the direction of products (use up reactants and achieve original ratio) (same as removing reactants) *adding a product always pushes a reversible reaction in the direction of reactants *the ratio shifts in order to achieve the original 99:1 etc. *see notecard* |
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effect of Temperature on equilibrium position
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(ADD HEAT: SHIFT LEFT)
2SO2 + O2 = 2SO3 + HEAT (REMOVE HEAT: SHIFT RIGHT) |
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equilibrium constant (Keq)
Keq= [C]c x [D]d [A]a x [B]b |
aA + bB = cC + dD
*the ratio of product concentrations to reactant concentrations at equilibrium, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation *does not include solids or liquids* |
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rate law
Rate = k[A]a[B]b (a and b are exponents) |
*specific rate constant (K) - a proportionality constant relating the concentrations of reactants to the rate of the reaction
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first-order reaction
(sum of exponents = 1st, 2nd, 3rd, etc. reaction) |
*the reaction rate is directly proportional to the concentration of only one reactant
-as a first-order reaction progresses, the rate of the reaction decreases [A]1 = first order -initial concentration is directly related to initial rate 0.30 - 0.60 O.O80 - O.160 |
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elementary reaction
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reactions are converted to products in a single step (a one step reaction)
-has only one activated complex and thus only one activation-energy peak # of intermediates +1 = # of elementary reactions (count the number of arrows) |
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reaction mechanism
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*includes all the elementary reactions of a complex reaction
-reaction progress curve resembles hills and valleys reactant+reactant=product which then = reactant=product: 2 elementary reactions; 1 reaction mechanism |
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intermediate
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a product of a reaction that becomes a reactant of another reaction
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