40 Cards in this Set
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What is chemical kinetics?
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The study of reaction rates, including how reaction rates change with varying conditions and which molecular events occur during the overall reaction.
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What is rate?
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How much a quantity changes in a given period of time
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Rate is equal to what?
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Change in concentration/ Change in time
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For the reaction rate for reactants what is placed in front of the definition?
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Negative sign
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The rate term needs to always be what?
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Positive
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What is equilibrium?
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In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present at concentrations which have no further tendency to change with time. Usually, this state results when the forward reaction proceeds at the same rate as the reverse reaction. The rea…
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For a chemical reaction to occur you must have what three things?
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A collision, sufficient energy, and correct orientation
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What is the average rate?
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The change in measured concentrations in any particular time period
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The larger the time interval, the more the average rate ______ from the instantaneous rate.
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Deviates
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What is the instantaneous rate?
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The change in concentration at any one particular time
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What is initial rate?
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Tangent to the curve at time zero
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What factors affect reaction rate?
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Nature of the reactants (what kind of reactant molecules (size) and what physical condition they are in), temperature (increase temp increases rate), catalysts (affect speed of reaction), and concentration (the larger the concentration of reactant molecules, the faster the reaction)
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What do catalysts do?
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Lower the amount of energy needed for a successful collision (without bein consumed)
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Higher pressure leads to what?
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Higher concentration
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The rate constant stays the same as long as what else stays the same?
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Temperature
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What is the rate law of a reaction?
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The mathematical relationship between the rate of the reaction and the concentrations of the reactants.
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What is the order of the reaction?
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The sum of the exponents on the reactants in the rate law
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Rate laws are always determined how?
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Experimentally
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Reaction order is always defined in terms of what?
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Reactant concentrations
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Are zero, negative, and fractional orders possible in the rate law?
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Yes
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The concentration of a reactant with a zero order dependence has _____ on the rate of the reaction.
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No effect
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Rate expressions have no what?
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Rate constant
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Rate laws do not have what?
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Time
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The half-life (t1/2) of a reaction is what?
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The length of time it takes for the concentration of the reactants to fall to 1/2 (50%) of its initial value (concentration)
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Which order's half-life has no concentration effects?
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First order
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All radioactive decay is what order?
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First order
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Catalysts provide what?
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An alternate mechanism for the reaction to occur
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In general a catalyst lowers what?
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The energy of activation
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Lowering the activation energy increases what?
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The rate constant, k, and the rate of the reaction
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What are homogeneous catalysts?
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Catalysts that are in the same phase as the reactant particles (ex. both in (g) phase)
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What are heterogeneous catalysts?
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Catalysts that are in a different phase than the reactant particles
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What are enzymes?
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Protein molecules that catalyze biological reactions (biological catalysts)
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How do enzymes work?
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They absorb the substrate reactant onto an active site that orients it for reaction
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What is chemical equilibrium?
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The state reached when the concentrations of reactants and products remain constant over time
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What is dynamic equilibrium?
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The condition wherein the rates of the forward and reverse reactions are equal
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What are the units for K?
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No units necessary units for K are meaningless
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When dealing with equilibrium reactions what states of matter are not considered apart of equilibrium?
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Liquids and solids
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When does the equilibrium constant, K, change?
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When temperature changes
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The concentration of a gas in a mixture is proportional to what?
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Its partial pressure
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What guides us in predicting the effect various changes in conditions have on the position of equilibrium?
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Le Chatelier's Principle
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CHM 170: Final Exam Study Guide