General Chemistry Ch 5. Chemical Kinetics Flashcards
Gibbs Free Energy
Determines whether or not a reaction is spontaneous
Chemical mechanisms
Propose a series of steps that make up the overall reaction
Intermediates
Molecules that exist within the course of a reaction but are neither reactants nor products overall
Rate-determining step
Limits the maximum rate at which the reaction can proceed, the slowest step
Collision theory
States that a reaction rate is proportional to the number of effective collisions between the reacting molecules
Activation energy
Proper orientation and sufficient Kinect energy must be there for a collision to be effective
Arrhenius equation
Mathematical way of representing collision theory
Transition state theory
States that molecules from a transition state or activated complex during a reaction in which the old bonds are partially dissociated and the new bonds are partially formed
Transition state
Highest point on a free energy reaction diagram, the reaction can proceed toward products or revert back to reactants
Activated complex
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Increasing reactant concentration reaction rate
Will increase reaction rate (except for zero-order reactions) because there are more effective collisions per time
Increasing temperature reaction rate
Will increase the temperature because the particles kinetic energy is increased
Changing the medium reaction rate
Can either increase or decrease the reaction rate depending on how the reactants interact with the medium
Adding a catalyst reaction rate
Increases reaction rate because it lowers the activation energy, can either be homogeneous or heterogeneous
Homogeneous catalysts
In the same phase as the reactants
Heterogeneous catalysts
In a different phase than the reactants
Reaction rate measurements
Measured in terms of the rate of disappearance of a reactant or appearance of a product
Rate laws
Take the form of rate = k[A]^x[B]^y, must be determined from experimental data
Rate orders
Do not usually match the stoichiometric coefficients, the sum of all individual rate orders in the rate law
Zero order reactions
Have a constant rate that does not depend on the concentration of the reactant, rate can be changed only by changing the temp or adding a catalyst, concentration vs time curve is a straight line with a slope that equals -k
First order reactions
Have a non constant rate that depends on the concentration of reactant, concentration vs time curve is nonlinear, slope of ln[A] vs time is -k
Second order reactions
Have a non constant rate that depends on the concentration of reactant, concentration vs time curve is nonlinear, slop of 1/[A] vs time is k
Broken-order reactions
Those with noninteger orders
Mixed-order reactions
Those that have a rate order that changes over time
