Kinetics pdf

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Created by
Daniella

Cards (30)

  • What area of chemistry concerns reaction rates?
    Chemical kinetics
  • What are spontaneous reactions?
    Reactions that will happen, but speed is unknown
  • How is reaction rate defined?
    Change in concentration per unit time
  • What is the formula for calculating reaction rate?
    Rate = (conc. of A at t2 - conc. of A at t1) / (t2 - t1)
  • What happens to the concentration of N<sub>2</sub> in the reaction 2 N<sub>2</sub> + 3 H<sub>2</sub> → 2 NH<sub>3</sub> as it progresses?
    It decreases at a rate of 1/3
  • What is the difference between average rate and instantaneous rate?
    Average rate is over long intervals; instantaneous is at a point
  • What is the significance of the initial rate method?
    Measurements are taken as soon as reactants are mixed
  • What does the rate law express?
    How rate depends on concentration
  • Why do products not appear in the rate law?
    Because the reverse reaction does not contribute
  • What must be determined experimentally in rate laws?
    The value of the exponent n
  • What are the two types of rate laws?
    • Differential Rate Law: how rate depends on concentration
    • Integrated Rate Law: how concentration depends on time
  • How do you determine the rate law from experimental data?
    Analyze the initial rates and concentrations
  • What is the overall reaction order?
    Sum of the order of each component in the rate law
  • What is the integrated first-order rate law equation?
    ln[A] = -kt + ln[A]<sub>0</sub>
  • What indicates a first-order reaction on a graph?
    A straight line when plotting ln[A] versus time
  • What indicates a second-order reaction on a graph?
    A straight line when plotting 1/[A] versus time
  • What is the half-life for a first-order reaction?
    t<sub>1/2</sub> = ln2/k
    • Does not depend on concentration
  • What is the half-life equation for a second-order reaction?
    t<sub>1/2</sub> = 1/k[A]<sub>0</sub>
  • What is the half-life equation for a zero-order reaction?
    t<sub>1/2</sub> = [A]<sub>0</sub>/2k
  • What is a reaction mechanism?
    A series of steps by which a reaction occurs
  • What is an intermediate in a reaction mechanism?
    Formed in one step and used in another
  • What is molecularity?
    Number of species colliding to produce a reaction
  • What is the rate-determining step (RDS)?
    The slowest elementary step in a reaction
  • How does the collision model explain reaction rates?
    Molecules must collide to react, but not all collisions lead to reactions
  • What is the Arrhenius equation used for?
    To show how rate depends on temperature and activation energy
  • What effect does temperature have on reaction rates?
    Higher temperature increases the reaction rate
  • What is a catalyst?
    A substance that speeds up a reaction without being consumed
  • What is the difference between homogeneous and heterogeneous catalysts?
    Homogeneous catalysts are in the same phase; heterogeneous are in different phases
  • How do catalysts work?
    • Allow reactions to proceed by a different mechanism
    • Provide a new pathway with lower activation energy
    • Do not change the enthalpy of the reaction
  • What happens to the rate of reaction when more reactants are added beyond a certain point?
    The rate will not change and becomes zero order