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Chemistry LibreTexts

Midterm 1 Expectations

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  • This is more comprehensive overview of expectations from the first 9 lectures with respect to mid-term 1. This list should be augment by homework.

    Lecture 1

    What are the basic assumptions in Kinetic Molecular Theory?

    What is an elastic vs. inelastic collision?

    How is the average Kinetic Energy of an ensemble of thermalized gas particles related to temperature (equipartition principle)?

    How is pressure related to microscopic properties of a gas?

    You should be able to compare the Ideal Gas law (phenomenological) results to the kinetic molecular theory (microscopic) regarding pressure, kinetic energy and temperature.

    You should understand the basics of the Maxwell-Bolzman distribution, the relationships of the most-probable, root-meat square,and average (or mean) velocities and how they are derived (I don't care about the details of solving the integrals).

    Lecture 2

    What is a collisional cross-section of a gas particle?

    How do you calculate the collisional frequency of a gas particle?

    How does the collisional frequency vary as a function of molecular mass, temperature, pressure, density and time of the day?

    What is the mean free path and how is it calculated and depend on the above factors?

    What is the difference between effusion and diffusion?

    How to use Graham's law of effusion? And how to derive this law.

    Lecture 3

    Definition of a reaction rate for an arbitrary reaction.

    Relate the reaction rate to the growth or decay rates of reactants or products, respectively.

    Difference between average reaction rate and instantaneous rate

    Define Reaction Order for a reaction.

    How do you determine the reaction order from the balanced reaction equation?

    Lecture 4

    What is the differential and integral forms of the rate laws for the 0th, 1st, and 2nd order reactions?

    • How do you derive the integral forms of the rate laws for these cases ?
    • What are the units of the rate constants for these cases?
    • What is the relationship between initial concnetratiosn and half-life for each of these cases?

    What sorts of plots (from experimental time-dependent concentration data) do you construct to confirm the reaction order of a reaction?

    How to use the method of initial rates to determine the reaction order of a reaction (hint: this is working with the differential form and the above question involves the integral form).

    Lecture 5

    Definition of an elementary step, molecularity and reaction mechanism.

    Relationship between molecularity of a reaction and it's rate law.

    What is the probability of a termolecular step to occur and why?

    What is a rate determining step?

    What is an intermediate?

    How does a rate law depend on an intermediate population?

    Lecture 7

    For any proposed mechanism, be able to construct the differential rate laws describing relevant for the species the reaction.

    Solving is typically difficult for a multiple mechanism; what approximations can be used:

    • Steady-state approximation
    • Equilibrium approximation

    Demonstrate these approximation in action.

    Basics of a chain reaction mechanism.

    Lecture 8

    Temperature dependence of a reaction:

    • What is the Arrhenius equation?
    • What is the activation barrier? What is the pre-exponential constant? Which are dependent on temperature?
    • Where does the energy come from in overcoming an activation barrier?
    • Use the Arrhenius equation to identify rate constants at new temperatures

    What is a potential energy surface (PES)?

    How is the PES related to the reaction profile? How to identify the acativated complex on the PES.

    Lecture 9

    Compare basic principles of collision theory vs. transition state theory.

    How to derive the primary equation in both theories and where terms come from.

    What is a steric factor? What range is possible for this?

    How to apply both theories.

    Is the pre-exponential constant, A, dependent on temperature? Answer in context of TST.