Unit 5: Kinetics.

5.1 Reaction Rates.

Write the mathematical formula for the rate of appearance or disappearance of a species in a chemical reaction as a change in concentration over time, considering stoichiometric factors.

  1. Write the rate expression for the disappearance of A in the reaction 2A → B.

Determine the rate of the overal reaction from the rate of disappearance of a reactant or appearance of a product

  1. For the reaction: 2A → B. Find the overall rate of the reaction if the rate of appearance of B is 0.025 Ms-1.

Justify how a chage in conditions (surface area, concentration/pressure, temperature, presence of a catalyst) will affect the rate of the reaction.

  1. Explain why increasing temperature generally increases the rate of reaction.

5.2 Introduction to Rate Law.

Know the meaning of zero, first, and second-order reactions.

  1. What does it mean if a reaction is first-order with respect to [A]?

Write a rate law for a reaction using initial rate data from multiple trials.

  1. Determine the rate of the reaction: X + Y → XY
    Trial Initial [X] Initial [Y] Initial Rate of Appearance of XY Ms-1
    1 0.01 0.01 0.005
    2 0.01 0.02 0.010
    3 0.02 0.01 0.025

Determine the overall order of the reaction by adding the powers of the reactant concentrations in the rate law.

  1. What is the overal order the reaction who's rate law is: rate = k[A]2[B]?

Calculate the value of the rate constant (k) and express it with the correct units.

  1. question coming soon.

Understand that the rate constant (k) is dependant on temperature and therefore specific to a temperature.

  1. If a reaction is increased from 300K to 400K would the rate constant (k) increase, decrease, or remain constant?

5.3 Concentration Changes Over Time.

Determine the order of a reaction by examining graphs of [A] vs. t, ln [A] vs. t, and 1/[A] vs. t.

  1. Which graph is linear for a second-order reaction?

Use the integrated rate law corresponding to the order of a reaction to determine the value of k.

  1. Use the first-order integrated rate law to calculate k from experimental data.

Recognize that the half-life of a first-order reaction is constant.

  1. Why does the half-life of a first-order reaction not depend on the initial concentration?

Apply the half-life equation for a first-order reaction to determine k or the half-life of a reaction, including radioactive decay.

  1. Calculate the half-life of a reaction with k = 0.0030 s-1.

5.4 Elementary Reactions.

Use coefficients of elementary steps to determine the rate law.

  1. Write the rate law for the elementary step A + B → C.

5.5 Collision Model.

Use collision theory to justify whether a reaction will proceed under given conditions.

  1. Why does a higher temperature lead to more effective collisions?

Examine Maxwell-Boltzmann distributions to determine the likelihood of successful collisions in a reaction.

  1. How does increasing temperature affect the Maxwell-Boltzmann distribution curve?

5.6 Reaction Energy Profile.

Label the areas on a reaction energy profile: reactants, transition state, products, activation energy.

  1. Identify the activation energy on a reaction energy diagram.

Apply the Arrhenius equation qualitatively to discuss how temperature affects the rate of an elementary reaction.

  1. According to the Arrhenius equation, what happens to k as T increases?

5.7 Introduction to Reaction Mechanisms.

Label the components of a reaction mechanism: reactants, products, intermediates, catalysts.

  1. Which species in a mechanism is consumed and then regenerated?

Determine if a provided reaction mechanism is valid for a given reaction.

  1. What must the sum of the elementary steps in a mechanism equal?

5.8 Reaction Mechanism and Rate Law.

Use the slow step of a mechanism to write the rate law for the overall reaction.

  1. How is the rate-determining step used to write the rate law?

5.9 Pre-Equilibrium Approximation.

Use fast equilibrium expressions to substitute species in rate laws to match an overall reaction description.

  1. Why are equilibrium expressions used for fast steps in mechanisms?

5.10 Multistep Reaction Energy Profile.

Draw a reaction energy profile with relative features that match given conditions.

  1. Sketch an energy profile showing a reaction with high activation energy.

5.11 Catalysis.

Explain how a catalyst works.

  1. How does a catalyst affect the activation energy of a reaction?

Modify a reaction profile to show the effect of a catalyst.

  1. Draw a reaction profile with and without a catalyst.

Identify the presence of a covalent bond between a catalyst and a reactant or intermediate.

  1. What does the temporary bond between a catalyst and reactant do to the reaction pathway?
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