WebLecture: Disturbing an Equilibrium State

Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 15: Sections 5-6.

1. 15.5 In many analyses, we recognize that an overall reaction is a sequence of steps. We may need to multiply a reaction's coefficients or reverse it to achieve the net desired overall reaction. These manipulations affect the equilibrium constant of the reaction step.
   • Changing the stoichiometric coefficients by multiplying through a reaction equation will change the equilibrium constant by an exponential factor. For example, if we double the reaction coefficients, the equilibrium constant will be squared.
   • If we reverse a chemical reaction, the products and reactants switch places in the ratio for the equilibrium constant. The equilibrium constant for a reverse reaction is the inverse of the forward reaction equilibrium constant: K_reverse = 1 / K_forward.
2. 15.6 If a system at equilibrium is disturbed, it will try to establish a new equilibrium by mitigating the effect of the disturbance as much as possible. A disturbance could include changes in temperature, the addition of a reactant or product, or in gases, changes in volume.

Videos for Chapter 15: Principles of Chemical Reactivity: Equilibria

Review the Videos at Thinkwell Video Lessons.

• Under "Chemical Equilibrium"
  • Shifting Chemical Equilibrium
    • Le Chatelier's Principle
    • The Effect of Changing Amounts on Equilibrium
    • The Effect of Pressure and Volume on Equilibrium
    • The Effect of Temperature and Catalysts on Equilibrium

Homework problems: See your Moodle assignment!

AP #12 GUIDED INQUIRY — Determining the rate law — Phase II

Run the experiment you designed in Phase I at least twice at different temperatures, and at least twice at different concentrations. Analyze your data, and predict what will happen if you increase or decrease temperature, and increase or decrease one of the reactants. Test your predictions by doing a third run for each change.

Resources:

• IGHCE Lab 12.3 Determination of the effect of Concentration on Reaction Rate
• HSCKM VI-3 Determining a Reaction Order
• APGIE Investigation 11: What Is the Rate Law of the Fading of Crystal Violet Using Beer’s Law
• There is no alternative form of this lab.

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