Honors Chemistry Thank you Mrs. Post!
Chapter 15: Chemical Equilibrium
Picture taken from http://remijones.deviantart.com/art/Chemical-Equilibrium-Poem-298780206
Objectives: The student will be able to:
Explain the concept of chemical equilibrium. Define the equilibrium constant and learn how to write equilibrium-constant expressions for homogeneous and heterogeneous reactions. Interpret the magnitude of an equilibrium constant. Calculate the value of an equilibrium constant using equilibrium concentrations of reactants and products. Use equilibrium constants to predict the equilibrium concentrations of reactants and products. Determine the direction a reaction must proceed in order to achieve equilibrium. Use Le Chatelier’s principle to predict how a system at equilibrium responds to changes in concentration, volume, pressure and temperature. 15.1 – The Concept of Equilibrium (pg. 629-631)
1. Chemical equilibrium occurs when:
2. Why does it appear as though a reaction has stopped when equilibrium is reached?
3. What does a double arrow (⇄) signify in a chemical reaction?
4. What letter is used to represent the constant in a rate law?
5. What three important lessons regarding equilibrium are learned from example reaction 15.1?
6. Copy Figure 15.2 below and give a brief explanation of what is occurring in each graph. 15.2 – The Equilibrium Constant (pgs. 632-637)
7. According to the law of mass action, provide the expression for the equilibrium conditions for the general equation a A + b B ⇄ c C + d D. Be sure to label each component and explain how it was obtained.
8. Give the equilibrium-constant expression for the Haber process, N2(g) + 3 H2(g) ⇄ 2 NH3(g).
9. On what does the equilibrium-constant expression depend? On what does it not depend?
10. When the reactants and products in a chemical reaction are gases, we can formulate the equilibrium-constant expression in terms of partial pressures instead of molar concentrations.
Give the general expression for Kp. Be sure to label each component and explain how it was obtained.
15.3 – Interpreting and Working with Equilibrium Constants (pgs. 637-640) 11. Explain how the magnitude of the equilibrium constant can be used to determine which side of a chemical equation is predominating. 15.4 – Heterogeneous Equilibria (pgs. 641-643) 12. Explain the difference between homogeneous equilibria and heterogeneous equilibria.
13. What do we do with pure solids and pure liquids when determining the equilibrium-constant expression for a reaction? Provide the two explanations as to why this is the case.
14. When a solvent is involved as a reactant or product in an equilibrium, its concentration is also ______from the equilibrium-constant expression, provided the concentrations of the reactants and products are ______, so that the solvent is essentially a pure substance.
15.5 – Calculating Equilibrium Constants (pgs. 643-645) 15. What are the four steps for using a known equilibrium concentration of at least one species in a reaction to deduce the equilibrium concentrations of the others through stoichiometry? 16. Read through Sample Exercise 15.9. We will complete “ICE” tables like the one found in this example as a class.
15.6 – Applications of Equilibrium Constants (pgs. 646-649) 17. In addition to indicating the extent to which a reaction will proceed, what two things does the equilibrium constant allow us to do?
18. Define the reaction quotient, Q.
19. List the three possible situations that arise when we compare the values of Qc and Kc (or Qp
and Kp). It is useful to draw Figure 15.9 as a visual representation to support the description of each situation. 20. Read through Sample Exercise 15.11. We will complete problems such as this example as a class.
15.7 – Le Chatelier’s Principle (pgs. 649-658) 21. Le Chatelier’s principle can be stated as follows:
22. Explain how a change in reactant or product concentration would shift an equilibrium in an attempt to maintain a new state of balance.
23. Explain how a change in volume (and ultimately pressure) would shift an equilibrium in an attempt to maintain a new state of balance.
24. Explain how a change in temperature would shift an equilibrium in an attempt to maintain a new state of balance. 25. Explain the effect the addition of a catalyst would have on a chemical system that is at equilibrium.