15TQ: Chemical Equilibrium
Name: _________________________
Text Questions from Brown, et. al.
1. When does chemical equilibrium occur?
2. What happens, such that the reaction appears to be stopped?
15.1
3. Describe an equilibrium state.
4. WHAT equals a constant, at equilibrium?
15.2
5. From which direction can equilibrium be reached?
6. For the equation a A + b B   d D + e E, write the expression that denotes the equilibrium condition
according to the law of mass action.
7. What does the subscript c on the K indicate?
8. By convention, which substances are written where in the equilibrium-constant expression?
9. What does the equilibrium-constant expression depend on, and what does it NOT depend on?
10. On what two things does the value of Kc depend, and on what two things does it NOT depend?
11. What are the units for Kc?
12. For the gaseous reaction given by a A + b B   d D + e E,
write the equilibrium constant in terms of partial pressures.
13. For the expression you wrote in your answer to Q12, what pressure unit should be used?
14. Write the expression that relates Kp and Kc.
15. What is n equal to?
15.3
16. A. What are the relative amounts of products and reactants when K is large?
…when K is small?
B. When K is large, we say that the equilibrium “lies to the _______” If K is small, we say that the
equilibrium “lies to the _______.”
17. At equilibrium, what are equal and what are not?
18. Why is the direction in which we write the equation for an equilibrium reaction arbitrary?
19. For a reaction, how are the Kc for the “forward” reaction and the Kc for the “reverse” reaction related?
20. When stating the value of an equilibrium constant, what two things must be specified?
21. The equilibrium constant for a net reaction made up of two or more steps (i.e., different reactions) is
equal to what?
15.4
22. What is the difference between homogeneous and heterogeneous equilibria?
23. With regard to the equilibrium-constant expression, what is done (or NOT done) with the concentration
of a pure solid or pure liquid?
24. When a solvent is a reactant or product in an equilibrium reaction, what is done (or NOT done) with its
concentration in the equilibrium-constant expression?
15.5
25. Does the value of Kc change with temperature?
15.6
26. What two things does the value of the equilibrium constant (i.e., Kc or Kp) allow you to do?
27. What is the reaction quotient Q?
28. A. For a given reaction, how many values of Kc are possible at any temperature?
B. …how many values of Q?
29. If Q = K, the reaction is at ___________. If Q > K, there are too many ________; the reaction moves to
the ______. If Q < K, there are too many ___________; the reaction moves to the ______.
15.7
30. What does Le Chatelier’s principle state?
31. A system at equilibrium is in a…
32. With regard to Le Chatelier’s principle, what is the relationship between the concentration of a
substance and the equilibrium shift?
33. With regard to Le Chatelier’s principle, what is the relationship between the volume change of a
gaseous mixture and the equilibrium shift?
34. For the reaction H2(g) + I2(g)   2 HI(g),
the position of the equilibrium?
35. What do pressure-volume changes NOT do?
why does changing pressure or volume NOT influence
What DO they do?
36. Essentially every equilibrium constant changes in value as…
37. What could we consider heat to be, in an endothermic reaction?
…in an exothermic reaction?
38. When the temperature of an equilibrium system increases (decreases), the equilibrium shifts in the
direction that _____________ (_____________) heat.
39. For an endothermic (exothermic) reaction, increasing the temperature causes K to _____________
(______________).
40. What does a catalyst increase, and what does it NOT change?
Ch. 16: Acid-Base Equilibria
16.1
41. How did Arrhenius define acids? How did he define bases?
16.2
42. An H+ ion is simply what?
43. When is a hydronium ion formed?
44. What two symbols do chemists use interchangeably?
45. A. For what two reasons do we write H+ rather than H3O+?
B. Which symbol is closer to reality?
46. What is the difference between a Bronsted-Lowry acid and base?
47. To be a B-L acid, what must a substance have? To be a B-L base, what must a substance have?
48. When does an amphiprotic substance act as a base? As an acid?
49. What constitutes a conjugate acid-base pair?
50. What is the relationship between the strength of an acid (or base) and that of its conjugate?
51. In an acid-base reaction, the position of the equilibrium favors what?
52. What happens during the autoionization of water?
53. At 25oC, what is the equation for (and value of) Kw?
54. What is the relationship between [H+] and [OH–] in acidic solution? In basic solution?
55. Write the equation for calculating pH.
56. Which are the ONLY significant figures in a logarithm?
57. A change by one unit of pH reflects a change in [H+] of what?
58. Write the equation for calculating pOH AND the one that (at 25oC) connects the pH with the pOH.
16.5
59. Write the formulas of the seven strong acids.
60. Why are equilibrium arrows NOT used to exemplify the behavior of strong acids?
61. Why is calculating the pH of a solution of a strong monoprotic acid a straightforward process?
62. Besides the hydroxides of the alkali metals and the heavier alkaline earths, OH – ions are also produced
when certain substances – containing WHICH ion – react with water?