Answers to UNIT 7 Self Test:

1. b    2. ae    3. ac    4. c    5. ab    6. d    7. e    8. bc    9. ad    10. a

11. a: sugar does not form ions in solution.

12. a: NaCl form ions in solution and can conduct a current.

13. a: Gases are less soluble at higher temperatures.

14. c: Temperature affects both amount of and rate at which solid solutes dissolve.

15. c: since 30/100 > 70/250

16. a: More solvent will increase the volume of solution but leave the moles of solute unchanged.

17.b: .20 mol/.200 L = 1.0 M

18. b: solubility measures how much of a solute can dissolve in a given amount of solvent under the given conditions.

19. a: Since Al₂(SO₄)₃ forms the most number of solute particles per mole of compound.

20. c: pressure and solubility of gases are directly proportional.

21. c: this is the definition.

22. c: This is the definition.

23. b: aqueous relates to water solvent.

24. c: Precipitate is a crystallization of a solid from a solution.

25. a: Two dissolved ionic compounds switch partners and form an insoluble salt which precipitates.

26. a: B^- and C⁺ don't change state or form in the course of the reaction.

27. 0.159 M         28. 1.06 M        29.0.00383 mol ClO₄^-         30. 0.604 M

31. 0.101 M        32. 51.3 g        33. 1.74 x 10^-5M CrO₄^2-        

34. Crushed salt has more surface area than can be exposed to the solvent, water, allowing the salt to dissolve faster.

35. (a) K₂CO₃(s) --> 2K⁺(aq) + CO₃^2-(aq)
      (b) Pb²⁺(aq) + 2Br^-(aq) --> PbBr₂(s)
      (c) Ag₂SO₄(s) <--> 2Ag⁺(aq) + SO₄^2-(aq)

36.  3K₂S(aq) + 2Cr(NO₃)₂(aq) --> 6KNO₃(aq) + Cr₂S₃(s)
       Total: 6 K⁺(aq) + 3S^2-(aq) + 2Cr³⁺(aq) + 6NO₃^-(aq) --> 6 K⁺(aq) + 6NO₃^-(aq) + Cr₂S₃(s)
       Net: 3S^2-(aq) + 2Cr³⁺(aq)  -->  Cr₂S₃(s)

Answers to Chapter 16 Self Test Questions

1.  (a) NT    (b) ST; true when gases are present    (c) NT    (d) AT    (e) AT

2.  K_eq= 7.1    3.  [A] = .12 mol/L

4.  (a) Rxn shifts toward reactants ( <----) in order to use up some Cl₂ and restore equilibrium.

      (b) Rxn shifts toward reactants ( <----) in order to form more O₂ and restore equilibrium.

      (c)  Rxn shifts toward products (--->) in order to reduce the total number of moles of gas and restore equilibrium.

       (d)  There is no change in the position of the equilibrium; a catalyst only speeds up both the forward and reverse reactions.

5.  K_eq = .12        6.  [Al³⁺] = 1.8 x 10^-9M,  [OH^-] = 5.5 x 10^-9 M

7.  The solubility equilibrium looks like this:  AgCl(s) <---> Ag⁺(aq)  +  Cl^-(aq) .  When HCl is added, the common ion, Cl^-, throws off the equilibrium.  The reaction shifts toward the reactants in order to use up some of the added Cl^- and restore equilibrium.  The overall effect reduces AgCl 's ability to dissolve and more of this precipitate forms as the result of the added HCl.

8.  If 1.2 g of SrCrO₄ dissolve per liter then by dividing this mass by the MM of SrCrO₄ we can calculate how many moles of SrCrO₄ dissolve per liter of solution.  Since [Sr²⁺] = [CrO₄^2-] = [dissolved SrCrO₄],  K_sp = 3.5 x 10^-5.

9.  A ppt forms if the product of the ion concentrations is greater than the K_sp.  5.0 x 10^-9 < (0.0015 M) x (0.00070 M) so a precipitate does form.