Principles of Chemistry IICHEM 1212Chapter 12

1. Give two examples of each of the following: a gaseous solution, a liquid solution, a solid solution.

2. What two factors are needed to explain the differences in solubilities of substances?

3. What is solvation? Describe the process of dissolving a sodium chloride crystal in water.

4. What is the usual solubility behavior of an ionic compound in water when the temperature is raised?

5. Give an example of each: a salt whose heat of solution is exothermic and a salt whose heat of solution is endothermic.

6. What do you expect to happen to a concentration of dissolved gas in a solution as the i) pressure is decreased and ii) solution is heated.

7. Pressure has an effect on the solubility of oxygen in water but negligible effect on the solubility of sugar in water. Why?

8. What does it mean to say that two liquids are miscible?

9. Explain why ethanol (C2H5OH) is not soluble in hexane (C6H12).

10. Explain why naphthalene (C10H8) is more soluble in benzene (C6H6) than CsF.

11. Explain on the basis that “like dissolves like” why glycerol (CH2OHCHOHCH2OH) is miscible in water but benzene (C6H6) has very limited solubility in water.

12. Arrange the following compounds in order of increasing solubility in water: O2, LiCl, Br2, CH3OH.

13. Arrange the following compounds in order of increasing solubility in hexane (C6H14): CH2OHCH2OH, C10H22, H2O.

14. Four physical properties change when a solute is dissolved in a solvent. What is the name given to these physical properties? State these four properties.

15. Explain why the boiling point of a solution containing a nonvolatile solute is higher than the boiling point of a pure solvent.

16. How would you prepare 72.5 g of an aqueous solution that is 2.50% potassium iodide by mass?

(1.81 g KI with 70.7 g H2O)

17. Vanillin, C8H8O3, occurs naturally in vanilla extract and is used as a flavoring agent. A 39.1-mg sample of vanillin was dissolved in 168.5 mg of diphenyl ether (C6H5)2O. What is the molality of vanillin in the solution? (m= 1.53 m)

18. Fructose (C6H12O6) is a sugar occurring in honey and fruits. The sweetest sugar, it is nearly twice as sweet as sucrose (cane or beat sugar). How much water should be added to 3.50 g of fructose to give a 0.125 m solution? (155 g water)

19. A bleaching solution contains sodium hypochlorite (NaClO) dissolved in water. The solution is 0.650 m NaClO. What is the mole fraction of NaClO? (0.0117)

20. A solution of vinegar is 0.763 M acetic acid, HC2H3O2. The density of the vinegar is 1.004 g/mL. What is the molal concentration of acetic acid? (0.796 m)

21. A beverage contains tartaric acid, H2C4H4O6, a substance obtained from grapes during wine making. If the beverage is 0.271 M tartaric acid, what is the molal concentration? The density of the solution is 1.016 g/mL. (2.78 x 10-4 m)

22. An aqueous solution is 27.0% lithium chloride by mass. The density of the solution is 1.127 g/mL. What are the molality, mole fraction, and molarity of the LiCl in the solution? (8.73 m; 7.18 M; 0.157)

23. A 75-g sample of a gaseous fuel mixture contains 0.51 mole fraction propane (C3H8); the remainder of the mixture is butane (C4H10). What are the masses of propane and butane in the sample? (C3H8: 33 g, C4H10: 42 g)

24. A solution is prepared by mixing 62.6 mL of benzene (C6H6) with 80.3 mL of toluene (C7H8). Calculate the mole fractions of these two components. The densities are 0.879 g/cm3 for benzene and 0.867 g/cm3 for toluene.

(Benzene 0.482; Toluene 0.518)

25. Calculate the molarity, molality, and mole fraction of NH3 for a solution of 30.0 g of NH3 in 70.0 g of water. The density of the solution is 0.982 g/mL. (17.3 M; 25.1 m; 0.312)

26. A dilute aqueous solution containing 1.00 ppm of solute has a density of 1.00 g/mL. Express the concentration of solute in g/L, μg/L, μg/mL, mg/mL. (1.00 e-9 g/L, 1.00 e-3 μg/L, 1.00 μg/mL, and 1.00 e-3 mg/mL)

27. The concentration of C20H42 (MM = 282.55 g/mol) in winter rainwater is 0.2 ppb. Assuming that the density of rainwater is close to 1.00 g/mL, find the molar concentration of C20H42(7 x 10-11 M)

28. How many grams of urea (H2NCONH2) must be added to 450.0 g of water to give a solution with a vapor pressure 2.50 mmHg less than that of pure water at 30 oC? The vapor pressure of pure water at 30 oC is 31.8 mmHg. (130 g)

29. What are the boiling and freezing points of a 2.47 molal solution of naphthalene in benzene? The boiling point and freezing point of benzene are 80.1 oC and 5.5 oC, respectively. The constants for bezene are kb = 2.53 oC/m and kf = 5.12 oC/m(86.3oC; -7.1oC)

30. An aqueous solution contains amino acid glycine (NH2CH2COOH). Assuming no ionization of the acid, calculate the molality of the solution if it freezes at -1.1 oC (kf for water = 1.86 oC/m). (0.59 m)

31. A solution of 6.85 g of a carbohydrate in 100.0 g of water has a density of 1.024 g/mL and an osmotic pressure of 4.61 atm at 20.0 oC. Calculate the molar mass of the carbohydrate. (342 g/mol)

32. A solution of an organic solid is extracted from gum arabic and analyzed. A solution of 0.650 g of the solid in 27.8 g of the solvent diphenyl gave a freezing-point depression of 1.56 oC. Calculate the molar mass of the solid (kf for diphenyl = 8.00 oC/m). (1.20 x 102g/mol)

33. What is the osmotic pressure (in atm) of a 1.36 M aqueous solution of urea at 22.0 oC. (32.9 atm)

34. A solution containing 0.8330 g of a protein of unknown structure in 170.0 mL of aqueous solution was found to have an osmotic pressure of 5.20 mmHg at 25 oC. Determine the molar mass of the protein. (1.75 x 104 g/mol)

35. Urea, (NH2)2CO, is dissolved in 100.0 g of water. The solution freezes at -0.085 oC. How many grams of urea were dissolved to make the solution? (0.280 g)

36. In a mountainous location, the boiling point of pure water is found to be 95 oC. How many grams of sodium chloride must be added to 1 kg of water to bring the boiling point back to 100 oC? Assume that i = 2. (290 g)

37. Differentiate between an ideal solution, a solution with positive deviation from Raoult’s law, and a solution with negative deviation from Raoult’s law. Sketch the pressure versus mole fraction curves to illustrate your explanations.