Name Date Class PROPERTIES OF SOLUTIONS

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1 16.1 PROPERTIES OF SOLUTIONS Section Review Objectives Identify the factors that determine the rate at which a solute dissolves Identify the units usually used to express the solubility of a solute Calculate the solubility of a gas in a liquid under various pressure conditions Identify the factors that determine the mass of solute that will dissolve in a given mass of a solvent Vocabulary saturated solution solubility unsaturated solution miscible immiscible supersaturated solution Henry s law Key Equation S Henry s law: 1 S 2 P 1 P 2 Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. Changes in the temperature of a system and 1 of a 1. solute alter the 2 at which a solute dissolves. The extent 2. to which a gas dissolves in a liquid is proportional to the 3 3. of the gas in accordance with 4 law. The solubility of a gas 4. decreases with increasing 5. A solution that contains the 5. maximum amount of solute at a given temperature is said to be Two liquids that are mutually soluble in each other are 7. said to be 7. Generally the 8 of a solid in water 8. 9 with increasing temperature, but there are exceptions. A(n) solution holds more solute than is theoretically possible. 10. Chapter 16 Solutions 399

2 Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 11. The rate at which a solute dissolves can be increased by grinding. 12. As the temperature of a solvent decreases, the solubility of a solute increases. 13. Stirring a solute when adding it to a solvent should increase the rate of its dissolving. 14. Henry s law states that the solubility of a gas in a liquid is a function of temperature. 15. Two liquids that dissolve in each other are miscible. Part C Matching Match each description in Column B to the correct term in Column A. Column A Column B 16. saturated solution 17. solubility a. the amount of a substance that dissolves in a given quantity of solvent at a given temperature b. The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. 18. unsaturated solution 19. miscible 20. immiscible 21. supersaturated solution 22. Henry s law Part D Problem c. solution that contains the maximum amount of solute for a given amount of solvent at a constant temperature d. a solution containing more solute than it can theoretically hold at a given temperature e. description of two liquids that dissolve in each other f. a solution that contains less solute than possible at a given temperature g. description of two liquids that do not dissolve in each other Solve the following problem in the space provided. Show your work. 23. The solubility of a gas in water is 1.6 g/l at 1.0 atm of pressure. What is the solubility of the same gas at 2.5 atm? Assume the temperature to be constant. 400 Core Teaching Resources

3 16.2 CONCENTRATIONS OF SOLUTIONS Section Review Objectives Solve problems involving the molarity of a solution Describe the effect of dilution on the total moles of solute in solution Define what is meant by percent by volume [%(v/v)] and percent by mass [%(m/m)] Vocabulary concentration dilute solution concentrated solution molarity (M) Key Equations moles of solute Molarity (M) l iters of solution M 1 V 1 M 2 V 2 volume of solute Percent by volume [%(v/v)] 100% volume of solution mass of solute Percent by mass [%(m/m)] 100% mass of solution Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. The relative amounts of solute and 1 in a 2 can 1. be described qualitatively as 3 or concentrated. Quantitative 2. units of concentration include molar concentration, percent by 3. volume, and percent by mass. 4. Molarity, the most important unit of concentration in 5. chemistry, is expressed as 4 of solute per 5 of solution. 6. Solutions of different concentrations can be prepared by 7. 6 a stock solution. In dilution, the moles of 7 remain 8. the same, while the amount of 8 changes. Chapter 16 Solutions 401

4 Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 9. One hundred ml of 1.0M sodium hydroxide solution is more concentrated than 1.0 L of 5M sodium hydroxide solution. 10. The amount of sodium hydroxide in 100 ml of 1.0M NaOH is less than that in 1.0 L of 5M NaOH solution. 11. Fifty ml of a 32% solution (v/v) of ethyl alcohol in water would contain 42 ml of water. 12. A dilute solution is a quantitative expression of concentration. Part C Matching Match each description in Column B to the correct term in Column A. Column A Column B 13. concentration 14. dilute solution 15. concentrated solution 16. molarity a. number of moles of solute dissolved in 1 L of solution b. measure of the amount of solute that is dissolved in a given quantity of solvent c. solution that contains a low concentration of solute d. concentration expressed as volume of solute over volume of solution 100% 17. percent solution Part D Problem Solve the following problem in the space provided. Show your work. 18. What mass of sucrose, C 12 H 22 O 11, is needed to make ml of a 0.50M solution? e. solution that contains a high concentration of solute 402 Core Teaching Resources

5 16.3 COLLIGATIVE PROPERTIES OF SOLUTIONS Section Review Objectives Identify the three colligative properties of solutions Describe why the vapor pressure, freezing point, and boiling point of a solution differ from those properties of the pure solvent. Vocabulary colligative properties freezing-point depression boiling-point elevation Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. In a solution, the effects of a nonvolatile 1 on the 1. properties of the solvent are called 2. They include 3 2. point and vapor pressure 4, and boiling point 5. In 3. each case, the magnitude of the effect is 6 proportional to 4. the number of solute molecules or ions present in the Colligative properties are a function of the number of solute 6. 8 in solution. For example, one mole of sodium chloride 7. produces 9 as many particles in solution as one mole of 8. sucrose and, thus, will depress the freezing point of water as much. 10. Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 11. When added to 1000 g of water, 2 moles of a solute will increase the boiling point by C. 12. One mole of solute A will depress the freezing point of 1000 g of water the same as one mole of solute B. Chapter 16 Solutions 403

6 13. Addition of a nonvolatile solute will lower the boiling point of a solvent. 14. Addition of a nonvolatile solute will lower the freezing point of a solvent. Part C Matching Match each description in Column B to the correct term in Column A. Column A Column B 15. colligative properties 16. freezing-point depression 17. boiling-point elevation 18. vapor pressure a. difference between the freezing point of a solution and the freezing point of the pure solvent b. pressure exerted by a vapor that is in equilibrium with its liquid in a closed system c. difference between the boiling point of a solution and the boiling point of the pure solvent d. properties of solutions that depend only on the number of particles in solution Part D Questions and Problems Answer the following questions in the space provided. 19. How many moles of solute particles are produced by adding one mole of each of the following to water? a. sodium nitrate b. glucose c. aluminum chloride d. potassium iodide 20. An equal number of moles of NaCl and K 2 CO 3 are dissolved in equal volumes of water. Which solution has the higher a. boiling point? b. vapor pressure? c. freezing point? 404 Core Teaching Resources

7 16.4 Section Review CALCULATIONS INVOLVING COLLIGATIVE PROPERTIES Objectives Calculate the molality and mole fraction of a solution Describe how the freezing-point depression and boiling-point elevation are related to molality Vocabulary molality (m) mole fraction Key Equations moles of solute Molality kilogram of solvent na mole fractions: X A na n B where n A moles of solute n B moles of solvent T b K b m T f K f m molal freezing-point depression constant (K f ) nb X B na n B molal boiling-point elevation constant (K b ) Part A Completion Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number. Molality is an expression of concentration involving the ratio 1. of 1 particles to 2 particles. Molality is expressed as 2. moles of solute per 3 of solvent. 3. Another expression of concentration is 4, in which 4. concentrations are expressed as the ratio of moles of solute to the 5. total number of moles of solvent and solute. Each solvent has a 6. characteristic 5 elevation constant and molal freezing-point 7. 6 constant. The elevation in boiling point of a solution can 8. be calculated by multiplying the 7 concentration of the solution by the boiling-point 8 constant of the solvent. Chapter 16 Solutions 405

8 Part B True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT. 9. It is possible to calculate the molar mass of a solute if you know the K b or K f of a solvent. 10. Molal concentration is the same as molar concentration. 11. The depression in freezing point of a solution is proportional to the molal concentration of solute. 12. The sum of X A and X B for any solution is always 1. Part C Matching Match each description in Column B to the correct term in Column A. Column A Column B 13. molality 14. mole fraction 15. molal freezing-point depression constant a. a constant for a given solvent equal to the change in boiling point for a 1m solution b. number of moles of solute dissolved in 1 kilogram of solvent c. mass of one mole of a substance 16. molal boiling-point elevation constant 17. molar mass Part D Problem d. a constant for a given solvent equal to the change in freezing point for a 1m solution e. ratio of moles of solute in solution to the total number of moles of solute and solvent Solve the following problem in the space provided. Show your work. 18. What is the freezing point of a solution that contains 2.0 mol of CaCl 2 in g of water? K f for water 1.86 C/m 406 Core Teaching Resources

9 16 SOLUTIONS Practice Problems In your notebook, solve the following problems. SECTION 16.1 PROPERTIES OF SOLUTIONS 1. The solubility of CO 2 in water at 1.22 atm is 0.54 g/l. What is the solubility of carbon dioxide at 1.86 atm? Assume that temperature is constant. 2. What mass of KCl will produce a saturated solution in g of water at 20 C? The solubility of KCl at 20 C is 34.0 g/100 g H 2 O. 3. A saturated solution of silver nitrate is prepared in g of water at 20 C. The solution is then heated to 50.0 C. How much more silver nitrate must now be added to obtain a saturated solution? (Use Table 16.1.) SECTION 16.2 CONCENTRATIONS OF SOLUTIONS 1. Calculate the molarity of each of the following solutions. a mol of NaCl dissolved in 1.6 L of solution b g of potassium nitrate, KNO 3, in enough water to make ml of solution 2. Calculate the number of grams of solute needed to prepare each of the following solutions. a ml of a 3.0M solution of potassium hydroxide, KOH b. 2.0 liters of 2.0M nitric acid, HNO 3, solution 3. What is the molarity of a solution that contains g of sodium nitrate (NaNO 3 ) in 3.0 liters of solution? 4. You must prepare ml of 0.750M NaBr solution using 2.00M NaBr stock solution. How many milliliters of stock solution should you use? 5. In order to dilute 1.0 L of a 6.00M solution of NaOH to 0.500M solution, how much water must you add? 6. What is the concentration in percent by volume, %(v/v), of the following solutions? a ml of methanol in a total volume of ml b ml of rubbing alcohol (C 3 H 7 OH) diluted to a volume of ml with water 7. How many grams of solute are needed to prepare each of the following solutions? a L of a 3.00% (m/m) NaCl solution? b L of 5.00% (m/m) KNO 3 solution? Chapter 16 Solutions 407

10 SECTION 16.3 COLLIGATIVE PROPERTIES OF SOLUTIONS 1. What are colligative properties of solutions? Give examples of three colligative properties. 2. How many particles in solution are produced by each formula unit of potassium carbonate, K 2 CO 3? 3. How may moles of particles would 3 mol Na 2 SO 4 give in solution? 4. What is the boiling point of a solution that contains 2 mol of magnesium chloride in g of water? 5. What kind of property is vapor-pressure lowering? 6. An equal number of moles of NaCl and CaCl 2 are dissolved in equal volumes of water. Which solution has the lower a. freezing point? b. vapor pressure? c. boiling point? SECTION 16.4 CALCULATIONS INVOLVING COLLIGATIVE PROPERTIES 1. Calculate the mole fraction of solute in each of the following solutions. a. 3.0 moles of lithium bromide, LiBr, dissolved in 6.0 moles of water b g of potassium nitrate, KNO 3, dissolved in g of water 2. How many grams of sodium chloride must dissolve in g of water to make a 0.50 molal solution? 3. How many grams of lithium sulfide must be dissolved in g of water to make a 2.0 molal solution? 4. Find the molality of each of the following solutions. a. 2.3 moles of glucose dissolved in g of water b. 131 g of Ba(NO 3 ) 2 dissolved in g of water 5. Find the boiling points of the following solutions. a. 2.00m solution of sodium chloride, NaCl b. 1.50m solution of calcium chloride, CaCl 2 6. Find the freezing points of the following solutions. a moles of sodium chloride, NaCl, dissolved in g of water b g of table sugar, C 12 H 22 O 11, dissolved in g of water 408 Core Teaching Resources

11 16 INTERPRETING GRAPHICS Use with Section 16.1 Solubilities of Some Substances in Water at Various Temperatures Solubility (g/100 g of H 2 O) Substance Formula 0 C 20 C 50 C 100 C Barium hydroxide Ba(OH) Barium sulfate BaSO Calcium hydroxide Ca(OH) Lead(II) chloride PbCl Lithium carbonate Li 2 CO Potassium chlorate KClO Potassium chloride KCl Sodium chloride NaCl Sodium nitrate NaNO Sodium sulfate Na 2 SO Silver nitrate AgNO Lithium bromide LiBr Cane sugar (sucrose) C 12 H 22 O A portion of Table 16.1 from your textbook has been reproduced above. Use the table to answer the following questions. 1. Saturated solutions of each of the following compounds are made at 20 C. Circle the letter(s) of the solution(s) that will form a precipitate upon heating. a. NaCl c. Li 2 CO 3 b. Na 2 SO 4 d. sucrose 2. A saturated solution of potassium chloride is prepared in g of water at 20 C. If the solution is heated to 50 C, how much more KCl must be added to obtain a saturated solution? Chapter 16 Solutions 409

12 3. A saturated solution of sucrose in g of boiling water is cooled to 20 C. What mass of rock candy will be formed? 4. Using data from the table, plot the solubility curves of KCl, LiBr and Na 2 SO 4 on the graph below. Be sure to label each curve. Use the graph to answer the following questions. Concentration (g/100 g H 2 O) Temperature C a. Which of the compounds is most soluble at 25 C? b. Which of the compounds has the lowest solubility at 90 C? 410 Core Teaching Resources

13 16 VOCABULARY REVIEW From each group of terms, choose the term that does not belong and then explain your choice. 1. saturated, unsaturated, molarity, supersaturated 2. miscible, immiscible, concentration 3. molarity, mole fraction, molality, Henry s law 4. solubility of a gas, Henry s law, pressure, colligative properties 5. colligative properties, saturated solution, freezing-point depression, molality 6. molal freezing-point depression constant (K f ), colligative properties, ice cream, molarity 7. surface area, mole fraction, temperature, stirring 8. dilute solution, concentrated solution, M 1 V 1 M 2 V 2, boiling-point elevation Chapter 16 Solutions 411

14 16 SOLUTIONS Chapter Quiz Choose the best answer and write its letter on the line. 1. At a given temperature, the solubility of a gas in a liquid is: 16.1 a. proportional to the square root of the pressure of the gas above the liquid. b. directly proportional to the pressure of the gas above the liquid. c. inversely proportional to the pressure of the gas above the liquid. d. unrelated to the pressure of the gas above the liquid. 2. If the addition of a crystal to an aqueous solution causes a great deal of 16.1 dissolved solid to come out of solution, the original solution was: a. a colloid. c. saturated. b. unsaturated. d. supersaturated. 3. In general, as the temperature of a solution composed of a gas in a 16.1 liquid is decreased, the solubility of the gas: a. increases. c. remains the same. b. decreases. d. none of the above 4. What is the molarity of a solution that contains 8 moles of solute in L of solution? a. 4M c. 6M b. 8M d. 0.25M 5. To 225 ml of a 0.80M solution of KI, a student adds enough water to 16.2 make 1 L of a more dilute KI solution. What is the molarity of the new solution? a. 180M c. 137 g b. 0.18M d. 100 g 6. How many milliliters of alcohol are in 167 ml of an 85.0% (v/v) alcohol 16.2 solution? a. 252 ml c. 142 ml b. 228 ml d. 145 ml 7. Colligative properties depend on: 16.3 a. the nature of the solute. b. the nature of the solvent. c. the number of particles dissolved in a given mass of solvent. d. none of the above 8. What is the freezing point of an aqueous 0.500m NaBr solution? 16.4 (K f for water = 1.86 C/m) a C c C b C d C 412 Core Teaching Resources

15 16 SOLUTIONS Chapter Test A A. Matching Match each description in Column B to the correct term in Column A. Write the letter of the correct description on the line. Column A Column B saturated solution colligative properties miscible molarity unsaturated solution a. At a given temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. b. a solution containing the maximum amount of solute that can be dissolved at a given temperature c. the number of moles of solute dissolved in 1 L of solution d. describes liquids that are insoluble in each other e. contains only a small amount of the maximum amount of solute that can be dissolved at a given temperature immiscible concentrated solution Henry s law supersaturated solution dilute solution B. Multiple Choice Choose the best answer and write its letter on the line. f. contains less solute than can theoretically be dissolved g. describes liquids that dissolve in each other h. contains more solute than can theoretically be held at a given temperature i. depend upon the number of particles of solute in solution j. a solution with a large amount of solute compared to solvent 11. Increasing the temperature of a liquid solid solution will: a. always increase the rate at which a crystalline solute dissolves. b. often increase the amount of crystalline solute that dissolves. c. both a and b d. neither a nor b Chapter 16 Solutions 413

16 12. Which of the following operations usually makes a substance dissolve faster in a solvent? a. agitation c. crushing the substance to a powder b. raising the temperature d. all of the above 13. To increase the solubility of a gas at constant temperature and 202 kpa pressure from 0.85 g/l to 5.1 g/l, the pressure would have to be increased to: a kpa. c. 606 kpa. b. 505 kpa. d kpa. 14. If the pressure of a gas above a liquid is decreased (at constant temperature), the solubility of the gas in the liquid: a. remains unchanged. b. increases. c. decreases. d. would change but in an unpredictable direction. 15. An ionic compound has a solubility of 30 g per 100 ml of water at room temperature. A solution containing 70 g of the compound in 250 ml of water at the same temperature is: a. saturated. c. unsaturated. b. supersaturated. d. a suspension. 16. How many ml of alcohol are in 240 ml of 95.0% (v/v) alcohol solution? a. 12 ml c. 145 ml b. 228 ml d. 142 ml 17. If more solvent is added to a solution: a. the molarity decreases. b. the solution becomes less dilute. c. the percent (v/v) increases. d. all of the above 18. What is the molarity of a 200-mL solution in which 0.2 mole of sodium bromide is dissolved? a. 0.20M c. 0.40M b. 1.0M d. 4.0M 19. What is the percent (m/m) of a water solution that contains 60 g of calcium chloride, CaCl 2, and that has a mass of 400 g? a. 15% c. 24% b. 1.35% d. 6.7% 20. Which of the following is not a colligative property of a solution? a. boiling-point elevation c. vapor-pressure lowering b. solubility d. freezing-point depression 414 Core Teaching Resources

17 21. If one mole of each of these solutes is added to the same amount of water, which solution has the highest boiling point? a. copper(ii) chloride, CuCl 2 b. glucose, C 6 H 12 O 6 c. magnesium acetate, Mg(C 2 H 3 O 2 ) 2 d. aluminum sulfate, Al 2 (SO 4 ) 3 C. True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true NT. 22. The solubility of a solute can be increased by cooling the solvent. 23. Grinding a solute increases the rate at which it dissolves. 24. As an open bottle of a carbonated beverage warms, the concentration of dissolved carbon dioxide decreases. 25. One hundred ml of a 5.0M sodium chloride solution is more concentrated than 1.0 L of a 1.0M sodium chloride solution. 26. The amount of sodium chloride in 100 ml of a 5.0M NaCl solution is greater than that in 1.0 L of a 1.0M NaCl solution. 27. As the temperature of a solvent increases, the solubility of a gaseous solute increases. 28. Fifty ml of a 16% solution (v/v) of ethyl alcohol in water contains 16 ml of water. 29. An unsaturated solution contains less solute than required for equilibrium. 30. A saturated solution has a large amount of solute compared to solvent. 31. If a crystal of a substance dissolves when added to an aqueous solution, the original solution containing that substance was supersaturated. D. Problems Solve the following problems in the space provided. Show your work. 32. How would you prepare 250 ml of 0.60M Al 2 (SO 4 ) 3 solution from a 2.0M Al 2 (SO 4 ) 3 stock solution? Chapter 16 Solutions 415

18 33. Calculate the molarity of a solution prepared by dissolving 95.5 g of KNO 3 in enough water to make 750 ml of solution. 34. A gas has a solubility in water of 16.9 g/l at 15 C and 505 kpa of pressure. What is its solubility in water at 15 C and 606 kpa of pressure? E. Essay Write a short essay for the following. 35. Explain on a particle basis how the addition of a solute affects the boiling point, freezing point, and vapor pressure of the solvent. 416 Core Teaching Resources

19 F. Additional Problems Solve the following problems in the space provided. Show your work. 36. Calculate the boiling point of a solution that contains mol of K 3 PO 4 dissolved in 2750 g of water. (K b for water = C/m.) 37. Calculate the molality of a solution prepared by dissolving 175 g of KNO 3 in 1250 g of water. Chapter 16 Solutions 417

20 16 SOLUTIONS Chapter Test B A. Matching Match each term in Column B to the correct description in Column A. Write the letter of the correct term on the line. Column A Column B 1. the number of moles of a solute dissolved in 1 L of solution a. colligative properties 2. the difference in temperature between the boiling points of a solution and of the pure solvent b. Henry s law 3. describes two liquids that dissolve in each other c. boiling-point elevation 4. the number of moles of solute dissolved in 1 kg of solvent d. supersaturated solution 5. a solution that contains more solute than it can theoretically hold at a given temperature e. molality those properties of solutions that depend on the number of particles dissolved in a given mass of solvent a solution that contains the maximum amount of solute for a given amount of solvent at constant temperature the difference in temperature between the freezing points of a solution and of the pure solvent a measure of the amount of solute that is dissolved in a given quantity of solvent At a given temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid. f. saturated solution g. molarity h. miscible i. freezing-point depression j. concentration 418 Core Teaching Resources

21 B. Multiple Choice Choose the best answer and write its letter on the line. 11. The rate at which a solute dissolves in a given solvent is determined by: a. the extent to which the solution is agitated. b. the temperature of the solution. c. the size of the solute particles. d. all of the above 12. A glass of iced tea containing excess sugar at the bottom is said to be: a. saturated. c. supersaturated. b. unsaturated. d. homogeneous. 13. If the solubility of AgNO 3 at 40 C is 311 g per 100 g of water, what mass of this solute can be dissolved in 350 g of water at the same temperature? a g c. 1.1 g b g d g 14. In general, as the temperature of a solvent increases, the solubility of any gas dissolved in that solvent: a. increases. c. remains the same. b. decreases. d. cannot be predicted. 15. Which of the following would increase the solubility of a gas in a liquid? a. stirring the solution b. increasing the temperature of the solvent c. increasing the pressure of the gas above the solution d. adding more solvent 16. If the solubility of a gas in water is 1.22 g/l at 2.75 atm, what is its solubility (in g/l) at 1.0 atm? a g/l c g/l b g/l d g/l 17. The most concentrated solution from among those listed is: a. 100 ml 0.25M KCl. c. 75 ml 0.23M KNO 3. b. 150 ml 0.18M NaOH. d. 200 ml 0.15M NaNO The molarity of a solution that contains 14 g KOH per 150 ml of solution is: a. 93M. c M. b. 1.7M. d. 11M. 19. How many moles of solute are present in 1.25 L of a 0.75M NaNO 3 solution? a. 1.7 mol c mol b mol d mol 20. What volume of 1.25M HCl would be required to prepare 180 ml of a 0.500M HCl solution? a. 450 ml c ml b. 72 ml d ml Chapter 16 Solutions 419

22 21. What is the percent (m/m) of a solution containing 25 g of NaCl in 175 g of solution? a. 700% c. 7.0% b. 0.14% d. 14% 22. Which of the following results from the presence of a solute in a given solvent? a. The vapor pressure of the solution is lower than that of the pure solvent. b. The boiling point of the solution is lower than that of the pure solvent. c. The freezing point of the solution is higher than that of the pure solvent. d. all of the above 23. What is the molality of a solution prepared by dissolving 13.0 g of Ba(NO 3 ) 2 in 450 g of water? a molal c molal b. 29 molal d molal 24. The mole fraction of ethanol in a solution containing 1.50 moles of ethanol and 3.25 mol of water is: a c b d The addition of antifreeze to water in a car radiator causes the freezing point of the mixture to: a. increase. c. remain the same. b. decrease. d. vary unpredictably. 26. What is the molality of an aqueous solution of a molecular solute if the boiling point of the solution is C? a molal c molal b molal d molal C. True-False Classify each of these statements as always true, AT; sometimes true, ST; or never true NT. 27. Whether a solute dissolves in a given solvent is determined by the nature of the two substances. 28. Stirring a solution at constant temperature increases the amount of solute that can be dissolved. 29. At constant temperature, more powdered sugar will dissolve in a cup of coffee than will sugar that is in the form of cubes. 30. Oil and water are completely miscible. 31. Increasing the temperature increases the solubility of a given substance. 420 Core Teaching Resources

23 32. A 2.5M solution of KNO 3 contains 2.5 moles solute particles per 1 kg of solvent. 33. The number of moles of solute in a given solution decreases as the solution is diluted. 34. A solution has a lower vapor pressure than that of the pure solvent. 35. The boiling point of a solution is lower than that of the pure solvent. 36. The freezing point of a 1.0 molal solution of MgCl 2 is 5.58 C lower than that of pure water. D. Problems Solve the following problems in the space provided. Show your work. 37. If a saturated solution of AgNO 3 at 20 C contains 216 g AgNO 3 per g of water, what mass of water could contain 725 g of this solute at the same temperature? 38. At 10 C, the solubility of a gas in water is 2.45 g/l at atm. What pressure would be required to produce an aqueous solution containing 6.25 g/l of this gas at 10 C? 39. Calculate the molarity of a solution that contains 50.0 g of Mg(NO 3 ) 2 per 225 ml of solution. 40. What mass of AgNO 3 would be required to prepare a molal solution in 125 g of water? Chapter 16 Solutions 421

24 E. Essay Write a short essay for the following 41. Often during the winter, salt is sprinkled on bridges and sidewalks. Explain the purpose for doing so and the reasons why salt is effective for this purpose. F. Additional Problems Solve the following problems in the space provided. Show your work. 42. What mass of H 2 SO 4 would be required to prepare 750 ml of a 0.15M H 2 SO 4 solution? 43. Determine the freezing point of a solution made by adding 27.5 g of methanol (CH 3 OH) to g of water. 422 Core Teaching Resources

25 44. What is the boiling point of an aqueous solution that contains 62.5 g of Ba(NO 3 ) 2 in g of water? Chapter 16 Solutions 423