Sample Test 1 SAMPLE TEST 1. CHAPTER 12

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1 13 Sample Test 1 SAMPLE TEST 1. CHAPTER The molality of a solution is defined as a. moles of solute per liter of solution. b. grams of solute per liter of solution. c. moles of solute per kilogram of solution. d. moles of solute per kilogram of solvent. e. the gram molecular weight of solute per kilogram of solvent. > d moles of solute per kilogram of solvent. 2. What is the molarity of a NH 3 solution which contains 4.25 g of NH 3 in 2.00 L of solution? a M b M c M d M e M > a M 3. What is the percent NaCl by mass in a 1.00 molal aqueous solution? a b c d e > a How many moles of ethanol, must be dissolved in one hundred grams of water to give a 1.5 molal solution? a. 15 b. 1.5 c d e > c When one mole of a nonvolatile nonelectrolyte is dissolved in three moles of a solvent, the vapor pressure of the solution compared to that of the pure solvent is a. 1/4. b. 1/3. c. 1/2. d. 2/3. e. 3/4. > e 3/4. 6. Using Raoult's law, given that the pure vapor pressure of water (M.W g/mol) at 75oC is 290mmHg, the vapor pressure of an aqueous solution at 75oC containing 60g of urea (M.W g/mol), a nonelectrolyte, in 180g of water is a. 29 mmhg. b. 100 mmhg. c. 130 mmhg. d. 190 mmhg. e. 264 mmhg. > e 264 mmhg. 7. According to Henry's Law, the concentration of a gas in solution at a constant temperature is directly proportional to a. the pressure of the gas above the solution. b. the vapor pressure of the pure solvent. c. the mole fraction of solvent present. d. Each of these statements is true. > a the pressure of the gas above the solution. 8. A 60.0-g sample of NaOH ( F.W g/mol) is dissolved in water, and the solution is diluted to give a final volume of 3.00 L. The molarity of the final solution is

2 a M. b M. c M. d M. e M. > a M. 9. How many grams of Na 2 SO 4 (F.W. 142 g/mol) are contained in L of M Na 2 SO 4 solution? a b c d e > a Using Raoult's law, given that the pure vapor pressure of water (M.W g/mol) at 75oC is 290mmHg, the vapor pressure of an aqueous solution at 75oC containing 60g of urea (M.W g/mol), a nonelectrilyte, in 180g of water is a. 29 mmhg. b. 100 mmhg. c. 130 mmhg. d. 190 mmhg. e. 264 mmhg. > e 264 mmhg. 11. The solubility of a gas in a liquid can always be increased by a. increasing the temperature of the solvent. b. decreasing the polarity of the solvent. c. decreasing the temperature of the gas above the solvent. d. decreasing the pressure of the gas above the solvent. e. increasing the pressure of the gas above the solvent. > e increasing the pressure of the gas above the solvent. 12. Which one of the following is not a colligative property? a. osmotic pressure. b. boiling point elevation. c. density d. vapor pressre lowering. e. freezing-point depression > c density 13. If mol of napthalene is dissolved in g of benzene (C 6 H 6 ), what is the molality? a b c d e > c What is the mole fraction of methanol, CH 3 OH (M.W. 32 g/mol), in an ethanol, C 2 H 5 OH (M.W. 46 g/mol), solution that is 60.0% ethanol by mass? a b c d e > c What is the molality of ethyl alcohol, C 2 H 5 OH (M.W g/mol), in an aqueous solution that is 50.0% ethyl alcohol by mass? a b c d e

3 > b Which of the following solutions made up of soluble salts has the highest osmotic pressure? a M NaCl b M CaCl 2 c M Ba(NO 3 ) 2 d M Al(NO 3 ) 3 > c 0.15 M Ba(NO 3 ) Calculate the MOLALITY of C 2 H 5 OH in a water solution which is prepared by mixing 50.0 ml of C 2 H 5 OH with ml of H 2 O at 20 C. The density of the C 2 H 5 OH is g/ml at 20 C. a m b m c m d m e. none of these 18. A solution of two liquids, A and B, shows negative deviation from Raoult's Law. This means that a. the molecules of A interact strongly with other A-type molecules. b. the two liquids have a positive heat of solution. c. molecules of A interact weakly, if at all, with B molecules. d. the molecules of A hinder the strong interaction between B molecules. e. molecules of A interact more strongly with B than A with A or B with B. 19. Which of the following is NOT a colligative property? a. freezing point depression b. boiling point elevation c. osmotic pressure d. solubility e. two of the above 20. The molal freezing point depression constants for benzene and water are 5.12 and 1.86 respectively. When 4.6 g of formic acid (HCOOH) is dissolved in 1.0 kg of benzene, the observed freezing point lowering is 0.26C. When the same amount of formic acid is dissolved in 1.0 kg of water, the freezing point is lowered by 0.19C. To explain these results, we must assume that: a. formic acid is ASSOCIATED in benzene and MONOMERIC in water. b. formic acid is MONOMERIC in benzene and DISSOCIATED in water. c. formic acid is MONOMERIC in benzene and ASSOCIATED in water. d. formic acid is DISSOCIATED in benzene and MONOMERIC in water. e. none of these is true. 21. When one mole of a nonvolatile non-dissociating substance is dissolved in two moles of solvent, the ratio of the vapor pressure of the solution to that of the pure solvent (at the same temperature) is approximately: a. 1/3 b. 1/2 c. 2/3 d. 3/2 e. none of these 22. How many grams of water are needed to give a 3.00 m NH 3 solution if 15 moles of NH 3 are to be dissolved in the water? a. 5 b c. 4.5 d e Determine the molarity of a 25.0% CaCl 2 solution that has a density of g/ml. a b c d e What is the MOLALITY of a solution of 50.0 g of propanol (molar mass = 60.1 g/mol) in 152 ml water, if the density of water is 1.0 g/ml? a) 5.47 m b) m c) m d) m e) none of these 25. How many grams of C 12 H 22 O 11 are needed to dissolve in 250g of water to give a x 10-1 m solution? (M.W. C 12 H 22 O 11 = ) a g b g c g d g e. 1600g 15

4 A solution is made by adding mole of ethyl ether to mole of ethyl alcohol. If the vapor pressures of ethyl ether and ethyl alcohol at 20 o C are 375 torr and 20.0 torr, respectively, the vapor pressure of the solution at 20 o C (assuming ideal behavior) is: a) 79.2 torr b) 316 torr c) 47.5 torr d) 395 torr e) none of these 27. The term "proof" is defined as twice the percent by volume of pure ethanol in solution. Thus, a solution that is 95% (by VOLUME) ethanol is 190 proof. What is the MOLARITY of ethanol in a 92 proof ethanol/water solution? density of ethanol = 0.80 g/cm3 density of water = 1.0 g/cm3 mol. wt. of ethanol = 46 a) 0.46 M b) 0.80 M c) 0.92 M d) 8.0 M e) 17 M 28. Vapor pressure (in torr) at 25 o C benzene (C 6 H 6 ) 94.4 chloroform (CH 3 Cl) Using the above data, calculate the total vapor pressure of a chloroform-benzene solution at 25 o C which contains 50.0 g CH 3 Cl and 50.0 g C 6 H 6. Assume the solution behaves ideally. a) 67.8 torr b) 125 torr c) 141 torr d) 172 torr e) none of these 29. When a nonvolatile solute is added to a volatile solvent, the solution vapor pressure, the boiling point, the freezing point, and the osmotic pressure across a semipermeable membrane. a) decreases, increases, decreases, decreases. b) increases, increases, decreases, increases. c) increases, decreases, increases, decreases. d) decreases, decreases, increases, decreases. e) decreases, increases, decreases, increases. 30. A solute added to a solvent raises the boiling point of the solution because a) the temperature to cause boiling must be great enough to boil not only the solvent but also the solute. b) the solute particles lower the solvent's vapor pressure thus requiring a higher temperature to cause boiling. c) the solute particles raise the solvent's vapor pressure thus requiring a higher temperature to cause boiling. d) the solute increases the volume of the solution, and an increase in volume requires an increase in the temperature to reach the boiling point (derived from PV = nrt). e) two of the above are correct. 31. At a given temperature the vapor pressures of pure liquid benzene and toluene are 745 torr and 290 torr, respectively. A solution prepared by mixing benzene and toluene obeys Raoult's law. At this temperature the vapor pressure of benzene over a solution in which the mole fraction of benzene is equal to is a) 417 torr b) 352 torr c) 98.6 torr d) 253 torr e) none of these 32. A solution of hydrogen peroxide is 30.0% H 2 O 2 by mass and has a density of 1.11 g/cm 3. The MOLARITY of the solution is: a) 7.94 M b) 8.82 M c) 9.79 M d) e) none of these 33. A solution containing g of Mg(NO 3 ) 2 per liter has a density of g/ml. The MOLARITY of the solution is: a) M b) M c) M d) M e) none of these 34. The osmotic pressure, in torr, of a M solution of NaCl in water at 25C is APPROXIMATELY:

5 17 a) b) 15.6 c) 372 d) 186 e) none of these 35. When 100. ml of M HCl is diluted to 250. ml, the resulting MOLARITY of the HCl solution is: a) M b) M c) M d) M e) none of these 36. When 1.50 g of glutamic acid is dissolved in g H 2 O, the resulting solution freezes at C. (K f for H 2 O is 1.86C kg/mol.) The molecular weight of glutamic acid is: a) 14.7 g/mol b) 1.50 g/mol c) 189 g/mol d) 28.0 g/mol e) 147 g/mol 37. Benzene and toluene form an ideal solution. At 298K, what is the mole fraction of benzene in the liquid that is in equilibrium with a vapor that has equal partial pressures of benzene and toluene? At 298K, the vapor pressures of pure benzene and pure toluene are 95 and 28 torr, respectively. a) 0.50 b) 0.77 c) 0.23 d) 0.30 e) none of these 38. In order to calculate the freezing point of an ideal dilute solution of a single, non-dissociating solute in a solvent, the minimum information one must know is: a) the molality (of the solute). b) the molality (of the solute) and the freezing point depression constant of the solvent. c) the same quantities as in (b) plus the freezing point of the pure solvent. d) all of the quantities in (c) plus the molecular weight of the solute. e) all of the quantities in (c) plus the weight of the solvent. 39. The vapor pressure of water at 90C is atm. What is the vapor pressure (in atm) of a solution made by dissolving 1.00 mole of CsF(s) in 1.00 kg of water? Assume that Raoult's law applies. a) atm b) atm c) atm d) atm e) none of these 40. Pentane and hexane form an ideal solution. The components have the following properties: - - molar mass - density - bp - vapor pressure at 25 o C pentane g/ml 36 o C 511 torr hexane g/ml 69 o C 150 torr What is the mole fraction of pentane (X pentane ) in the vapor in equilibrium at 25C with a pentane-hexane solution in which X pentane = 0.30? a) X pentane = 0.23 b) X pentane = 0.29 c) X pentane = 0.59 d) X pentane = 0.68 e) X pentane = What is the mole fraction of ethanol, C 2 H 5 OH, in a methanol solution that is 40.%(w/w) methanol, CH 3 OH, by mass? a b c d Answers to questions: 1. > d moles of solute per kilogram of solvent. 2. > a M 3. > a > c > e 3/4. 6. > e 264 mmhg. 7. > a the pressure of the gas above the solution. 8. > a M. 9. > a > e 264 mmhg. 11. > e increasing the pressure of the gas above the solvent. 12. > c density 13. > c 1.00

6 14. > c > b > c 0.15 M Ba(NO 3 ) > d 8.56 m > e molecules of A interact more strongly with B than A with A or B with B > e solubility > a formic acid is ASSOCIATED in benzene and MONOMERIC in water > c 2/ > e a d g 26. a) 79.2 torr 27. >d) 8.0 M 28. >b) 141 torr 29. >e) decreases, increases, decreases, increases. 30. b) the solute particles lower the solvent's vapor pressure thus requiring a higher temperature to cause boiling. 31. d) 253 torr 32. c) 9.79 M 33. a) M 34. c) c) M 36. e) 147 g/mol 37. c) c) the same quantities as in (b) plus the freezing point of the pure solvent. 39. c) atm 40. c) X pentane = c