Review 8: Solutions

AP chem Text: chapter 11 • • • • Review - 8 (Solutions) M = mol/L m = mol/kg χa = na/nT o Psoln = χsolvP solv (nonvolatile solute) PROBLEMS 1. A solution is prepared by dissolving 1.25 g of an unknown substance in 100.0 mL of water. Which procedure could be used to find if the solute is an electrolyte? a. Measure the specific heat of the solution. b. Measure the volume of the solution. c. Measure the freezing point of the solution. d. Determine the specific heat of the solution. e. Determine the volume of the solute. 2. 3. • • • Strontium sulfate will precipitate when a solution of sodium sulfate is added to a strontium nitrate solution. What will be the strontium 2+ ion, Sr , concentration remaining after 30.0 mL fo a 0.10 M Na2SO4 solution are added to 70.0 mL of 0.20 M Sr(NO3)2 solution? a. 0.14 M b. 0.15 M c. 0.11 M d. 0.20 M e. 0.030 M 4. Which is a strong electrolyte? a. HNO2(aq) b. KNO3(aq) c. C2H5OH(aq) d. CH3COOH(aq) e. NH3(aq) 5. A solution with a total chloride ion, Cl , concentration of 1.0 M is needed. Initially, the solution is 0.30 M in MgCl2. How many moles of solid CaCl2 must be added to 400 mL of the MgCl2 solution to yield the desired concentration of chloride? a. 0.10 b. 0.080 c. 0.20 d. 0.15 e. 0.16 Psoln = χaP ΔT = iKm π = iMRT o a + χ bP 6. Assuming the volumes are additive, + what is the final H concentration after mixing 30.0 mL of 0.50 M HNO3 with 70.0 mL of 1.00 M HCl? a. 0.75 M b. 1.50 M c. 1.25 M d. 0.85 M e. 0.43 M 7. The molality of a 1.0-M ethyl alcohol solution may be determined if which of the following is supplied? a. density of solution b. van’t Hoff factor for ethyl alcohol c. temperature of the solution d. volume of the solution e. solubility of ethyl alcohol + What is the final [K ] in a solution made by mixing 300 mL of 1.0 M KNO3 and 700 mL of 2.0 M K3PO4? a. 1.5 M b. 5.0 M c. 3.0 M d. 2.0 M e. 4.5 M Name: ____________________ 8. 9. A solution of chloroform, CHCl3, in carbon tetrachloride, CCl4, is nearly ideal. The vapor pressure of o chloroform is 170 mmHg at 20 C, and the vapor pressure of carbon tetrachloride is 87 mmHg at this temperature. What is the mole fraction of carbon tetrachloride in the vapor over an equimolar solution of these two liquids? a. 0.25 b. 0.87 c. 0.66 d. 0.50 e. 0.34 To prepare 3.0 L of a 0.20 M K3PO4 solution (MW = 212), a student should follow which of the following procedures? a. The student should weigh 42 g of solute and add sufficient water to obtain a final volume of 3.0 L. b. The student should weigh out 42 g of solute and add 3.0 kg of water. c. The student should weigh 130 g of solute and add sufficient water to obtain a final volume of 3.0 L. d. The student should weigh 42 g of solute and add 3.0 L of water. e. The student should weigh 130 g of solute and add 3.0 L of water. o b (volatile solute) 10. A 5.2 m solution of CH3OH(aq) is supplied. What is the mole fraction of methyl alcohol in this solution? a. 0.10 b. 0.19 c. 0.086 d. 0.050 e. 0.094 11. Which has the highest boiling pt? a. 0.10 M HI(aq) b. 0.10 M (NH4)3PO4(aq) c. 0.20 M C2H5OH(aq) d. 0.10 M NH4Cl(aq) e. 0.10 M NaI(aq) 12. How many grams of MgSO4 are in 100.0 mL of a 5.0 M solution? a. 600 g b. 5.0 g c. 12 g d. 60.0 g e. 120 g 13. How many mL of concentrated nitric acid (16.0 M HNO3) are needed to prepare 0.500 L of 6.0 M HNO3? a. 0.19 mL b. 250 mL c. 375 mL d. 190 mL e. 100 mL 14. When using the freezing-point depression method to find the molar mass of a nonelectrolyte, what is needed in addition to the following? ž the freezing point constant, Kf ž the freezing point of pure solvent ž the freezing point of the solution a. the mass of the solute b. the volume of the solvent and the mass of the solute c. the mass of the solvent and the boiling point of the solvent d. the mass of the solvent and the mass of the solute e. no more information is needed 15. A solution has a mole fraction of 0.20 of CHCl3 in CCl4. What is the molality of chloroform? a. 1.7 m b. 0.17 m c. 0.20 m d. 1.3 m e. 1.20 m © S. O’Malley 2012 16. A solution is 10% urea by mass. Which item(s) are needed to find the molarity of this solution? i. the density of the solution ii. the density of the solvent iii. the molecular weight of urea a. i and iii b. i only c. ii only d. iii only e. i and ii 17. Which of the following solutions has the greatest ΔTf? a. 0.10 m (NH4)2SO4(aq) b. 0.10 m MnSO4(aq) c. 0.10 m NaF(aq) d. 0.10 m KCl(aq) e. 0.10 m CH3OH(aq) 18. Which solution has the greatest conductivity? a. 0.2 M NaOH b. 0.2 M RbCl2 c. 0.2 M NH4NO3 d. e. 0.2 M HNO2 0.2 M K3PO4 19. An aqueous solution of KNO3 is o o cooled from 75 C to 15 C. Which statement is true? a. The molarity of the solution does not change. b. The molality of the solution decreases. c. The density of the solution does not change. d. The molality of the solution does not change. e. The mole fraction of the solute increases. 20. How many milliliters of water must be added to 50.0 mL of 10.0 M HNO3 to prepare 4.00 M HNO3? a. 50.0 mL b. 125 mL c. 500 mL d. 250 mL e. 75.0 mL 21. Pick the pair of substances that will most likely obey Raoult’s law. a. CH3CH2CH2CH2COOH and C5H12 b. C5H12 and H2O c. CH3CH2CH2CH2COOH and H 2O d. H3PO4 and H2O e. C5H12 and C6H14 22. The best method to isolate pure MgSO4 from MgSO4(aq) is a. Evaporate the solution to dryness. b. Titrate the solution. c. Electrolyze the solution. d. Use paper chromatography. e. Filter the solution. 23. Which conditions yield the highest concentration of N2(g) in water? o a. Pgas = 1.0 atm, T = 25 C o b. Pgas = 0.5 atm, T = 55 C o c. Pgas = 2.0 atm, T = 25 C o d. Pgas = 2.0 atm, T = 85 C o e. Pgas = 1.0 atm, T = 85 C FREE-RESPONSE o 24. Five beakers each containing 100.0 mL of an aqueous solution are placed on a lab bench. The solutions are all at 25 C. • Solution 1 contains 0.20 M KNO3. • Solution 2 contains 0.10 M BaCl2. • Solution 3 contains 0.15 M C2H4(OH)2. • Solution 4 contains 0.20 M (NH4)2SO4. • Solution 5 contains 0.25 M KMnO4. a. One of the solutions could oxidize two of the other solutions. Which solution is it? Which solutions could it oxidize? b. Which solution has the lowest pH? Explain. c. Which pair of solutions would give a precipitate if they are mixed? What is the formula for this precipitate? d. Which solution would be the poorest conductor of electricity? Explain. e. Rank the solutions in order of increasing boiling point. Explain. o 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. C E C B B D A E C C B D D D A A A E D E E A C 25. Five beakers at 25 C are placed in a row on a countertop. Each beaker is half filled with a 0.20 M aqueous solution. The solutes, in order, are: (1) potassium sulfate (2) methyl alcohol (3) sodium carbonate (4) ammonium chromate (5) barium chloride. a. Which solution will form a precipitate when ammonium chromate is added to it? Give the formula of the precipitate. b. Which solution is the most basic? Explain. c. Which solution will exhibit the lowest boiling point elevation? Explain. d. Which solution is colored? e. Which of the other solutions will not react with solution (5)? Problems taken from “5 Steps to a 5”, McGraw Hill 24. a. solution 5, solutions 2 and 3 b. solution 4, NH4+ is a weak acid and undergoes hydrolysis c. solutions 2 and 4, BaSO4 d. solution 3, it is a non-electrolyte e. 3 < 2 < 1 < 5 < 4; number of particles increases 25. a. (5), BaCrO4 b. (3), Na2CO3 is a basic salt in solution c. (2), CH3OH is a non-electrolyte and does not dissociate d. (4), (NH4)2CrO4 is yellow e. (2), CH3OH will not react with BaCl2