Chemistry Chapter 12 Solutions Part 2

1. A pure substance differs from a solution in the fact that a pure substance: a) exhibits no settling out. b) can be solid, liquid or gas, but a solution is a liquid. c) is a homogeneous mixture, while a solution is not. d) has a fixed composition. 2. The formation of a solution is FAVORED by which of the following factors? I. liberation of thermal energy in the solution process II. increase in the disorder or randomness of the system III. strong solvent-solvent interactions a) I, II and III b) I and II, but not III c) I only d) II only e) II and III, but not I 3. The insolubility of BaSO4 salt in water can be attributed PRIMARILY to: a) the large crystal lattice energy of the salt. b) very weak interactions between Ba2+ and SO42- ions with water molecules. c) very strong interactions between water molecules. d) the decrease in entropy of forming this solution. 4. Magnitudes of crystal lattice energy holding the lattice together generally: I. increase with increasing charge on the ions. II. increase with increasing size of the ions. a) I and II are both true b) neither I or II are true c) only I is true d) only II is true 5. Why did the white bear dissolve in water? a) Because she was a polar bear. b) Because she was white. c) Because bears always dissolve in water. d) To get to the other side. 6. Which gaseous substance would have the highest solubility in water? a) CO2 b) NH3 c) O2 d) none have appreciable solubility 7. Which substance would have the highest solubility in benzene, C6H6? a) H2O b) CH3OH (methyl alcohol) c) HCl d) CCl4 8. Identify the INCORRECT statement: a) Supersaturated solutions are metastable. b) Heating a solution of O2 gas in water drives O2 out of the solution. c) Substances have a higher solubility in a solvent when the temperature is increased. d) Increasing the partial pressure of a gas over a liquid increases the amount of gas dissolved. e) Increasing the temperature of a solvent increases the rate of solution formation. 9. What is the molality of methanol in a solution that contains 256 g of CH3OH (methanol) in 125 grams of water? a) 2.05 mol/kg b) 2048 mol/kg c) 113.8 mol/kg d) 0.064 mol/kg e) 64 mol/kg 10. What is the mole fraction of methanol in the solution in Problem #9? a) 0.535 b) 8.00 c) 1.15 d) 0.867 e) 0.672 11. Solutions that follow the simple Raoult's Law equation exactly are called: a) colligative solutions b) colloids c) hydrophilic d) ideal solutions e) nonvolatile solutions 12. A colloidal suspension in which as gas is dispersed into a liquid solvent medium is called a: a) aerosol b) gel c) emulsion d) foam 13. The addition of a nonvolatile solute into a liquid solvent: a) lowers the boiling point. b) raises the freezing point. c) lowers the vapor pressure. d) all of the above. 14. Identify the INCORRECT statement: a) Boiling occurs when the vapor pressure of a liquid equals the surrounding pressure. b) Each solvent has its own particular freezing point depression constant that does not depend on the identity of the solute. c) Ethylene glycol in the car radiator lowers the freezing point of the coolant liquid and raises the boiling point. d) Increasing the temperature of a liquid increases its vapor pressure. e) A .10 molal solution of NaCl in water would have the same boiling point as 0.10 glucose molal solution. 15. What is the freezing point of a solution in which 20.0 grams of sucrose (C12H22O12) is dissolved in 400 grams of water? Kf = 1.86 °C/molal for water. a) -0.26 °C b) -0.10 °C c) 100.028 d) 0.52 °C e) -5.12 °C 16. Suppose 5.056 grams of an unknown solute are dissolved in 50.0 grams of phenol (C6H5OH). The resulting solution boils at 185.0 °C. What is the molecular weight of the unknown solute? The boiling point of pure phenol is 182 °C, and its boiling point constant Kb = 3.56 °C/molal. a) 0.120 g/mol b) 120 g/mol c) 0.168 g/mol d) 42.3 g/mol e) 168 g/mol 17. Colloids can be distinguished from true solution by: a) the sizes of the dispersed particles. b) the fact that no settling out occurs. c) the dispersing medium. d) the hydrophilic nature of the medium. KEY 1)d 2)b 3)a 4)c 5)a 6)b 7)d 8)c 9)e 10)a 11)d 12)d 13)c 14)e 15)a 16)b 17)a