PRACTICE MINI EXAM 3 The exam will cover material from Chapter 10 homework and any other topic cover during class and discussion The questions in this practice exam are of similar difficulty to those in the actual exam however the questions will not be the same I 1 Dissolving a solute such as KOH in a solvent such as water results in A an increase in the melting point of the liquid B a decrease in the boiling point of the liquid C a decrease in the vapor pressure of the liquid D no change in the boiling point of the liquid Multiple choice 2 Which statement is false A The vapor pressure of a solvent over a solution decreases as its mole fraction increases B The solubility of a gas increases as the temperature increases C The vapor pressure of a solvent over a solution is less than that of the pure solvent D The greater the pressure over a solution the greater the solubility of a gas in the solution E Ionic solutes dissociate in aqueous solution magnifying colligative properties relative to those of nonelectrolytes methanol A 0 0348 m 3 If 26 5 g of methanol CH3OH is added to 735 g of water what is the molality of the B 2 03 m C 1 13 m D 3 61 m 4 Henry s law states that gas solubility is A directly proportional to temperature of the solution B directly proportional to the pressure of the gas over the solution C inversely proportional to the combined pressure of all gases over the solution D inversely proportional to the pressure of the gas over the solution 5 What mass of ethylene glycol when mixed with 225 g H2O will reduce the equilibrium vapor pressure of H2O from 1 00 atm to 0 800 atm at 100 C The molar masses of water and ethylene glycol are 18 02 g mol and 62 07 g mol respectively Assume ideal behavior for the solution A 15 6 g B 49 9 g C 194 g D 969 g 6 Which of the following electrolytes has largest van t Hoff factor i A CaCl2 B Na3PO4 C KClO4 D NaNO3 7 which of the following statements concerning osmosis is are CORRECT 1 Osmosis involves the movement of a solvent through a semipermeable membrane 2 Solvents move from regions of high solute concentration to regions of lower solute concentration 3 Osmotic pressure is a colligative property A 1 only B 2 only C 1 and 3 D 1 2 and 3 8 A solution is prepared by dissolving 5 00 g of an unknown molecular solid in water to make 1 00 L of solution The osmotic pressure of the solution is 1 61 atm at 25 C What is the molar mass of the solute A 6 37 g mol B 58 44 g mol C 76 0 g mol D 102 g mol 9 What volume of 6 0 M HNO3 is required to prepare 250 mL of 0 40 M HNO3 A 9 7 mL B 17 mL C 27 mL D 38 mL 10 Red blood cells are placed into three solutions each solution a different concentration of NaCl One solution is isotonic one is hypotonic and one is hypertonic with red blood cells Solution A is and solution C is with the red blood cells Solution A Solution B Solution C A hypertonic isotonic B isotonic hypertonic C hypotonic isotonic D isotonic hypotonic E hypotonic hypertonic 11 Which of these 0 1 M aqueous solutions will have the lowest vapor pressure A C6H12O6 C Na2SO4 B MgSO4 D KCl II Problem Solving show all your work No work no credit 12 Rank the following compounds in order of increasing vapor pressure at 298 K A CH3CH2OH B CH3OCH3 C CH3CH2CH3 13 Human blood has a molar concentration of solutes of 0 30 M What is the osmotic pressure of blood at 25 C 14 A solution is prepared by dissolving 50 0 g of hemoglobin Hb in enough water to make 1 00 L of solution The osmotic pressure of the solution is measured and found to be 14 3 mmHg at 25 C Calculate the molar mass of hemoglobin Assume that there is no change in volume when the hemoglobin is added to water 15 A laboratory experiment on colligative properties direct students to determine the molar mass of an unknown sample nonelectrolyte One of the students dissolved 4 50 g of the unknown into a water ice mixture to determine the freezing point of the solution the freezing point of the solution was measured as 2 8 C and the mass of the solution after removal of the ice was weight and recorded as 65 00 g For water kf 1 86 m C a What is the molality of the solution b What is the molar mass of the unknown solid Equations and Data Sheet Molarity mole volume PV nRT R 0 0821 760 mmHg 1 atm XA nA nT Henry s law Cg kPg R 0 0821 molality m moles of solute kilograms solvent PA XA PA Psolution Xsolvent P solvent Molar mass mass mols density mass volume T t C 273 K McVc MdVd Pressure units 1 bar 1 X 105 Pa R units R 8 31 1 atm 101325 Pa 760 mmHg 760 Torr 14 7 psi R 8 31 J mol K 8 31 m3 Pa mol K 0 08206 L atm mol K 2 1 1 1 1 2 12111PXPPXP ffbbmkTmkT iMRTimkTimkTbbff Practice Mini Exam 3 AK 1 C 2 A 3 C 4 B 5 C 6 B 7 C 8 C 9 B 10 B 11 C 12 A B C 13 7 3 atm Use MRT 14 MM 65019 5 g mol use 15 m 1 5molal and MM 50 g mol use Tf mKf