Problem Set 4 Chapter 14 1 Ethanol C2H5OH and water H2O are both liquids at or near room temperature When a sample of ethanol is poured into a beaker containing water the two liquids a are miscible because each can hydrogen bond with the other b are immiscible because each has strong hydrogen bonds that cannot be broken c are miscible because both are liquids and all liquids are miscible d are immiscible because organic and non organic compounds cannot mix 2 If exactly 100 0 grams of NaCl molecular mass 58 44 g mol are dissolved in 300 grams of water molecular mass 18 02 g mol the mole fraction of NaCl is 3 When 7 50 grams of iodine I2 is added to 48 7 grams of carbon tetrachloride CCl4 the iodine dissolves and a solution is formed The weight percent of the iodine in the solution is a 1 71 b 0 0932 c 0 250 d 0 103 e 4 75 a 13 3 b 15 6 c 60 7 d 2 96 e 86 0 4 In comparing the phase diagram for water with that of a solution of sugar in water all of the following decrease except a the vapor pressure b the boiling point 5 Benzene freezes at 5 45oC The Kf for benzene is 5 07 oC m What would be the freezing point of a 0 210m solution of octane in benzene 6 How many grams of water are needed to dissolve 27 8 g of NH4NO3 80 0 g mol in order to prepare a 0 452 m molal solution c the freezing point d the triple point a 1 06oC b 4 39oC c 6 51oC d 10 52oC e 5 80oC a 769 g b 36 2 g c 972 g d 34 8 g e 157 g 7 If all ionic substances are completely ionized the aqueous solution with the lowest freezing point would be a 0 25 m NH4NO3 b 0 30 m BaCl2 c 0 35 m LiBr d 0 50 m sucrose e 0 40 m MgSO4 8 For electrolyte solutions the the concentration of the electrolyte and the the ion charges then the the ion pairing a lower smaller greater b higher smaller smaller c higher greater greater d lower greater smaller e lower greater greater a 31 0 g mol b 62 1 g mol c 124 g mol d 248 g mol e 372 g mol 9 A solution was made by dissolving 62 07 grams of a compound in 500 0 g of water The compound was not ionic The freezing point of the solution was measured and found to be exactly equal to one half of the Kfp value for water What is the molar mass of this compound 10 The molecular mass of a substance was determined by the freezing point depression technique The minimum data required for the determination the molar mass are a Tf and Kf only b Tf Kf and mass of solute c Tf Kf mass of solute and mass of solvent d Tf Kf mass of solute mass of solvent and identity of solvent e Tf Kf mass of solute mass of solvent and identity of solvent and solute ANSWERS 1 A 2 B 3 A 4 B 5 B 6 A 7 B 8 C 9 D 10 C