Explanation:020(part 1 of 1) 10 pointsThe vapor pressure of water at 37◦C is 47.1torr and its enthalpy of vaporization is 44.0kJ·mol-1. Estimate the vapor pressure of wa-ter at 87◦C. Assume the enthalpy of vaporiza-tion of water is independent of temperature.1.713 torr2.504 torrcorrect3.112 torr4.256 torr5.52 torrExplanation:021(part 1 of 1) 10 pointsConsider the temperature composition dia-gram of a binary mixture of A and B whichforms a minimum boiling azeotrope: InitiallyXA= 0.6.00.20.40.60.81.0020406080100120140XAboiling temperature (◦C)Which of the following is true if the distil-late is collected from a distillation apparatuswhile the solution boils?1.XAin the beakerwill remain the same.2.XAin the beakerwill approach 0.3.XAin the beakerwill approach 1.4.XAin the beakerwill approach 0.3.cor-rectExplanation:022(part 1 of 1) 10 pointsMixing 17.6 kg of ethylene glycol (commercialantifreeze, C2H6O2) with 6.00 gal of waterlowers the freezing point to-10.0◦F. Supposeyou wanted to accomplish the same thing withsugar (sucrose, C12H22O11) instead of ethy-lene glycol.How many kilograms of sucrosewould you use? 1 gallon = 3.785 liters.Kfforwater = 1.86◦C/m.1.3.09 kg2.97.1 kgcorrect
Thompson, Margaret – Exam 1 – Due: Sep 18 2007, 3:00 pm – Inst: James Holcombe83.4.68×10-3kg4.17.6 kg5.6019 kgExplanation:023(part 1 of 1) 10 pointsSeveralinterestingobservationsfromtheworld around you are listed below.Whichof these is NOT explained by a colligativeproperty?1.Water boils at a higher temperature whensalt is added.2.Antifreeze is added to a car radiator tokeep the car from overheating.3.The freezing point of water is loweredwhen salt is added.4.A lobster will die when placed in freshwater.5.At high altitude it takes longer to cookspaghetti.correctExplanation:Colligative properties of a solution dependon the number of solute particles in solution,not the type.Boiling point variations dueto pressure changes have nothing to do withsolutions and colligative properties (boilingpoint variations due to particles in solution,etc.).024(part 1 of 3) 10 pointsConsider the following pressure diagram for abinary liquid containing A and B.01xA70 torr20 torrIf 8 mol of A and 8 mol of B are mixed,what is the vapor pressure of B?1.20 torr2.35 torrcorrect3.45 torr4.10 torr5.70 torrExplanation:The mole fraction of A isxA=mol Atotal mol=8 mol8 mol + 8 mol= 0.5.010.520 torr35 torr025(part 2 of 3) 10 pointsWhat is the corresponding vapor pressure ofA?1.35 torr2.10 torrcorrect3.20 torr4.45 torr
Thompson, Margaret – Exam 1 – Due: Sep 18 2007, 3:00 pm – Inst: James Holcombe95.70 torrExplanation:010.520 torr10 torr026(part 3 of 3) 10 pointsWhat is the corresponding total vapor pres-sure?1.20 torr2.35 torr3.45 torrcorrect4.70 torr5.10 torrExplanation:010.520 torr45 torr027(part 1 of 1) 10 pointsArrange H2O, NH3, Ar, and NaCl in order ofexpected increasing boiling points.