. Assume complete dissociation ofthe salt and ideal behavior of the solution.Correct answer: 0.252824◦C.Explanation:mNaNO3= 20 gmwater= 953 gKbwater = 0.512◦C/mNaNO3→Na++ NO−3i= 2m= (20 g NaNO3)parenleftBig1 mol NaNO385.0 g NaOHparenrightBig= 0.235294 mol NaNO3ΔTb=Kb·m·i=parenleftbigg0.512◦Cmparenrightbigg parenleftbigg0.2352940.953mparenrightbigg(2)= 0.252824◦C01910.0 points
Version 147 – hw02 – McCord – (53580)6Two aqueous solutions are separated by amembrane permeable only to water.Solution A is a 0.34 M KCl solution; andSolution B is a 0.64 M KCl solution.Which of the following statements is TRUE?1.For a reverse osmosis process, pressuremust be applied to solution A.2.Pressure must be applied to solutionA to create an equilibrium flow of watermolecules.3.K+ions flow from solution B to solutionA.4.H2O molecules flow from solution A tosolution B.correct5.Cl−ions flow from solution B to solutionA.Explanation:Here the membrane is only permeable towater, so only H2O can pass from solutionA to solution B (or vice versa).As solutionA islessconcentrated than solution B, H2Omolecules will spontaneously travelfromso-lution Atosolution B in order to make theconcentrations of the two solutions equal.02010.0 pointsAsolutionof1gofanunknownnon-electrolyte in 673 mL of water at 31.6◦C hasan osmotic pressure of 30 torr.What is themolecular weight of this solute? Neglect thevolume due to solute.Correct answer: 940.89 g/mol.Explanation:msolute= 1 gVsoln= 673 mL = 0.673 LT= 31.6◦C + 273 = 304.6 Kπ= 30 torr×1 atm760 torr= 0.0394737 atmThe osmotic pressureπ=M R T=parenleftBignVparenrightBigR T=msoluteMWVsolnR TMW =mR TV π=(1 g)(0.08206atm·Lmol·K)(304.6 K)(0.673 L)(0.0394737 atm)= 940.89 g/molAlternate Solution:M=πR T=0.0394737 atm(0.08206atm·Lmol·K)(304.6 K)= 0.00157923 mol/L? mol = (conc)(vol)= (0.00157923 mol/L)(0.673 L)= 0.00106282 molMW =gmol=1 g0.00106282 mol= 940.89 g/mol02110.0 pointsThe following diagram shows a solution on theleft (dark shade) and just the solvent on theright (light shade) separated by a semiperme-able membrane.Which of the following diagrams best rep-resents the final state of this system afterequilibrium is achieved?1.correct2.
Version 147 – hw02 – McCord – (53580)73.4.5.Explanation:Only the solvent goes through the mem-brane thus increasing the volume on the solu-tion side and decreasing volume on the solventside.The solution side is therefore dilutedslightly and the shade is lightened somewhat.The solute itself (the darker color) cannotpass through the membrane so the right sideMUST also stay the same color of pure solvent(the lighest shade shown).02210.0 pointsPurenitrobenzeneboilsat210.88◦Candfreezes at 5.70◦C. It has a boiling point el-evation constant of 5.24 and a freezing pointdepression constant of 7.00, both expressed inunits of◦C and molality. A solution of an un-known solute dissolved in nitrobenzene boilsat 214.48◦C.At what temperature in◦C,would this solution freeze? Assume that thesolute is not volatile and does not ionize anddoes not associate in the solution.