How many moles of urea (60. g/mol) must be dissolved in 65.3 g of water to give a 3.2 m solution? A) 3.2 mol B) 0.21 mol C) 0.0032 mol D) 9.2 times 10^2 mol E) 1.9 times 10^2 mol What is the boiling-point change for a solution containing 0.591 mol of naphthalene (a nonvolatile, nonionizing compound) in 250, g of liquid benzene? (K_b = 2.53 degree C/m for benzene) A) 1.07 degree C B) 4.28 degree C C) 0.374 degree C D) 5.98 degree C E) 1.495 degree C When a 31.2-g sample of an unknown compound is dissolved in 500. g of benzene, the freezing point of the resulting solution is 3.77 degree C. The freezing point of pure benzene is 5.48 degree C, and K_f for benzene is 5. l2 degree C/m. Calculate the molar mass of the unknown compound. A) 18.2 g/mol B) 374 g/mol C) 93.4 g/mol D)187.gmol E) 160 g/mol A solute added lo a solvent raises the boiling point of the solution because A) the solute particles raise the solvent's vapor pressure, thus requiring a higher temperature to cause boiling. B) the temperature to cause boiling must be great enough to boil not only the solvent but also the solute. C) the solute increases the volume of the solution, and an increase in volume requires an increase in the temperature lo reach the boiling point (derived from PV= nRT). D) the solute particles lower the solvent's vapor pressure, thus requiring a higher temperature to cause boiling. E) two of these explanations are correct.