Exam 11: Properties of Solutions Their Concentrations and Colligative Properties

When 211.6 g of a waxy substance was dissolved in 1.500 kg of carbon tetrachloride (CCl₄,153.8 g/mol, K_f = 29.8 $\degree$ C/m), the freezing point dropped by 9.81 $\degree$ C.What is the approximate molar mass of the substance?

Intravenously administered saline solution must have an osmotic pressure that matches that of blood to prevent hemolysis or crenation of blood cells.What mass of sodium chloride (58.44 g/mol) is needed to produce 100.0 mL of saline solution with an osmotic pressure of 7.83 atm at a body temperature of 37 $\degree$ C?

Indicate which aqueous solution has the fastest evaporation rate.

Which of the following pairs of liquids probably exhibits very nearly ideal behavior when mixed?

Ethylene glycol is used in automobile radiators as an antifreeze.Use the following information to determine the freezing point of an antifreeze solution made by mixing 2.5 L of ethylene glycol with 2.5 L of water.Ethylene glycol is essentially nonvolatile and does not dissociate in water.molar mass of ethylene glycol = 62.07 g/mol Density of ethylene glycol=1.11 g/mL Density of water =1.00 g/mL K_f for water =1.86 $\degree$ C kg/mol

A solution is prepared by adding 1.50 mol of glucose, which is not volatile, to 3.50 mol of water.What is the vapor pressure of this solution at 25 $\degree$ C given that the vapor pressure of pure water is 23.8 torr?

You wish to prepare a solution of methanol (CH₃OH, 32.04 g/mol) and ethanol (CH₃CH₂OH, 46.07 g/mol) that has a total vapor pressure of 66 torr at 20 $\degree$ C.Calculate the mole fraction of ethanol in the solution that will produce the desired pressure.

A solution is prepared by mixing 50.00 g of methanol (CH₃OH, 32.04 g/mol) with 50.00 g of ethanol (CH₃CH₂OH, 46.07 g/mol).Use the following data to determine the vapor pressure of this solution at 20 $\degree$ C.

You have learned that adding table salt, NaCl (58.44 g/mol, 2.16 g/cm³), to water (K_b = 0.52oC/m) increases the temperature at which it boils.You decide to try cooking pasta faster at a higher temperature in boiling salty water.What increase in the boiling point do you expect if you add 4 tablespoons (1 tbsp = 14.8 cm³) of salt to 16 oz of water (474 mL)?

Describe how you would use the data obtained by a measurement of osmotic pressure to determine the molar mass of a compound.

Magnesium chloride is often used to melt ice on sidewalks.Considering that the solubility of magnesium chloride 95.21 (g/mol) in water is 54.3 g per 100.0 g of water, what is the lowest temperature that you would expect to be able to melt ice with magnesium chloride? Assume ideal behavior.(K_f (water) =1.86 $\degree$ C/m)

Which statement is NOT correct? Determination of the molar mass of an unknown sample by an osmotic pressure measurement requires that

A 1.00 L aqueous magnesium chloride solution has an osmotic pressure of 15.4 atm at 25 $\degree$ C.How many grams of MgCl₂ (95.21 g/mol) were required to make this solution?

A solution of 5.00 g of sodium chloride in 1.00 kg of water has a freezing point of -0.299 $\degree$ C.What is the actual van 't Hoff factor for this salt at this concentration? (K_f (water) = 1.86 $\degree$ C/m)

Determine the molarity of an aspirin solution that produces an osmotic pressure of 0.0555 atm at 25 $\degree$ C (i = 1).

A 4.028 m aqueous ethylene glycol (C₂H₆O₂, 62.07 g/mol) solution has a density of about 1.024 g/mL at 20 $\degree$ C.How many mL of solution contain 25.0 g of C₂H₆O₂?

Cholesterol is poorly soluble in water, but it will dissolve in nonpolar solvents such as cyclohexane (C₆H₁₂, 84.18 g/mol, K_f = 20.2 $\degree$ C/m, T_f = 6.55 $\degree$ C).When 10.0 g cholesterol was dissolved in 0.500 kg cyclohexane, the freezing point of the solution was 5.50 $\degree$ C.What is the approximate molar mass of cholesterol?

You are working as a research intern in a biochemistry lab, and you synthesize a new protein.You decide to use osmosis to determine your protein's molar mass.You dissolve 0.120 g of the protein in water to make 20.00 mL of solution, and the osmotic pressure is 3.53 torr at 298 K.You report that the molar mass is _______ g/mol.

Isopropyl alcohol, (CH₃)₂CHOH, has a molar enthalpy of vaporization of 44.0 kJ/mol and a normal boiling point of 82.5 $\degree$ C.Estimate the temperature at which isopropyl alcohol would have a vapor pressure of 100.0 Torr.

Which of the following regarding the vapor pressure of a solution containing a nonvolatile solute is NOT correct?